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Based on kernel version 3.9. Page generated on 2013-05-02 23:06 EST.
1 ------------------------------------------------------------------------------ 2 T H E /proc F I L E S Y S T E M 3 ------------------------------------------------------------------------------ 4 /proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999 5 Bodo Bauer <bb@ricochet.net> 6 7 2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 8 move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 9 ------------------------------------------------------------------------------ 10 Version 1.3 Kernel version 2.2.12 11 Kernel version 2.4.0-test11-pre4 12 ------------------------------------------------------------------------------ 13 fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 14 15 Table of Contents 16 ----------------- 17 18 0 Preface 19 0.1 Introduction/Credits 20 0.2 Legal Stuff 21 22 1 Collecting System Information 23 1.1 Process-Specific Subdirectories 24 1.2 Kernel data 25 1.3 IDE devices in /proc/ide 26 1.4 Networking info in /proc/net 27 1.5 SCSI info 28 1.6 Parallel port info in /proc/parport 29 1.7 TTY info in /proc/tty 30 1.8 Miscellaneous kernel statistics in /proc/stat 31 1.9 Ext4 file system parameters 32 33 2 Modifying System Parameters 34 35 3 Per-Process Parameters 36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer 37 score 38 3.2 /proc/<pid>/oom_score - Display current oom-killer score 39 3.3 /proc/<pid>/io - Display the IO accounting fields 40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 41 3.5 /proc/<pid>/mountinfo - Information about mounts 42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 43 3.7 /proc/<pid>/task/<tid>/children - Information about task children 44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 45 46 4 Configuring procfs 47 4.1 Mount options 48 49 ------------------------------------------------------------------------------ 50 Preface 51 ------------------------------------------------------------------------------ 52 53 0.1 Introduction/Credits 54 ------------------------ 55 56 This documentation is part of a soon (or so we hope) to be released book on 57 the SuSE Linux distribution. As there is no complete documentation for the 58 /proc file system and we've used many freely available sources to write these 59 chapters, it seems only fair to give the work back to the Linux community. 60 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 61 afraid it's still far from complete, but we hope it will be useful. As far as 62 we know, it is the first 'all-in-one' document about the /proc file system. It 63 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 64 SPARC, AXP, etc., features, you probably won't find what you are looking for. 65 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 66 additions and patches are welcome and will be added to this document if you 67 mail them to Bodo. 68 69 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 70 other people for help compiling this documentation. We'd also like to extend a 71 special thank you to Andi Kleen for documentation, which we relied on heavily 72 to create this document, as well as the additional information he provided. 73 Thanks to everybody else who contributed source or docs to the Linux kernel 74 and helped create a great piece of software... :) 75 76 If you have any comments, corrections or additions, please don't hesitate to 77 contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this 78 document. 79 80 The latest version of this document is available online at 81 http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 82 83 If the above direction does not works for you, you could try the kernel 84 mailing list at linux-kernel@vger.kernel.org and/or try to reach me at 85 comandante@zaralinux.com. 86 87 0.2 Legal Stuff 88 --------------- 89 90 We don't guarantee the correctness of this document, and if you come to us 91 complaining about how you screwed up your system because of incorrect 92 documentation, we won't feel responsible... 93 94 ------------------------------------------------------------------------------ 95 CHAPTER 1: COLLECTING SYSTEM INFORMATION 96 ------------------------------------------------------------------------------ 97 98 ------------------------------------------------------------------------------ 99 In This Chapter 100 ------------------------------------------------------------------------------ 101 * Investigating the properties of the pseudo file system /proc and its 102 ability to provide information on the running Linux system 103 * Examining /proc's structure 104 * Uncovering various information about the kernel and the processes running 105 on the system 106 ------------------------------------------------------------------------------ 107 108 109 The proc file system acts as an interface to internal data structures in the 110 kernel. It can be used to obtain information about the system and to change 111 certain kernel parameters at runtime (sysctl). 112 113 First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 114 show you how you can use /proc/sys to change settings. 115 116 1.1 Process-Specific Subdirectories 117 ----------------------------------- 118 119 The directory /proc contains (among other things) one subdirectory for each 120 process running on the system, which is named after the process ID (PID). 121 122 The link self points to the process reading the file system. Each process 123 subdirectory has the entries listed in Table 1-1. 124 125 126 Table 1-1: Process specific entries in /proc 127 .............................................................................. 128 File Content 129 clear_refs Clears page referenced bits shown in smaps output 130 cmdline Command line arguments 131 cpu Current and last cpu in which it was executed (2.4)(smp) 132 cwd Link to the current working directory 133 environ Values of environment variables 134 exe Link to the executable of this process 135 fd Directory, which contains all file descriptors 136 maps Memory maps to executables and library files (2.4) 137 mem Memory held by this process 138 root Link to the root directory of this process 139 stat Process status 140 statm Process memory status information 141 status Process status in human readable form 142 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan 143 pagemap Page table 144 stack Report full stack trace, enable via CONFIG_STACKTRACE 145 smaps a extension based on maps, showing the memory consumption of 146 each mapping and flags associated with it 147 .............................................................................. 148 149 For example, to get the status information of a process, all you have to do is 150 read the file /proc/PID/status: 151 152 >cat /proc/self/status 153 Name: cat 154 State: R (running) 155 Tgid: 5452 156 Pid: 5452 157 PPid: 743 158 TracerPid: 0 (2.4) 159 Uid: 501 501 501 501 160 Gid: 100 100 100 100 161 FDSize: 256 162 Groups: 100 14 16 163 VmPeak: 5004 kB 164 VmSize: 5004 kB 165 VmLck: 0 kB 166 VmHWM: 476 kB 167 VmRSS: 476 kB 168 VmData: 156 kB 169 VmStk: 88 kB 170 VmExe: 68 kB 171 VmLib: 1412 kB 172 VmPTE: 20 kb 173 VmSwap: 0 kB 174 Threads: 1 175 SigQ: 0/28578 176 SigPnd: 0000000000000000 177 ShdPnd: 0000000000000000 178 SigBlk: 0000000000000000 179 SigIgn: 0000000000000000 180 SigCgt: 0000000000000000 181 CapInh: 00000000fffffeff 182 CapPrm: 0000000000000000 183 CapEff: 0000000000000000 184 CapBnd: ffffffffffffffff 185 Seccomp: 0 186 voluntary_ctxt_switches: 0 187 nonvoluntary_ctxt_switches: 1 188 189 This shows you nearly the same information you would get if you viewed it with 190 the ps command. In fact, ps uses the proc file system to obtain its 191 information. But you get a more detailed view of the process by reading the 192 file /proc/PID/status. It fields are described in table 1-2. 193 194 The statm file contains more detailed information about the process 195 memory usage. Its seven fields are explained in Table 1-3. The stat file 196 contains details information about the process itself. Its fields are 197 explained in Table 1-4. 198 199 (for SMP CONFIG users) 200 For making accounting scalable, RSS related information are handled in 201 asynchronous manner and the vaule may not be very precise. To see a precise 202 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 203 It's slow but very precise. 204 205 Table 1-2: Contents of the status files (as of 2.6.30-rc7) 206 .............................................................................. 207 Field Content 208 Name filename of the executable 209 State state (R is running, S is sleeping, D is sleeping 210 in an uninterruptible wait, Z is zombie, 211 T is traced or stopped) 212 Tgid thread group ID 213 Pid process id 214 PPid process id of the parent process 215 TracerPid PID of process tracing this process (0 if not) 216 Uid Real, effective, saved set, and file system UIDs 217 Gid Real, effective, saved set, and file system GIDs 218 FDSize number of file descriptor slots currently allocated 219 Groups supplementary group list 220 VmPeak peak virtual memory size 221 VmSize total program size 222 VmLck locked memory size 223 VmHWM peak resident set size ("high water mark") 224 VmRSS size of memory portions 225 VmData size of data, stack, and text segments 226 VmStk size of data, stack, and text segments 227 VmExe size of text segment 228 VmLib size of shared library code 229 VmPTE size of page table entries 230 VmSwap size of swap usage (the number of referred swapents) 231 Threads number of threads 232 SigQ number of signals queued/max. number for queue 233 SigPnd bitmap of pending signals for the thread 234 ShdPnd bitmap of shared pending signals for the process 235 SigBlk bitmap of blocked signals 236 SigIgn bitmap of ignored signals 237 SigCgt bitmap of catched signals 238 CapInh bitmap of inheritable capabilities 239 CapPrm bitmap of permitted capabilities 240 CapEff bitmap of effective capabilities 241 CapBnd bitmap of capabilities bounding set 242 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) 243 Cpus_allowed mask of CPUs on which this process may run 244 Cpus_allowed_list Same as previous, but in "list format" 245 Mems_allowed mask of memory nodes allowed to this process 246 Mems_allowed_list Same as previous, but in "list format" 247 voluntary_ctxt_switches number of voluntary context switches 248 nonvoluntary_ctxt_switches number of non voluntary context switches 249 .............................................................................. 250 251 Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 252 .............................................................................. 253 Field Content 254 size total program size (pages) (same as VmSize in status) 255 resident size of memory portions (pages) (same as VmRSS in status) 256 shared number of pages that are shared (i.e. backed by a file) 257 trs number of pages that are 'code' (not including libs; broken, 258 includes data segment) 259 lrs number of pages of library (always 0 on 2.6) 260 drs number of pages of data/stack (including libs; broken, 261 includes library text) 262 dt number of dirty pages (always 0 on 2.6) 263 .............................................................................. 264 265 266 Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 267 .............................................................................. 268 Field Content 269 pid process id 270 tcomm filename of the executable 271 state state (R is running, S is sleeping, D is sleeping in an 272 uninterruptible wait, Z is zombie, T is traced or stopped) 273 ppid process id of the parent process 274 pgrp pgrp of the process 275 sid session id 276 tty_nr tty the process uses 277 tty_pgrp pgrp of the tty 278 flags task flags 279 min_flt number of minor faults 280 cmin_flt number of minor faults with child's 281 maj_flt number of major faults 282 cmaj_flt number of major faults with child's 283 utime user mode jiffies 284 stime kernel mode jiffies 285 cutime user mode jiffies with child's 286 cstime kernel mode jiffies with child's 287 priority priority level 288 nice nice level 289 num_threads number of threads 290 it_real_value (obsolete, always 0) 291 start_time time the process started after system boot 292 vsize virtual memory size 293 rss resident set memory size 294 rsslim current limit in bytes on the rss 295 start_code address above which program text can run 296 end_code address below which program text can run 297 start_stack address of the start of the main process stack 298 esp current value of ESP 299 eip current value of EIP 300 pending bitmap of pending signals 301 blocked bitmap of blocked signals 302 sigign bitmap of ignored signals 303 sigcatch bitmap of catched signals 304 wchan address where process went to sleep 305 0 (place holder) 306 0 (place holder) 307 exit_signal signal to send to parent thread on exit 308 task_cpu which CPU the task is scheduled on 309 rt_priority realtime priority 310 policy scheduling policy (man sched_setscheduler) 311 blkio_ticks time spent waiting for block IO 312 gtime guest time of the task in jiffies 313 cgtime guest time of the task children in jiffies 314 start_data address above which program data+bss is placed 315 end_data address below which program data+bss is placed 316 start_brk address above which program heap can be expanded with brk() 317 arg_start address above which program command line is placed 318 arg_end address below which program command line is placed 319 env_start address above which program environment is placed 320 env_end address below which program environment is placed 321 exit_code the thread's exit_code in the form reported by the waitpid system call 322 .............................................................................. 323 324 The /proc/PID/maps file containing the currently mapped memory regions and 325 their access permissions. 326 327 The format is: 328 329 address perms offset dev inode pathname 330 331 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test 332 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 333 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] 334 a7cb1000-a7cb2000 ---p 00000000 00:00 0 335 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 336 a7eb2000-a7eb3000 ---p 00000000 00:00 0 337 a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack:1001] 338 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 339 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 340 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 341 a800b000-a800e000 rw-p 00000000 00:00 0 342 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 343 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 344 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 345 a8024000-a8027000 rw-p 00000000 00:00 0 346 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 347 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 348 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 349 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 350 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 351 352 where "address" is the address space in the process that it occupies, "perms" 353 is a set of permissions: 354 355 r = read 356 w = write 357 x = execute 358 s = shared 359 p = private (copy on write) 360 361 "offset" is the offset into the mapping, "dev" is the device (major:minor), and 362 "inode" is the inode on that device. 0 indicates that no inode is associated 363 with the memory region, as the case would be with BSS (uninitialized data). 364 The "pathname" shows the name associated file for this mapping. If the mapping 365 is not associated with a file: 366 367 [heap] = the heap of the program 368 [stack] = the stack of the main process 369 [stack:1001] = the stack of the thread with tid 1001 370 [vdso] = the "virtual dynamic shared object", 371 the kernel system call handler 372 373 or if empty, the mapping is anonymous. 374 375 The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint 376 of the individual tasks of a process. In this file you will see a mapping marked 377 as [stack] if that task sees it as a stack. This is a key difference from the 378 content of /proc/PID/maps, where you will see all mappings that are being used 379 as stack by all of those tasks. Hence, for the example above, the task-level 380 map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this: 381 382 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test 383 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 384 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] 385 a7cb1000-a7cb2000 ---p 00000000 00:00 0 386 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 387 a7eb2000-a7eb3000 ---p 00000000 00:00 0 388 a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack] 389 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 390 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 391 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 392 a800b000-a800e000 rw-p 00000000 00:00 0 393 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 394 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 395 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 396 a8024000-a8027000 rw-p 00000000 00:00 0 397 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 398 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 399 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 400 aff35000-aff4a000 rw-p 00000000 00:00 0 401 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 402 403 The /proc/PID/smaps is an extension based on maps, showing the memory 404 consumption for each of the process's mappings. For each of mappings there 405 is a series of lines such as the following: 406 407 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 408 Size: 1084 kB 409 Rss: 892 kB 410 Pss: 374 kB 411 Shared_Clean: 892 kB 412 Shared_Dirty: 0 kB 413 Private_Clean: 0 kB 414 Private_Dirty: 0 kB 415 Referenced: 892 kB 416 Anonymous: 0 kB 417 Swap: 0 kB 418 KernelPageSize: 4 kB 419 MMUPageSize: 4 kB 420 Locked: 374 kB 421 VmFlags: rd ex mr mw me de 422 423 the first of these lines shows the same information as is displayed for the 424 mapping in /proc/PID/maps. The remaining lines show the size of the mapping 425 (size), the amount of the mapping that is currently resident in RAM (RSS), the 426 process' proportional share of this mapping (PSS), the number of clean and 427 dirty private pages in the mapping. Note that even a page which is part of a 428 MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used 429 by only one process, is accounted as private and not as shared. "Referenced" 430 indicates the amount of memory currently marked as referenced or accessed. 431 "Anonymous" shows the amount of memory that does not belong to any file. Even 432 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 433 and a page is modified, the file page is replaced by a private anonymous copy. 434 "Swap" shows how much would-be-anonymous memory is also used, but out on 435 swap. 436 437 "VmFlags" field deserves a separate description. This member represents the kernel 438 flags associated with the particular virtual memory area in two letter encoded 439 manner. The codes are the following: 440 rd - readable 441 wr - writeable 442 ex - executable 443 sh - shared 444 mr - may read 445 mw - may write 446 me - may execute 447 ms - may share 448 gd - stack segment growns down 449 pf - pure PFN range 450 dw - disabled write to the mapped file 451 lo - pages are locked in memory 452 io - memory mapped I/O area 453 sr - sequential read advise provided 454 rr - random read advise provided 455 dc - do not copy area on fork 456 de - do not expand area on remapping 457 ac - area is accountable 458 nr - swap space is not reserved for the area 459 ht - area uses huge tlb pages 460 nl - non-linear mapping 461 ar - architecture specific flag 462 dd - do not include area into core dump 463 mm - mixed map area 464 hg - huge page advise flag 465 nh - no-huge page advise flag 466 mg - mergable advise flag 467 468 Note that there is no guarantee that every flag and associated mnemonic will 469 be present in all further kernel releases. Things get changed, the flags may 470 be vanished or the reverse -- new added. 471 472 This file is only present if the CONFIG_MMU kernel configuration option is 473 enabled. 474 475 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 476 bits on both physical and virtual pages associated with a process. 477 To clear the bits for all the pages associated with the process 478 > echo 1 > /proc/PID/clear_refs 479 480 To clear the bits for the anonymous pages associated with the process 481 > echo 2 > /proc/PID/clear_refs 482 483 To clear the bits for the file mapped pages associated with the process 484 > echo 3 > /proc/PID/clear_refs 485 Any other value written to /proc/PID/clear_refs will have no effect. 486 487 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 488 using /proc/kpageflags and number of times a page is mapped using 489 /proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt. 490 491 1.2 Kernel data 492 --------------- 493 494 Similar to the process entries, the kernel data files give information about 495 the running kernel. The files used to obtain this information are contained in 496 /proc and are listed in Table 1-5. Not all of these will be present in your 497 system. It depends on the kernel configuration and the loaded modules, which 498 files are there, and which are missing. 499 500 Table 1-5: Kernel info in /proc 501 .............................................................................. 502 File Content 503 apm Advanced power management info 504 buddyinfo Kernel memory allocator information (see text) (2.5) 505 bus Directory containing bus specific information 506 cmdline Kernel command line 507 cpuinfo Info about the CPU 508 devices Available devices (block and character) 509 dma Used DMS channels 510 filesystems Supported filesystems 511 driver Various drivers grouped here, currently rtc (2.4) 512 execdomains Execdomains, related to security (2.4) 513 fb Frame Buffer devices (2.4) 514 fs File system parameters, currently nfs/exports (2.4) 515 ide Directory containing info about the IDE subsystem 516 interrupts Interrupt usage 517 iomem Memory map (2.4) 518 ioports I/O port usage 519 irq Masks for irq to cpu affinity (2.4)(smp?) 520 isapnp ISA PnP (Plug&Play) Info (2.4) 521 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 522 kmsg Kernel messages 523 ksyms Kernel symbol table 524 loadavg Load average of last 1, 5 & 15 minutes 525 locks Kernel locks 526 meminfo Memory info 527 misc Miscellaneous 528 modules List of loaded modules 529 mounts Mounted filesystems 530 net Networking info (see text) 531 pagetypeinfo Additional page allocator information (see text) (2.5) 532 partitions Table of partitions known to the system 533 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 534 decoupled by lspci (2.4) 535 rtc Real time clock 536 scsi SCSI info (see text) 537 slabinfo Slab pool info 538 softirqs softirq usage 539 stat Overall statistics 540 swaps Swap space utilization 541 sys See chapter 2 542 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 543 tty Info of tty drivers 544 uptime System uptime 545 version Kernel version 546 video bttv info of video resources (2.4) 547 vmallocinfo Show vmalloced areas 548 .............................................................................. 549 550 You can, for example, check which interrupts are currently in use and what 551 they are used for by looking in the file /proc/interrupts: 552 553 > cat /proc/interrupts 554 CPU0 555 0: 8728810 XT-PIC timer 556 1: 895 XT-PIC keyboard 557 2: 0 XT-PIC cascade 558 3: 531695 XT-PIC aha152x 559 4: 2014133 XT-PIC serial 560 5: 44401 XT-PIC pcnet_cs 561 8: 2 XT-PIC rtc 562 11: 8 XT-PIC i82365 563 12: 182918 XT-PIC PS/2 Mouse 564 13: 1 XT-PIC fpu 565 14: 1232265 XT-PIC ide0 566 15: 7 XT-PIC ide1 567 NMI: 0 568 569 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 570 output of a SMP machine): 571 572 > cat /proc/interrupts 573 574 CPU0 CPU1 575 0: 1243498 1214548 IO-APIC-edge timer 576 1: 8949 8958 IO-APIC-edge keyboard 577 2: 0 0 XT-PIC cascade 578 5: 11286 10161 IO-APIC-edge soundblaster 579 8: 1 0 IO-APIC-edge rtc 580 9: 27422 27407 IO-APIC-edge 3c503 581 12: 113645 113873 IO-APIC-edge PS/2 Mouse 582 13: 0 0 XT-PIC fpu 583 14: 22491 24012 IO-APIC-edge ide0 584 15: 2183 2415 IO-APIC-edge ide1 585 17: 30564 30414 IO-APIC-level eth0 586 18: 177 164 IO-APIC-level bttv 587 NMI: 2457961 2457959 588 LOC: 2457882 2457881 589 ERR: 2155 590 591 NMI is incremented in this case because every timer interrupt generates a NMI 592 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 593 594 LOC is the local interrupt counter of the internal APIC of every CPU. 595 596 ERR is incremented in the case of errors in the IO-APIC bus (the bus that 597 connects the CPUs in a SMP system. This means that an error has been detected, 598 the IO-APIC automatically retry the transmission, so it should not be a big 599 problem, but you should read the SMP-FAQ. 600 601 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 602 /proc/interrupts to display every IRQ vector in use by the system, not 603 just those considered 'most important'. The new vectors are: 604 605 THR -- interrupt raised when a machine check threshold counter 606 (typically counting ECC corrected errors of memory or cache) exceeds 607 a configurable threshold. Only available on some systems. 608 609 TRM -- a thermal event interrupt occurs when a temperature threshold 610 has been exceeded for the CPU. This interrupt may also be generated 611 when the temperature drops back to normal. 612 613 SPU -- a spurious interrupt is some interrupt that was raised then lowered 614 by some IO device before it could be fully processed by the APIC. Hence 615 the APIC sees the interrupt but does not know what device it came from. 616 For this case the APIC will generate the interrupt with a IRQ vector 617 of 0xff. This might also be generated by chipset bugs. 618 619 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are 620 sent from one CPU to another per the needs of the OS. Typically, 621 their statistics are used by kernel developers and interested users to 622 determine the occurrence of interrupts of the given type. 623 624 The above IRQ vectors are displayed only when relevant. For example, 625 the threshold vector does not exist on x86_64 platforms. Others are 626 suppressed when the system is a uniprocessor. As of this writing, only 627 i386 and x86_64 platforms support the new IRQ vector displays. 628 629 Of some interest is the introduction of the /proc/irq directory to 2.4. 630 It could be used to set IRQ to CPU affinity, this means that you can "hook" an 631 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 632 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 633 prof_cpu_mask. 634 635 For example 636 > ls /proc/irq/ 637 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 638 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 639 > ls /proc/irq/0/ 640 smp_affinity 641 642 smp_affinity is a bitmask, in which you can specify which CPUs can handle the 643 IRQ, you can set it by doing: 644 645 > echo 1 > /proc/irq/10/smp_affinity 646 647 This means that only the first CPU will handle the IRQ, but you can also echo 648 5 which means that only the first and fourth CPU can handle the IRQ. 649 650 The contents of each smp_affinity file is the same by default: 651 652 > cat /proc/irq/0/smp_affinity 653 ffffffff 654 655 There is an alternate interface, smp_affinity_list which allows specifying 656 a cpu range instead of a bitmask: 657 658 > cat /proc/irq/0/smp_affinity_list 659 1024-1031 660 661 The default_smp_affinity mask applies to all non-active IRQs, which are the 662 IRQs which have not yet been allocated/activated, and hence which lack a 663 /proc/irq/[0-9]* directory. 664 665 The node file on an SMP system shows the node to which the device using the IRQ 666 reports itself as being attached. This hardware locality information does not 667 include information about any possible driver locality preference. 668 669 prof_cpu_mask specifies which CPUs are to be profiled by the system wide 670 profiler. Default value is ffffffff (all cpus if there are only 32 of them). 671 672 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 673 between all the CPUs which are allowed to handle it. As usual the kernel has 674 more info than you and does a better job than you, so the defaults are the 675 best choice for almost everyone. [Note this applies only to those IO-APIC's 676 that support "Round Robin" interrupt distribution.] 677 678 There are three more important subdirectories in /proc: net, scsi, and sys. 679 The general rule is that the contents, or even the existence of these 680 directories, depend on your kernel configuration. If SCSI is not enabled, the 681 directory scsi may not exist. The same is true with the net, which is there 682 only when networking support is present in the running kernel. 683 684 The slabinfo file gives information about memory usage at the slab level. 685 Linux uses slab pools for memory management above page level in version 2.2. 686 Commonly used objects have their own slab pool (such as network buffers, 687 directory cache, and so on). 688 689 .............................................................................. 690 691 > cat /proc/buddyinfo 692 693 Node 0, zone DMA 0 4 5 4 4 3 ... 694 Node 0, zone Normal 1 0 0 1 101 8 ... 695 Node 0, zone HighMem 2 0 0 1 1 0 ... 696 697 External fragmentation is a problem under some workloads, and buddyinfo is a 698 useful tool for helping diagnose these problems. Buddyinfo will give you a 699 clue as to how big an area you can safely allocate, or why a previous 700 allocation failed. 701 702 Each column represents the number of pages of a certain order which are 703 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 704 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 705 available in ZONE_NORMAL, etc... 706 707 More information relevant to external fragmentation can be found in 708 pagetypeinfo. 709 710 > cat /proc/pagetypeinfo 711 Page block order: 9 712 Pages per block: 512 713 714 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 715 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 716 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 717 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 718 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 719 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 720 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 721 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 722 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 723 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 724 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 725 726 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 727 Node 0, zone DMA 2 0 5 1 0 728 Node 0, zone DMA32 41 6 967 2 0 729 730 Fragmentation avoidance in the kernel works by grouping pages of different 731 migrate types into the same contiguous regions of memory called page blocks. 732 A page block is typically the size of the default hugepage size e.g. 2MB on 733 X86-64. By keeping pages grouped based on their ability to move, the kernel 734 can reclaim pages within a page block to satisfy a high-order allocation. 735 736 The pagetypinfo begins with information on the size of a page block. It 737 then gives the same type of information as buddyinfo except broken down 738 by migrate-type and finishes with details on how many page blocks of each 739 type exist. 740 741 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 742 from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can 743 make an estimate of the likely number of huge pages that can be allocated 744 at a given point in time. All the "Movable" blocks should be allocatable 745 unless memory has been mlock()'d. Some of the Reclaimable blocks should 746 also be allocatable although a lot of filesystem metadata may have to be 747 reclaimed to achieve this. 748 749 .............................................................................. 750 751 meminfo: 752 753 Provides information about distribution and utilization of memory. This 754 varies by architecture and compile options. The following is from a 755 16GB PIII, which has highmem enabled. You may not have all of these fields. 756 757 > cat /proc/meminfo 758 759 The "Locked" indicates whether the mapping is locked in memory or not. 760 761 762 MemTotal: 16344972 kB 763 MemFree: 13634064 kB 764 Buffers: 3656 kB 765 Cached: 1195708 kB 766 SwapCached: 0 kB 767 Active: 891636 kB 768 Inactive: 1077224 kB 769 HighTotal: 15597528 kB 770 HighFree: 13629632 kB 771 LowTotal: 747444 kB 772 LowFree: 4432 kB 773 SwapTotal: 0 kB 774 SwapFree: 0 kB 775 Dirty: 968 kB 776 Writeback: 0 kB 777 AnonPages: 861800 kB 778 Mapped: 280372 kB 779 Slab: 284364 kB 780 SReclaimable: 159856 kB 781 SUnreclaim: 124508 kB 782 PageTables: 24448 kB 783 NFS_Unstable: 0 kB 784 Bounce: 0 kB 785 WritebackTmp: 0 kB 786 CommitLimit: 7669796 kB 787 Committed_AS: 100056 kB 788 VmallocTotal: 112216 kB 789 VmallocUsed: 428 kB 790 VmallocChunk: 111088 kB 791 AnonHugePages: 49152 kB 792 793 MemTotal: Total usable ram (i.e. physical ram minus a few reserved 794 bits and the kernel binary code) 795 MemFree: The sum of LowFree+HighFree 796 Buffers: Relatively temporary storage for raw disk blocks 797 shouldn't get tremendously large (20MB or so) 798 Cached: in-memory cache for files read from the disk (the 799 pagecache). Doesn't include SwapCached 800 SwapCached: Memory that once was swapped out, is swapped back in but 801 still also is in the swapfile (if memory is needed it 802 doesn't need to be swapped out AGAIN because it is already 803 in the swapfile. This saves I/O) 804 Active: Memory that has been used more recently and usually not 805 reclaimed unless absolutely necessary. 806 Inactive: Memory which has been less recently used. It is more 807 eligible to be reclaimed for other purposes 808 HighTotal: 809 HighFree: Highmem is all memory above ~860MB of physical memory 810 Highmem areas are for use by userspace programs, or 811 for the pagecache. The kernel must use tricks to access 812 this memory, making it slower to access than lowmem. 813 LowTotal: 814 LowFree: Lowmem is memory which can be used for everything that 815 highmem can be used for, but it is also available for the 816 kernel's use for its own data structures. Among many 817 other things, it is where everything from the Slab is 818 allocated. Bad things happen when you're out of lowmem. 819 SwapTotal: total amount of swap space available 820 SwapFree: Memory which has been evicted from RAM, and is temporarily 821 on the disk 822 Dirty: Memory which is waiting to get written back to the disk 823 Writeback: Memory which is actively being written back to the disk 824 AnonPages: Non-file backed pages mapped into userspace page tables 825 AnonHugePages: Non-file backed huge pages mapped into userspace page tables 826 Mapped: files which have been mmaped, such as libraries 827 Slab: in-kernel data structures cache 828 SReclaimable: Part of Slab, that might be reclaimed, such as caches 829 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure 830 PageTables: amount of memory dedicated to the lowest level of page 831 tables. 832 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable 833 storage 834 Bounce: Memory used for block device "bounce buffers" 835 WritebackTmp: Memory used by FUSE for temporary writeback buffers 836 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), 837 this is the total amount of memory currently available to 838 be allocated on the system. This limit is only adhered to 839 if strict overcommit accounting is enabled (mode 2 in 840 'vm.overcommit_memory'). 841 The CommitLimit is calculated with the following formula: 842 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap 843 For example, on a system with 1G of physical RAM and 7G 844 of swap with a `vm.overcommit_ratio` of 30 it would 845 yield a CommitLimit of 7.3G. 846 For more details, see the memory overcommit documentation 847 in vm/overcommit-accounting. 848 Committed_AS: The amount of memory presently allocated on the system. 849 The committed memory is a sum of all of the memory which 850 has been allocated by processes, even if it has not been 851 "used" by them as of yet. A process which malloc()'s 1G 852 of memory, but only touches 300M of it will only show up 853 as using 300M of memory even if it has the address space 854 allocated for the entire 1G. This 1G is memory which has 855 been "committed" to by the VM and can be used at any time 856 by the allocating application. With strict overcommit 857 enabled on the system (mode 2 in 'vm.overcommit_memory'), 858 allocations which would exceed the CommitLimit (detailed 859 above) will not be permitted. This is useful if one needs 860 to guarantee that processes will not fail due to lack of 861 memory once that memory has been successfully allocated. 862 VmallocTotal: total size of vmalloc memory area 863 VmallocUsed: amount of vmalloc area which is used 864 VmallocChunk: largest contiguous block of vmalloc area which is free 865 866 .............................................................................. 867 868 vmallocinfo: 869 870 Provides information about vmalloced/vmaped areas. One line per area, 871 containing the virtual address range of the area, size in bytes, 872 caller information of the creator, and optional information depending 873 on the kind of area : 874 875 pages=nr number of pages 876 phys=addr if a physical address was specified 877 ioremap I/O mapping (ioremap() and friends) 878 vmalloc vmalloc() area 879 vmap vmap()ed pages 880 user VM_USERMAP area 881 vpages buffer for pages pointers was vmalloced (huge area) 882 N<node>=nr (Only on NUMA kernels) 883 Number of pages allocated on memory node <node> 884 885 > cat /proc/vmallocinfo 886 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 887 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 888 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 889 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 890 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 891 phys=7fee8000 ioremap 892 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 893 phys=7fee7000 ioremap 894 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 895 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 896 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 897 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 898 pages=2 vmalloc N1=2 899 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 900 /0x130 [x_tables] pages=4 vmalloc N0=4 901 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 902 pages=14 vmalloc N2=14 903 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 904 pages=4 vmalloc N1=4 905 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 906 pages=2 vmalloc N1=2 907 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 908 pages=10 vmalloc N0=10 909 910 .............................................................................. 911 912 softirqs: 913 914 Provides counts of softirq handlers serviced since boot time, for each cpu. 915 916 > cat /proc/softirqs 917 CPU0 CPU1 CPU2 CPU3 918 HI: 0 0 0 0 919 TIMER: 27166 27120 27097 27034 920 NET_TX: 0 0 0 17 921 NET_RX: 42 0 0 39 922 BLOCK: 0 0 107 1121 923 TASKLET: 0 0 0 290 924 SCHED: 27035 26983 26971 26746 925 HRTIMER: 0 0 0 0 926 RCU: 1678 1769 2178 2250 927 928 929 1.3 IDE devices in /proc/ide 930 ---------------------------- 931 932 The subdirectory /proc/ide contains information about all IDE devices of which 933 the kernel is aware. There is one subdirectory for each IDE controller, the 934 file drivers and a link for each IDE device, pointing to the device directory 935 in the controller specific subtree. 936 937 The file drivers contains general information about the drivers used for the 938 IDE devices: 939 940 > cat /proc/ide/drivers 941 ide-cdrom version 4.53 942 ide-disk version 1.08 943 944 More detailed information can be found in the controller specific 945 subdirectories. These are named ide0, ide1 and so on. Each of these 946 directories contains the files shown in table 1-6. 947 948 949 Table 1-6: IDE controller info in /proc/ide/ide? 950 .............................................................................. 951 File Content 952 channel IDE channel (0 or 1) 953 config Configuration (only for PCI/IDE bridge) 954 mate Mate name 955 model Type/Chipset of IDE controller 956 .............................................................................. 957 958 Each device connected to a controller has a separate subdirectory in the 959 controllers directory. The files listed in table 1-7 are contained in these 960 directories. 961 962 963 Table 1-7: IDE device information 964 .............................................................................. 965 File Content 966 cache The cache 967 capacity Capacity of the medium (in 512Byte blocks) 968 driver driver and version 969 geometry physical and logical geometry 970 identify device identify block 971 media media type 972 model device identifier 973 settings device setup 974 smart_thresholds IDE disk management thresholds 975 smart_values IDE disk management values 976 .............................................................................. 977 978 The most interesting file is settings. This file contains a nice overview of 979 the drive parameters: 980 981 # cat /proc/ide/ide0/hda/settings 982 name value min max mode 983 ---- ----- --- --- ---- 984 bios_cyl 526 0 65535 rw 985 bios_head 255 0 255 rw 986 bios_sect 63 0 63 rw 987 breada_readahead 4 0 127 rw 988 bswap 0 0 1 r 989 file_readahead 72 0 2097151 rw 990 io_32bit 0 0 3 rw 991 keepsettings 0 0 1 rw 992 max_kb_per_request 122 1 127 rw 993 multcount 0 0 8 rw 994 nice1 1 0 1 rw 995 nowerr 0 0 1 rw 996 pio_mode write-only 0 255 w 997 slow 0 0 1 rw 998 unmaskirq 0 0 1 rw 999 using_dma 0 0 1 rw 1000 1001 1002 1.4 Networking info in /proc/net 1003 -------------------------------- 1004 1005 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 1006 additional values you get for IP version 6 if you configure the kernel to 1007 support this. Table 1-9 lists the files and their meaning. 1008 1009 1010 Table 1-8: IPv6 info in /proc/net 1011 .............................................................................. 1012 File Content 1013 udp6 UDP sockets (IPv6) 1014 tcp6 TCP sockets (IPv6) 1015 raw6 Raw device statistics (IPv6) 1016 igmp6 IP multicast addresses, which this host joined (IPv6) 1017 if_inet6 List of IPv6 interface addresses 1018 ipv6_route Kernel routing table for IPv6 1019 rt6_stats Global IPv6 routing tables statistics 1020 sockstat6 Socket statistics (IPv6) 1021 snmp6 Snmp data (IPv6) 1022 .............................................................................. 1023 1024 1025 Table 1-9: Network info in /proc/net 1026 .............................................................................. 1027 File Content 1028 arp Kernel ARP table 1029 dev network devices with statistics 1030 dev_mcast the Layer2 multicast groups a device is listening too 1031 (interface index, label, number of references, number of bound 1032 addresses). 1033 dev_stat network device status 1034 ip_fwchains Firewall chain linkage 1035 ip_fwnames Firewall chain names 1036 ip_masq Directory containing the masquerading tables 1037 ip_masquerade Major masquerading table 1038 netstat Network statistics 1039 raw raw device statistics 1040 route Kernel routing table 1041 rpc Directory containing rpc info 1042 rt_cache Routing cache 1043 snmp SNMP data 1044 sockstat Socket statistics 1045 tcp TCP sockets 1046 udp UDP sockets 1047 unix UNIX domain sockets 1048 wireless Wireless interface data (Wavelan etc) 1049 igmp IP multicast addresses, which this host joined 1050 psched Global packet scheduler parameters. 1051 netlink List of PF_NETLINK sockets 1052 ip_mr_vifs List of multicast virtual interfaces 1053 ip_mr_cache List of multicast routing cache 1054 .............................................................................. 1055 1056 You can use this information to see which network devices are available in 1057 your system and how much traffic was routed over those devices: 1058 1059 > cat /proc/net/dev 1060 Inter-|Receive |[... 1061 face |bytes packets errs drop fifo frame compressed multicast|[... 1062 lo: 908188 5596 0 0 0 0 0 0 [... 1063 ppp0:15475140 20721 410 0 0 410 0 0 [... 1064 eth0: 614530 7085 0 0 0 0 0 1 [... 1065 1066 ...] Transmit 1067 ...] bytes packets errs drop fifo colls carrier compressed 1068 ...] 908188 5596 0 0 0 0 0 0 1069 ...] 1375103 17405 0 0 0 0 0 0 1070 ...] 1703981 5535 0 0 0 3 0 0 1071 1072 In addition, each Channel Bond interface has its own directory. For 1073 example, the bond0 device will have a directory called /proc/net/bond0/. 1074 It will contain information that is specific to that bond, such as the 1075 current slaves of the bond, the link status of the slaves, and how 1076 many times the slaves link has failed. 1077 1078 1.5 SCSI info 1079 ------------- 1080 1081 If you have a SCSI host adapter in your system, you'll find a subdirectory 1082 named after the driver for this adapter in /proc/scsi. You'll also see a list 1083 of all recognized SCSI devices in /proc/scsi: 1084 1085 >cat /proc/scsi/scsi 1086 Attached devices: 1087 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1088 Vendor: IBM Model: DGHS09U Rev: 03E0 1089 Type: Direct-Access ANSI SCSI revision: 03 1090 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1091 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1092 Type: CD-ROM ANSI SCSI revision: 02 1093 1094 1095 The directory named after the driver has one file for each adapter found in 1096 the system. These files contain information about the controller, including 1097 the used IRQ and the IO address range. The amount of information shown is 1098 dependent on the adapter you use. The example shows the output for an Adaptec 1099 AHA-2940 SCSI adapter: 1100 1101 > cat /proc/scsi/aic7xxx/0 1102 1103 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1104 Compile Options: 1105 TCQ Enabled By Default : Disabled 1106 AIC7XXX_PROC_STATS : Disabled 1107 AIC7XXX_RESET_DELAY : 5 1108 Adapter Configuration: 1109 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1110 Ultra Wide Controller 1111 PCI MMAPed I/O Base: 0xeb001000 1112 Adapter SEEPROM Config: SEEPROM found and used. 1113 Adaptec SCSI BIOS: Enabled 1114 IRQ: 10 1115 SCBs: Active 0, Max Active 2, 1116 Allocated 15, HW 16, Page 255 1117 Interrupts: 160328 1118 BIOS Control Word: 0x18b6 1119 Adapter Control Word: 0x005b 1120 Extended Translation: Enabled 1121 Disconnect Enable Flags: 0xffff 1122 Ultra Enable Flags: 0x0001 1123 Tag Queue Enable Flags: 0x0000 1124 Ordered Queue Tag Flags: 0x0000 1125 Default Tag Queue Depth: 8 1126 Tagged Queue By Device array for aic7xxx host instance 0: 1127 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1128 Actual queue depth per device for aic7xxx host instance 0: 1129 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1130 Statistics: 1131 (scsi0:0:0:0) 1132 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1133 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1134 Total transfers 160151 (74577 reads and 85574 writes) 1135 (scsi0:0:6:0) 1136 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1137 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1138 Total transfers 0 (0 reads and 0 writes) 1139 1140 1141 1.6 Parallel port info in /proc/parport 1142 --------------------------------------- 1143 1144 The directory /proc/parport contains information about the parallel ports of 1145 your system. It has one subdirectory for each port, named after the port 1146 number (0,1,2,...). 1147 1148 These directories contain the four files shown in Table 1-10. 1149 1150 1151 Table 1-10: Files in /proc/parport 1152 .............................................................................. 1153 File Content 1154 autoprobe Any IEEE-1284 device ID information that has been acquired. 1155 devices list of the device drivers using that port. A + will appear by the 1156 name of the device currently using the port (it might not appear 1157 against any). 1158 hardware Parallel port's base address, IRQ line and DMA channel. 1159 irq IRQ that parport is using for that port. This is in a separate 1160 file to allow you to alter it by writing a new value in (IRQ 1161 number or none). 1162 .............................................................................. 1163 1164 1.7 TTY info in /proc/tty 1165 ------------------------- 1166 1167 Information about the available and actually used tty's can be found in the 1168 directory /proc/tty.You'll find entries for drivers and line disciplines in 1169 this directory, as shown in Table 1-11. 1170 1171 1172 Table 1-11: Files in /proc/tty 1173 .............................................................................. 1174 File Content 1175 drivers list of drivers and their usage 1176 ldiscs registered line disciplines 1177 driver/serial usage statistic and status of single tty lines 1178 .............................................................................. 1179 1180 To see which tty's are currently in use, you can simply look into the file 1181 /proc/tty/drivers: 1182 1183 > cat /proc/tty/drivers 1184 pty_slave /dev/pts 136 0-255 pty:slave 1185 pty_master /dev/ptm 128 0-255 pty:master 1186 pty_slave /dev/ttyp 3 0-255 pty:slave 1187 pty_master /dev/pty 2 0-255 pty:master 1188 serial /dev/cua 5 64-67 serial:callout 1189 serial /dev/ttyS 4 64-67 serial 1190 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1191 /dev/ptmx /dev/ptmx 5 2 system 1192 /dev/console /dev/console 5 1 system:console 1193 /dev/tty /dev/tty 5 0 system:/dev/tty 1194 unknown /dev/tty 4 1-63 console 1195 1196 1197 1.8 Miscellaneous kernel statistics in /proc/stat 1198 ------------------------------------------------- 1199 1200 Various pieces of information about kernel activity are available in the 1201 /proc/stat file. All of the numbers reported in this file are aggregates 1202 since the system first booted. For a quick look, simply cat the file: 1203 1204 > cat /proc/stat 1205 cpu 2255 34 2290 22625563 6290 127 456 0 0 1206 cpu0 1132 34 1441 11311718 3675 127 438 0 0 1207 cpu1 1123 0 849 11313845 2614 0 18 0 0 1208 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1209 ctxt 1990473 1210 btime 1062191376 1211 processes 2915 1212 procs_running 1 1213 procs_blocked 0 1214 softirq 183433 0 21755 12 39 1137 231 21459 2263 1215 1216 The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1217 lines. These numbers identify the amount of time the CPU has spent performing 1218 different kinds of work. Time units are in USER_HZ (typically hundredths of a 1219 second). The meanings of the columns are as follows, from left to right: 1220 1221 - user: normal processes executing in user mode 1222 - nice: niced processes executing in user mode 1223 - system: processes executing in kernel mode 1224 - idle: twiddling thumbs 1225 - iowait: waiting for I/O to complete 1226 - irq: servicing interrupts 1227 - softirq: servicing softirqs 1228 - steal: involuntary wait 1229 - guest: running a normal guest 1230 - guest_nice: running a niced guest 1231 1232 The "intr" line gives counts of interrupts serviced since boot time, for each 1233 of the possible system interrupts. The first column is the total of all 1234 interrupts serviced; each subsequent column is the total for that particular 1235 interrupt. 1236 1237 The "ctxt" line gives the total number of context switches across all CPUs. 1238 1239 The "btime" line gives the time at which the system booted, in seconds since 1240 the Unix epoch. 1241 1242 The "processes" line gives the number of processes and threads created, which 1243 includes (but is not limited to) those created by calls to the fork() and 1244 clone() system calls. 1245 1246 The "procs_running" line gives the total number of threads that are 1247 running or ready to run (i.e., the total number of runnable threads). 1248 1249 The "procs_blocked" line gives the number of processes currently blocked, 1250 waiting for I/O to complete. 1251 1252 The "softirq" line gives counts of softirqs serviced since boot time, for each 1253 of the possible system softirqs. The first column is the total of all 1254 softirqs serviced; each subsequent column is the total for that particular 1255 softirq. 1256 1257 1258 1.9 Ext4 file system parameters 1259 ------------------------------ 1260 1261 Information about mounted ext4 file systems can be found in 1262 /proc/fs/ext4. Each mounted filesystem will have a directory in 1263 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1264 /proc/fs/ext4/dm-0). The files in each per-device directory are shown 1265 in Table 1-12, below. 1266 1267 Table 1-12: Files in /proc/fs/ext4/<devname> 1268 .............................................................................. 1269 File Content 1270 mb_groups details of multiblock allocator buddy cache of free blocks 1271 .............................................................................. 1272 1273 2.0 /proc/consoles 1274 ------------------ 1275 Shows registered system console lines. 1276 1277 To see which character device lines are currently used for the system console 1278 /dev/console, you may simply look into the file /proc/consoles: 1279 1280 > cat /proc/consoles 1281 tty0 -WU (ECp) 4:7 1282 ttyS0 -W- (Ep) 4:64 1283 1284 The columns are: 1285 1286 device name of the device 1287 operations R = can do read operations 1288 W = can do write operations 1289 U = can do unblank 1290 flags E = it is enabled 1291 C = it is preferred console 1292 B = it is primary boot console 1293 p = it is used for printk buffer 1294 b = it is not a TTY but a Braille device 1295 a = it is safe to use when cpu is offline 1296 major:minor major and minor number of the device separated by a colon 1297 1298 ------------------------------------------------------------------------------ 1299 Summary 1300 ------------------------------------------------------------------------------ 1301 The /proc file system serves information about the running system. It not only 1302 allows access to process data but also allows you to request the kernel status 1303 by reading files in the hierarchy. 1304 1305 The directory structure of /proc reflects the types of information and makes 1306 it easy, if not obvious, where to look for specific data. 1307 ------------------------------------------------------------------------------ 1308 1309 ------------------------------------------------------------------------------ 1310 CHAPTER 2: MODIFYING SYSTEM PARAMETERS 1311 ------------------------------------------------------------------------------ 1312 1313 ------------------------------------------------------------------------------ 1314 In This Chapter 1315 ------------------------------------------------------------------------------ 1316 * Modifying kernel parameters by writing into files found in /proc/sys 1317 * Exploring the files which modify certain parameters 1318 * Review of the /proc/sys file tree 1319 ------------------------------------------------------------------------------ 1320 1321 1322 A very interesting part of /proc is the directory /proc/sys. This is not only 1323 a source of information, it also allows you to change parameters within the 1324 kernel. Be very careful when attempting this. You can optimize your system, 1325 but you can also cause it to crash. Never alter kernel parameters on a 1326 production system. Set up a development machine and test to make sure that 1327 everything works the way you want it to. You may have no alternative but to 1328 reboot the machine once an error has been made. 1329 1330 To change a value, simply echo the new value into the file. An example is 1331 given below in the section on the file system data. You need to be root to do 1332 this. You can create your own boot script to perform this every time your 1333 system boots. 1334 1335 The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1336 general things in the operation of the Linux kernel. Since some of the files 1337 can inadvertently disrupt your system, it is advisable to read both 1338 documentation and source before actually making adjustments. In any case, be 1339 very careful when writing to any of these files. The entries in /proc may 1340 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1341 review the kernel documentation in the directory /usr/src/linux/Documentation. 1342 This chapter is heavily based on the documentation included in the pre 2.2 1343 kernels, and became part of it in version 2.2.1 of the Linux kernel. 1344 1345 Please see: Documentation/sysctl/ directory for descriptions of these 1346 entries. 1347 1348 ------------------------------------------------------------------------------ 1349 Summary 1350 ------------------------------------------------------------------------------ 1351 Certain aspects of kernel behavior can be modified at runtime, without the 1352 need to recompile the kernel, or even to reboot the system. The files in the 1353 /proc/sys tree can not only be read, but also modified. You can use the echo 1354 command to write value into these files, thereby changing the default settings 1355 of the kernel. 1356 ------------------------------------------------------------------------------ 1357 1358 ------------------------------------------------------------------------------ 1359 CHAPTER 3: PER-PROCESS PARAMETERS 1360 ------------------------------------------------------------------------------ 1361 1362 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1363 -------------------------------------------------------------------------------- 1364 1365 These file can be used to adjust the badness heuristic used to select which 1366 process gets killed in out of memory conditions. 1367 1368 The badness heuristic assigns a value to each candidate task ranging from 0 1369 (never kill) to 1000 (always kill) to determine which process is targeted. The 1370 units are roughly a proportion along that range of allowed memory the process 1371 may allocate from based on an estimation of its current memory and swap use. 1372 For example, if a task is using all allowed memory, its badness score will be 1373 1000. If it is using half of its allowed memory, its score will be 500. 1374 1375 There is an additional factor included in the badness score: root 1376 processes are given 3% extra memory over other tasks. 1377 1378 The amount of "allowed" memory depends on the context in which the oom killer 1379 was called. If it is due to the memory assigned to the allocating task's cpuset 1380 being exhausted, the allowed memory represents the set of mems assigned to that 1381 cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1382 memory represents the set of mempolicy nodes. If it is due to a memory 1383 limit (or swap limit) being reached, the allowed memory is that configured 1384 limit. Finally, if it is due to the entire system being out of memory, the 1385 allowed memory represents all allocatable resources. 1386 1387 The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1388 is used to determine which task to kill. Acceptable values range from -1000 1389 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1390 polarize the preference for oom killing either by always preferring a certain 1391 task or completely disabling it. The lowest possible value, -1000, is 1392 equivalent to disabling oom killing entirely for that task since it will always 1393 report a badness score of 0. 1394 1395 Consequently, it is very simple for userspace to define the amount of memory to 1396 consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1397 example, is roughly equivalent to allowing the remainder of tasks sharing the 1398 same system, cpuset, mempolicy, or memory controller resources to use at least 1399 50% more memory. A value of -500, on the other hand, would be roughly 1400 equivalent to discounting 50% of the task's allowed memory from being considered 1401 as scoring against the task. 1402 1403 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1404 be used to tune the badness score. Its acceptable values range from -16 1405 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1406 (OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1407 scaled linearly with /proc/<pid>/oom_score_adj. 1408 1409 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1410 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1411 requires CAP_SYS_RESOURCE. 1412 1413 Caveat: when a parent task is selected, the oom killer will sacrifice any first 1414 generation children with separate address spaces instead, if possible. This 1415 avoids servers and important system daemons from being killed and loses the 1416 minimal amount of work. 1417 1418 1419 3.2 /proc/<pid>/oom_score - Display current oom-killer score 1420 ------------------------------------------------------------- 1421 1422 This file can be used to check the current score used by the oom-killer is for 1423 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1424 process should be killed in an out-of-memory situation. 1425 1426 1427 3.3 /proc/<pid>/io - Display the IO accounting fields 1428 ------------------------------------------------------- 1429 1430 This file contains IO statistics for each running process 1431 1432 Example 1433 ------- 1434 1435 test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1436 [1] 3828 1437 1438 test:/tmp # cat /proc/3828/io 1439 rchar: 323934931 1440 wchar: 323929600 1441 syscr: 632687 1442 syscw: 632675 1443 read_bytes: 0 1444 write_bytes: 323932160 1445 cancelled_write_bytes: 0 1446 1447 1448 Description 1449 ----------- 1450 1451 rchar 1452 ----- 1453 1454 I/O counter: chars read 1455 The number of bytes which this task has caused to be read from storage. This 1456 is simply the sum of bytes which this process passed to read() and pread(). 1457 It includes things like tty IO and it is unaffected by whether or not actual 1458 physical disk IO was required (the read might have been satisfied from 1459 pagecache) 1460 1461 1462 wchar 1463 ----- 1464 1465 I/O counter: chars written 1466 The number of bytes which this task has caused, or shall cause to be written 1467 to disk. Similar caveats apply here as with rchar. 1468 1469 1470 syscr 1471 ----- 1472 1473 I/O counter: read syscalls 1474 Attempt to count the number of read I/O operations, i.e. syscalls like read() 1475 and pread(). 1476 1477 1478 syscw 1479 ----- 1480 1481 I/O counter: write syscalls 1482 Attempt to count the number of write I/O operations, i.e. syscalls like 1483 write() and pwrite(). 1484 1485 1486 read_bytes 1487 ---------- 1488 1489 I/O counter: bytes read 1490 Attempt to count the number of bytes which this process really did cause to 1491 be fetched from the storage layer. Done at the submit_bio() level, so it is 1492 accurate for block-backed filesystems. <please add status regarding NFS and 1493 CIFS at a later time> 1494 1495 1496 write_bytes 1497 ----------- 1498 1499 I/O counter: bytes written 1500 Attempt to count the number of bytes which this process caused to be sent to 1501 the storage layer. This is done at page-dirtying time. 1502 1503 1504 cancelled_write_bytes 1505 --------------------- 1506 1507 The big inaccuracy here is truncate. If a process writes 1MB to a file and 1508 then deletes the file, it will in fact perform no writeout. But it will have 1509 been accounted as having caused 1MB of write. 1510 In other words: The number of bytes which this process caused to not happen, 1511 by truncating pagecache. A task can cause "negative" IO too. If this task 1512 truncates some dirty pagecache, some IO which another task has been accounted 1513 for (in its write_bytes) will not be happening. We _could_ just subtract that 1514 from the truncating task's write_bytes, but there is information loss in doing 1515 that. 1516 1517 1518 Note 1519 ---- 1520 1521 At its current implementation state, this is a bit racy on 32-bit machines: if 1522 process A reads process B's /proc/pid/io while process B is updating one of 1523 those 64-bit counters, process A could see an intermediate result. 1524 1525 1526 More information about this can be found within the taskstats documentation in 1527 Documentation/accounting. 1528 1529 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1530 --------------------------------------------------------------- 1531 When a process is dumped, all anonymous memory is written to a core file as 1532 long as the size of the core file isn't limited. But sometimes we don't want 1533 to dump some memory segments, for example, huge shared memory. Conversely, 1534 sometimes we want to save file-backed memory segments into a core file, not 1535 only the individual files. 1536 1537 /proc/<pid>/coredump_filter allows you to customize which memory segments 1538 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1539 of memory types. If a bit of the bitmask is set, memory segments of the 1540 corresponding memory type are dumped, otherwise they are not dumped. 1541 1542 The following 7 memory types are supported: 1543 - (bit 0) anonymous private memory 1544 - (bit 1) anonymous shared memory 1545 - (bit 2) file-backed private memory 1546 - (bit 3) file-backed shared memory 1547 - (bit 4) ELF header pages in file-backed private memory areas (it is 1548 effective only if the bit 2 is cleared) 1549 - (bit 5) hugetlb private memory 1550 - (bit 6) hugetlb shared memory 1551 1552 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1553 are always dumped regardless of the bitmask status. 1554 1555 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only 1556 effected by bit 5-6. 1557 1558 Default value of coredump_filter is 0x23; this means all anonymous memory 1559 segments and hugetlb private memory are dumped. 1560 1561 If you don't want to dump all shared memory segments attached to pid 1234, 1562 write 0x21 to the process's proc file. 1563 1564 $ echo 0x21 > /proc/1234/coredump_filter 1565 1566 When a new process is created, the process inherits the bitmask status from its 1567 parent. It is useful to set up coredump_filter before the program runs. 1568 For example: 1569 1570 $ echo 0x7 > /proc/self/coredump_filter 1571 $ ./some_program 1572 1573 3.5 /proc/<pid>/mountinfo - Information about mounts 1574 -------------------------------------------------------- 1575 1576 This file contains lines of the form: 1577 1578 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1579 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1580 1581 (1) mount ID: unique identifier of the mount (may be reused after umount) 1582 (2) parent ID: ID of parent (or of self for the top of the mount tree) 1583 (3) major:minor: value of st_dev for files on filesystem 1584 (4) root: root of the mount within the filesystem 1585 (5) mount point: mount point relative to the process's root 1586 (6) mount options: per mount options 1587 (7) optional fields: zero or more fields of the form "tag[:value]" 1588 (8) separator: marks the end of the optional fields 1589 (9) filesystem type: name of filesystem of the form "type[.subtype]" 1590 (10) mount source: filesystem specific information or "none" 1591 (11) super options: per super block options 1592 1593 Parsers should ignore all unrecognised optional fields. Currently the 1594 possible optional fields are: 1595 1596 shared:X mount is shared in peer group X 1597 master:X mount is slave to peer group X 1598 propagate_from:X mount is slave and receives propagation from peer group X (*) 1599 unbindable mount is unbindable 1600 1601 (*) X is the closest dominant peer group under the process's root. If 1602 X is the immediate master of the mount, or if there's no dominant peer 1603 group under the same root, then only the "master:X" field is present 1604 and not the "propagate_from:X" field. 1605 1606 For more information on mount propagation see: 1607 1608 Documentation/filesystems/sharedsubtree.txt 1609 1610 1611 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1612 -------------------------------------------------------- 1613 These files provide a method to access a tasks comm value. It also allows for 1614 a task to set its own or one of its thread siblings comm value. The comm value 1615 is limited in size compared to the cmdline value, so writing anything longer 1616 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1617 comm value. 1618 1619 1620 3.7 /proc/<pid>/task/<tid>/children - Information about task children 1621 ------------------------------------------------------------------------- 1622 This file provides a fast way to retrieve first level children pids 1623 of a task pointed by <pid>/<tid> pair. The format is a space separated 1624 stream of pids. 1625 1626 Note the "first level" here -- if a child has own children they will 1627 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children 1628 to obtain the descendants. 1629 1630 Since this interface is intended to be fast and cheap it doesn't 1631 guarantee to provide precise results and some children might be 1632 skipped, especially if they've exited right after we printed their 1633 pids, so one need to either stop or freeze processes being inspected 1634 if precise results are needed. 1635 1636 1637 3.7 /proc/<pid>/fdinfo/<fd> - Information about opened file 1638 --------------------------------------------------------------- 1639 This file provides information associated with an opened file. The regular 1640 files have at least two fields -- 'pos' and 'flags'. The 'pos' represents 1641 the current offset of the opened file in decimal form [see lseek(2) for 1642 details] and 'flags' denotes the octal O_xxx mask the file has been 1643 created with [see open(2) for details]. 1644 1645 A typical output is 1646 1647 pos: 0 1648 flags: 0100002 1649 1650 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags 1651 pair provide additional information particular to the objects they represent. 1652 1653 Eventfd files 1654 ~~~~~~~~~~~~~ 1655 pos: 0 1656 flags: 04002 1657 eventfd-count: 5a 1658 1659 where 'eventfd-count' is hex value of a counter. 1660 1661 Signalfd files 1662 ~~~~~~~~~~~~~~ 1663 pos: 0 1664 flags: 04002 1665 sigmask: 0000000000000200 1666 1667 where 'sigmask' is hex value of the signal mask associated 1668 with a file. 1669 1670 Epoll files 1671 ~~~~~~~~~~~ 1672 pos: 0 1673 flags: 02 1674 tfd: 5 events: 1d data: ffffffffffffffff 1675 1676 where 'tfd' is a target file descriptor number in decimal form, 1677 'events' is events mask being watched and the 'data' is data 1678 associated with a target [see epoll(7) for more details]. 1679 1680 Fsnotify files 1681 ~~~~~~~~~~~~~~ 1682 For inotify files the format is the following 1683 1684 pos: 0 1685 flags: 02000000 1686 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d 1687 1688 where 'wd' is a watch descriptor in decimal form, ie a target file 1689 descriptor number, 'ino' and 'sdev' are inode and device where the 1690 target file resides and the 'mask' is the mask of events, all in hex 1691 form [see inotify(7) for more details]. 1692 1693 If the kernel was built with exportfs support, the path to the target 1694 file is encoded as a file handle. The file handle is provided by three 1695 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex 1696 format. 1697 1698 If the kernel is built without exportfs support the file handle won't be 1699 printed out. 1700 1701 If there is no inotify mark attached yet the 'inotify' line will be omitted. 1702 1703 For fanotify files the format is 1704 1705 pos: 0 1706 flags: 02 1707 fanotify flags:10 event-flags:0 1708 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 1709 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 1710 1711 where fanotify 'flags' and 'event-flags' are values used in fanotify_init 1712 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of 1713 flags associated with mark which are tracked separately from events 1714 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events 1715 mask and 'ignored_mask' is the mask of events which are to be ignored. 1716 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' 1717 does provide information about flags and mask used in fanotify_mark 1718 call [see fsnotify manpage for details]. 1719 1720 While the first three lines are mandatory and always printed, the rest is 1721 optional and may be omitted if no marks created yet. 1722 1723 1724 ------------------------------------------------------------------------------ 1725 Configuring procfs 1726 ------------------------------------------------------------------------------ 1727 1728 4.1 Mount options 1729 --------------------- 1730 1731 The following mount options are supported: 1732 1733 hidepid= Set /proc/<pid>/ access mode. 1734 gid= Set the group authorized to learn processes information. 1735 1736 hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories 1737 (default). 1738 1739 hidepid=1 means users may not access any /proc/<pid>/ directories but their 1740 own. Sensitive files like cmdline, sched*, status are now protected against 1741 other users. This makes it impossible to learn whether any user runs 1742 specific program (given the program doesn't reveal itself by its behaviour). 1743 As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users, 1744 poorly written programs passing sensitive information via program arguments are 1745 now protected against local eavesdroppers. 1746 1747 hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other 1748 users. It doesn't mean that it hides a fact whether a process with a specific 1749 pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), 1750 but it hides process' uid and gid, which may be learned by stat()'ing 1751 /proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering 1752 information about running processes, whether some daemon runs with elevated 1753 privileges, whether other user runs some sensitive program, whether other users 1754 run any program at all, etc. 1755 1756 gid= defines a group authorized to learn processes information otherwise 1757 prohibited by hidepid=. If you use some daemon like identd which needs to learn 1758 information about processes information, just add identd to this group.
- [ filesystems ]
- 00-INDEX
- 9p.txt
- adfs.txt
- affs.txt
- afs.txt
- autofs4-mount-control.txt
- automount-support.txt
- befs.txt
- bfs.txt
- btrfs.txt
- [ caching ]
- ceph.txt
- cifs.txt
- coda.txt
- [ configfs ]
- cramfs.txt
- debugfs.txt
- devpts.txt
- directory-locking
- dlmfs.txt
- dnotify.txt
- dnotify_test.c
- ecryptfs.txt
- efivarfs.txt
- exofs.txt
- ext2.txt
- ext3.txt
- ext4.txt
- f2fs.txt
- fiemap.txt
- files.txt
- fuse.txt
- gfs2-glocks.txt
- gfs2-uevents.txt
- gfs2.txt
- hfs.txt
- hfsplus.txt
- hpfs.txt
- inotify.txt
- isofs.txt
- jfs.txt
- Locking
- locks.txt
- logfs.txt
- Makefile
- mandatory-locking.txt
- ncpfs.txt
- [ nfs ]
- nilfs2.txt
- ntfs.txt
- ocfs2.txt
- omfs.txt
- path-lookup.txt
- [ pohmelfs ]
- porting
- proc.txt
- qnx6.txt
- quota.txt
- ramfs-rootfs-initramfs.txt
- relay.txt
- romfs.txt
- seq_file.txt
- sharedsubtree.txt
- spufs.txt
- squashfs.txt
- sysfs-pci.txt
- sysfs-tagging.txt
- sysfs.txt
- sysv-fs.txt
- tmpfs.txt
- ubifs.txt
- udf.txt
- ufs.txt
- vfat.txt
- vfs.txt
- xfs-delayed-logging-design.txt
- xfs.txt
- xip.txt
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