Based on kernel version 2.6.26. Page generated on 2008-07-16 21:13 EST.
1 Documentation for /proc/sys/fs/* kernel version 2.2.10 2 (c) 1998, 1999, Rik van Riel <riel[AT]nl.linux[DOT]org> 3 4 For general info and legal blurb, please look in README. 5 6 ============================================================== 7 8 This file contains documentation for the sysctl files in 9 /proc/sys/fs/ and is valid for Linux kernel version 2.2. 10 11 The files in this directory can be used to tune and monitor 12 miscellaneous and general things in the operation of the Linux 13 kernel. Since some of the files _can_ be used to screw up your 14 system, it is advisable to read both documentation and source 15 before actually making adjustments. 16 17 Currently, these files are in /proc/sys/fs: 18 - dentry-state 19 - dquot-max 20 - dquot-nr 21 - file-max 22 - file-nr 23 - inode-max 24 - inode-nr 25 - inode-state 26 - nr_open 27 - overflowuid 28 - overflowgid 29 - suid_dumpable 30 - super-max 31 - super-nr 32 33 Documentation for the files in /proc/sys/fs/binfmt_misc is 34 in Documentation/binfmt_misc.txt. 35 36 ============================================================== 37 38 dentry-state: 39 40 From linux/fs/dentry.c: 41 -------------------------------------------------------------- 42 struct { 43 int nr_dentry; 44 int nr_unused; 45 int age_limit; /* age in seconds */ 46 int want_pages; /* pages requested by system */ 47 int dummy[2]; 48 } dentry_stat = {0, 0, 45, 0,}; 49 -------------------------------------------------------------- 50 51 Dentries are dynamically allocated and deallocated, and 52 nr_dentry seems to be 0 all the time. Hence it's safe to 53 assume that only nr_unused, age_limit and want_pages are 54 used. Nr_unused seems to be exactly what its name says. 55 Age_limit is the age in seconds after which dcache entries 56 can be reclaimed when memory is short and want_pages is 57 nonzero when shrink_dcache_pages() has been called and the 58 dcache isn't pruned yet. 59 60 ============================================================== 61 62 dquot-max & dquot-nr: 63 64 The file dquot-max shows the maximum number of cached disk 65 quota entries. 66 67 The file dquot-nr shows the number of allocated disk quota 68 entries and the number of free disk quota entries. 69 70 If the number of free cached disk quotas is very low and 71 you have some awesome number of simultaneous system users, 72 you might want to raise the limit. 73 74 ============================================================== 75 76 file-max & file-nr: 77 78 The kernel allocates file handles dynamically, but as yet it 79 doesn't free them again. 80 81 The value in file-max denotes the maximum number of file- 82 handles that the Linux kernel will allocate. When you get lots 83 of error messages about running out of file handles, you might 84 want to increase this limit. 85 86 The three values in file-nr denote the number of allocated 87 file handles, the number of unused file handles and the maximum 88 number of file handles. When the allocated file handles come 89 close to the maximum, but the number of unused file handles is 90 significantly greater than 0, you've encountered a peak in your 91 usage of file handles and you don't need to increase the maximum. 92 93 ============================================================== 94 95 nr_open: 96 97 This denotes the maximum number of file-handles a process can 98 allocate. Default value is 1024*1024 (1048576) which should be 99 enough for most machines. Actual limit depends on RLIMIT_NOFILE 100 resource limit. 101 102 ============================================================== 103 104 inode-max, inode-nr & inode-state: 105 106 As with file handles, the kernel allocates the inode structures 107 dynamically, but can't free them yet. 108 109 The value in inode-max denotes the maximum number of inode 110 handlers. This value should be 3-4 times larger than the value 111 in file-max, since stdin, stdout and network sockets also 112 need an inode struct to handle them. When you regularly run 113 out of inodes, you need to increase this value. 114 115 The file inode-nr contains the first two items from 116 inode-state, so we'll skip to that file... 117 118 Inode-state contains three actual numbers and four dummies. 119 The actual numbers are, in order of appearance, nr_inodes, 120 nr_free_inodes and preshrink. 121 122 Nr_inodes stands for the number of inodes the system has 123 allocated, this can be slightly more than inode-max because 124 Linux allocates them one pageful at a time. 125 126 Nr_free_inodes represents the number of free inodes (?) and 127 preshrink is nonzero when the nr_inodes > inode-max and the 128 system needs to prune the inode list instead of allocating 129 more. 130 131 ============================================================== 132 133 overflowgid & overflowuid: 134 135 Some filesystems only support 16-bit UIDs and GIDs, although in Linux 136 UIDs and GIDs are 32 bits. When one of these filesystems is mounted 137 with writes enabled, any UID or GID that would exceed 65535 is translated 138 to a fixed value before being written to disk. 139 140 These sysctls allow you to change the value of the fixed UID and GID. 141 The default is 65534. 142 143 ============================================================== 144 145 suid_dumpable: 146 147 This value can be used to query and set the core dump mode for setuid 148 or otherwise protected/tainted binaries. The modes are 149 150 0 - (default) - traditional behaviour. Any process which has changed 151 privilege levels or is execute only will not be dumped 152 1 - (debug) - all processes dump core when possible. The core dump is 153 owned by the current user and no security is applied. This is 154 intended for system debugging situations only. Ptrace is unchecked. 155 2 - (suidsafe) - any binary which normally would not be dumped is dumped 156 readable by root only. This allows the end user to remove 157 such a dump but not access it directly. For security reasons 158 core dumps in this mode will not overwrite one another or 159 other files. This mode is appropriate when administrators are 160 attempting to debug problems in a normal environment. 161 162 ============================================================== 163 164 super-max & super-nr: 165 166 These numbers control the maximum number of superblocks, and 167 thus the maximum number of mounted filesystems the kernel 168 can have. You only need to increase super-max if you need to 169 mount more filesystems than the current value in super-max 170 allows you to. 171 172 ============================================================== 173 174 aio-nr & aio-max-nr: 175 176 aio-nr shows the current system-wide number of asynchronous io 177 requests. aio-max-nr allows you to change the maximum value 178 aio-nr can grow to. 179 180 ==============================================================