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Documentation / filesystems / efivarfs.txt




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Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.

1	
2	efivarfs - a (U)EFI variable filesystem
3	
4	The efivarfs filesystem was created to address the shortcomings of
5	using entries in sysfs to maintain EFI variables. The old sysfs EFI
6	variables code only supported variables of up to 1024 bytes. This
7	limitation existed in version 0.99 of the EFI specification, but was
8	removed before any full releases. Since variables can now be larger
9	than a single page, sysfs isn't the best interface for this.
10	
11	Variables can be created, deleted and modified with the efivarfs
12	filesystem.
13	
14	efivarfs is typically mounted like this,
15	
16		mount -t efivarfs none /sys/firmware/efi/efivars
17	
18	Due to the presence of numerous firmware bugs where removing non-standard
19	UEFI variables causes the system firmware to fail to POST, efivarfs
20	files that are not well-known standardized variables are created
21	as immutable files.  This doesn't prevent removal - "chattr -i" will work -
22	but it does prevent this kind of failure from being accomplished
23	accidentally.
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