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Diffstat (limited to 'Documentation/filesystems/efivarfs.rst')
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diff --git a/Documentation/filesystems/efivarfs.rst b/Documentation/filesystems/efivarfs.rst new file mode 100644 index 000000000000..90ac65683e7e --- /dev/null +++ b/Documentation/filesystems/efivarfs.rst @@ -0,0 +1,26 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================================= +efivarfs - a (U)EFI variable filesystem +======================================= + +The efivarfs filesystem was created to address the shortcomings of +using entries in sysfs to maintain EFI variables. The old sysfs EFI +variables code only supported variables of up to 1024 bytes. This +limitation existed in version 0.99 of the EFI specification, but was +removed before any full releases. Since variables can now be larger +than a single page, sysfs isn't the best interface for this. + +Variables can be created, deleted and modified with the efivarfs +filesystem. + +efivarfs is typically mounted like this:: + + mount -t efivarfs none /sys/firmware/efi/efivars + +Due to the presence of numerous firmware bugs where removing non-standard +UEFI variables causes the system firmware to fail to POST, efivarfs +files that are not well-known standardized variables are created +as immutable files. This doesn't prevent removal - "chattr -i" will work - +but it does prevent this kind of failure from being accomplished +accidentally. |