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authorMauro Carvalho Chehab <mchehab+huawei@kernel.org>2020-02-17 19:12:00 +0300
committerJonathan Corbet <corbet@lwn.net>2020-03-03 00:02:57 +0300
commit06dedb45b79c6550b878244879f33b6e614126bd (patch)
tree18df0ac64137c6f91887551880321774598e91f3 /Documentation/filesystems/efivarfs.rst
parentb02a17cb8ae23479c9bf306e96d2dd71422de63f (diff)
downloadlinux-06dedb45b79c6550b878244879f33b6e614126bd.tar.xz
docs: filesystems: convert efivarfs.txt to ReST
Trivial changes: - Add a SPDX header; - Adjust document title; - Mark a literal block as such; - Add it to filesystems/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/215691d747055c4ccb038ec7d78d8d1fe87fe2c0.1581955849.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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+.. 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.