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diff --git a/Documentation/btrfs-check.8 b/Documentation/btrfs-check.8 new file mode 100644 index 00000000..da562a57 --- /dev/null +++ b/Documentation/btrfs-check.8 @@ -0,0 +1,230 @@ +'\" t +.\" Title: btrfs-check +.\" Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author] +.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/> +.\" Date: 12/05/2018 +.\" Manual: Btrfs Manual +.\" Source: Btrfs v4.19.1 +.\" Language: English +.\" +.TH "BTRFS\-CHECK" "8" "12/05/2018" "Btrfs v4\&.19\&.1" "Btrfs Manual" +.\" ----------------------------------------------------------------- +.\" * Define some portability stuff +.\" ----------------------------------------------------------------- +.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.\" http://bugs.debian.org/507673 +.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html +.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.ie \n(.g .ds Aq \(aq +.el .ds Aq ' +.\" ----------------------------------------------------------------- +.\" * set default formatting +.\" ----------------------------------------------------------------- +.\" disable hyphenation +.nh +.\" disable justification (adjust text to left margin only) +.ad l +.\" ----------------------------------------------------------------- +.\" * MAIN CONTENT STARTS HERE * +.\" ----------------------------------------------------------------- +.SH "NAME" +btrfs-check \- check or repair a btrfs filesystem +.SH "SYNOPSIS" +.sp +\fBbtrfs check\fR [options] \fI<device>\fR +.SH "DESCRIPTION" +.sp +The filesystem checker is used to verify structural integrity of a filesystem and attempt to repair it if requested\&. It is recommended to unmount the filesystem prior to running the check, but it is possible to start checking a mounted filesystem (see \fI\-\-force\fR)\&. +.sp +By default, \fBbtrfs check\fR will not modify the device but you can reaffirm that by the option \fI\-\-readonly\fR\&. +.sp +\fBbtrfsck\fR is an alias of \fBbtrfs check\fR command and is now deprecated\&. +.if n \{\ +.sp +.\} +.RS 4 +.it 1 an-trap +.nr an-no-space-flag 1 +.nr an-break-flag 1 +.br +.ps +1 +\fBWarning\fR +.ps -1 +.br +.sp +Do not use \fI\-\-repair\fR unless you are advised to do so by a developer or an experienced user, and then only after having accepted that no \fIfsck\fR successfully repair all types of filesystem corruption\&. Eg\&. some other software or hardware bugs can fatally damage a volume\&. +.sp .5v +.RE +.sp +The structural integrity check verifies if internal filesystem objects or data structures satisfy the constraints, point to the right objects or are correctly connected together\&. +.sp +There are several cross checks that can detect wrong reference counts of shared extents, backreferences, missing extents of inodes, directory and inode connectivity etc\&. +.sp +The amount of memory required can be high, depending on the size of the filesystem, similarly the run time\&. +.SH "SAFE OR ADVISORY OPTIONS" +.PP +\-b|\-\-backup +.RS 4 +use the first valid set of backup roots stored in the superblock +.sp +This can be combined with +\fI\-\-super\fR +if some of the superblocks are damaged\&. +.RE +.PP +\-\-check\-data\-csum +.RS 4 +verify checksums of data blocks +.sp +This expects that the filesystem is otherwise OK, and is basically and offline +\fIscrub\fR +but does not repair data from spare copies\&. +.RE +.PP +\-\-chunk\-root \fI<bytenr>\fR +.RS 4 +use the given offset +\fIbytenr\fR +for the chunk tree root +.RE +.PP +\-E|\-\-subvol\-extents \fI<subvolid>\fR +.RS 4 +show extent state for the given subvolume +.RE +.PP +\-p|\-\-progress +.RS 4 +indicate progress at various checking phases +.RE +.PP +\-Q|\-\-qgroup\-report +.RS 4 +verify qgroup accounting and compare against filesystem accounting +.RE +.PP +\-r|\-\-tree\-root \fI<bytenr>\fR +.RS 4 +use the given offset +\fIbytenr\fR +for the tree root +.RE +.PP +\-\-readonly +.RS 4 +(default) run in read\-only mode, this option exists to calm potential panic when users are going to run the checker +.RE +.PP +\-s|\-\-super \fI<superblock>\fR +.RS 4 +use \*(Aqsuperblock\(cqth superblock copy, valid values are 0, 1 or 2 if the respective superblock offset is within the device size +.sp +This can be used to use a different starting point if some of the primary superblock is damaged\&. +.RE +.PP +\-\-clear\-space\-cache v1|v2 +.RS 4 +completely wipe all free space cache of given type +.sp +For free space cache +\fIv1\fR, the +\fIclear_cache\fR +kernel mount option only rebuilds the free space cache for block groups that are modified while the filesystem is mounted with that option\&. Thus, using this option with +\fIv1\fR +makes it possible to actually clear the entire free space cache\&. +.sp +For free space cache +\fIv2\fR, the +\fIclear_cache\fR +kernel mount option destroys the entire free space cache\&. This option, with +\fIv2\fR +provides an alternative method of clearing the free space cache that doesn\(cqt require mounting the filesystem\&. +.RE +.SH "DANGEROUS OPTIONS" +.PP +\-\-repair +.RS 4 +enable the repair mode and attempt to fix problems where possible +.RE +.PP +\-\-init\-csum\-tree +.RS 4 +create a new checksum tree and recalculate checksums in all files +.if n \{\ +.sp +.\} +.RS 4 +.it 1 an-trap +.nr an-no-space-flag 1 +.nr an-break-flag 1 +.br +.ps +1 +\fBNote\fR +.ps -1 +.br +Do not blindly use this option to fix checksum mismatch problems\&. +.sp .5v +.RE +.RE +.PP +\-\-init\-extent\-tree +.RS 4 +build the extent tree from scratch +.if n \{\ +.sp +.\} +.RS 4 +.it 1 an-trap +.nr an-no-space-flag 1 +.nr an-break-flag 1 +.br +.ps +1 +\fBNote\fR +.ps -1 +.br +Do not use unless you know what you\(cqre doing\&. +.sp .5v +.RE +.RE +.PP +\-\-mode=MODE +.RS 4 +select mode of operation regarding memory and IO +.sp +The +\fIMODE\fR +can be one of +\fIoriginal\fR +and +\fIlowmem\fR\&. The original mode is mostly unoptimized regarding memory consumption and can lead to out\-of\-memory conditions on large filesystems\&. The possible workaround is to export the block device over network to a machine with enough memory\&. The low memory mode is supposed to address the memory consumption, at the cost of increased IO when it needs to re\-read blocks when needed\&. This may increase run time\&. +.RE +.if n \{\ +.sp +.\} +.RS 4 +.it 1 an-trap +.nr an-no-space-flag 1 +.nr an-break-flag 1 +.br +.ps +1 +\fBNote\fR +.ps -1 +.br +.sp +\fIlowmem\fR mode does not work with \fI\-\-repair\fR yet, and is still considered experimental\&. +.sp .5v +.RE +.PP +\-\-force +.RS 4 +allow work on a mounted filesystem\&. Note that this should work fine on a quiescent or read\-only mounted filesystem but may crash if the device is changed externally, eg\&. by the kernel module\&. Repair without mount checks is not supported right now\&. +.RE +.SH "EXIT STATUS" +.sp +\fBbtrfs check\fR returns a zero exit status if it succeeds\&. Non zero is returned in case of failure\&. +.SH "AVAILABILITY" +.sp +\fBbtrfs\fR is part of btrfs\-progs\&. Please refer to the btrfs wiki \m[blue]\fBhttp://btrfs\&.wiki\&.kernel\&.org\fR\m[] for further details\&. +.SH "SEE ALSO" +.sp +\fBmkfs\&.btrfs\fR(8), \fBbtrfs\-scrub\fR(8), \fBbtrfs\-rescue\fR(8) |