mount: add btrfs to mount.8
Based on Documentation/filesystems/btrfs.txt Signed-off-by: Gui Hecheng <guihc.fnst@cn.fujitsu.com>
This commit is contained in:
Gui Hecheng
Karel Zak
parent
ee312c654b
commit
f36de15e2f
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@ -671,6 +671,7 @@ currently supported include:
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.IR adfs ,
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.IR affs ,
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.IR autofs ,
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.IR btrfs ,
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.IR cifs ,
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.IR coda ,
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.IR coherent ,
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@ -1245,6 +1246,191 @@ Give blocksize. Allowed values are 512, 1024, 2048, 4096.
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These options are accepted but ignored.
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(However, quota utilities may react to such strings in
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.IR /etc/fstab .)
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.SH "Mount options for btrfs"
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Btrfs is a copy on write filesystem for Linux aimed at
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implementing advanced features while focusing on fault tolerance,
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repair and easy administration.
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.TP
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.BI alloc_start= bytes
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Debugging option to force all block allocations above a certain
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byte threshold on each block device. The value is specified in
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bytes, optionally with a K, M, or G suffix, case insensitive.
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Default is 1MB.
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.TP
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.B autodefrag
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Disable/enable auto defragmentation.
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Auto defragmentation detects small random writes into files and queue
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them up for the defrag process. Works best for small files;
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Not well suited for large database workloads.
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.TP
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\fBcheck_int\fP|\fBcheck_int_data\fP|\fBcheck_int_print_mask=\fP\,\fIvalue\fP
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These debugging options control the behavior of the integrity checking
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module(the BTRFS_FS_CHECK_INTEGRITY config option required).
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.B check_int
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enables the integrity checker module, which examines all
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block write requests to ensure on-disk consistency, at a large
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memory and CPU cost.
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.B check_int_data
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includes extent data in the integrity checks, and
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implies the check_int option.
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.B check_int_print_mask
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takes a bitmask of BTRFSIC_PRINT_MASK_* values
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as defined in fs/btrfs/check-integrity.c, to control the integrity
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checker module behavior.
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See comments at the top of
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.IR fs/btrfs/check-integrity.c
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for more info.
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.TP
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.BI commit= seconds
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Set the interval of periodic commit, 30 seconds by default. Higher
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values defer data being synced to permanent storage with obvious
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consequences when the system crashes. The upper bound is not forced,
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but a warning is printed if it's more than 300 seconds (5 minutes).
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.TP
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\fBcompress\fP|\fBcompress=\fP\,\fItype\fP|\fBcompress-force\fP|\fBcompress-force=\fP\,\fItype\fP
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Control BTRFS file data compression. Type may be specified as "zlib"
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"lzo" or "no" (for no compression, used for remounting). If no type
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is specified, zlib is used. If compress-force is specified,
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all files will be compressed, whether or not they compress well.
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If compression is enabled, nodatacow and nodatasum are disabled.
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.TP
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.B degraded
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Allow mounts to continue with missing devices. A read-write mount may
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fail with too many devices missing, for example if a stripe member
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is completely missing.
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.TP
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.BI device= devicepath
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Specify a device during mount so that ioctls on the control device
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can be avoided. Especially useful when trying to mount a multi-device
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setup as root. May be specified multiple times for multiple devices.
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.TP
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.B discard
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Disable/enable discard mount option.
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Discard issues frequent commands to let the block device reclaim space
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freed by the filesystem.
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This is useful for SSD devices, thinly provisioned
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LUNs and virtual machine images, but may have a significant
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performance impact. (The fstrim command is also available to
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initiate batch trims from userspace).
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.TP
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.B enospc_debug
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Disable/enable debugging option to be more verbose in some ENOSPC conditions.
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.TP
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.BI fatal_errors= action
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Action to take when encountering a fatal error:
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"bug" - BUG() on a fatal error. This is the default.
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"panic" - panic() on a fatal error.
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.TP
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.B flushoncommit
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The
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.B flushoncommit
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mount option forces any data dirtied by a write in a
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prior transaction to commit as part of the current commit. This makes
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the committed state a fully consistent view of the file system from the
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application's perspective (i.e., it includes all completed file system
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operations). This was previously the behavior only when a snapshot is
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created.
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.TP
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.B inode_cache
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Enable free inode number caching. Defaults to off due to an overflow
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problem when the free space crcs don't fit inside a single page.
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.TP
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.BI max_inline= bytes
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Specify the maximum amount of space, in bytes, that can be inlined in
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a metadata B-tree leaf. The value is specified in bytes, optionally
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with a K, M, or G suffix, case insensitive. In practice, this value
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is limited by the root sector size, with some space unavailable due
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to leaf headers. For a 4k sectorsize, max inline data is ~3900 bytes.
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.TP
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.BI metadata_ratio= value
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Specify that 1 metadata chunk should be allocated after every
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.IRvalue
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data chunks. Off by default.
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.TP
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.B noacl
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Enable/disable support for Posix Access Control Lists (ACLs). See the
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.B acl(5)
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manual page for more information about ACLs.
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.TP
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.B nobarrier
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Enable/disable the use of block layer write barriers. Write barriers
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ensure that certain IOs make it through the device cache and are on
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persistent storage. If disabled on a device with a volatile
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(non-battery-backed) write-back cache, nobarrier option will lead to
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filesystem corruption on a system crash or power loss.
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.TP
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.B nodatacow
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Enable/disable data copy-on-write for newly created files.
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Nodatacow implies nodatasum, and disables all compression.
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.TP
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.B nodatasum
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Enable/disable data checksumming for newly created files.
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Datasum implies datacow.
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.TP
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.B notreelog
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Enable/disable the tree logging used for fsync and O_SYNC writes.
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.TP
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.B recovery
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Enable autorecovery attempts if a bad tree root is found at mount time.
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Currently this scans a list of several previous tree roots and tries to
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use the first readable.
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.TP
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.B rescan_uuid_tree
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Force check and rebuild procedure of the UUID tree. This should not
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normally be needed.
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.TP
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.B skip_balance
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Skip automatic resume of interrupted balance operation after mount.
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May be resumed with "btrfs balance resume."
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.TP
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.B nospace_cache
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Disable freespace cache loading without clearing the cache.
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.TP
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.B clear_cache
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Force clearing and rebuilding of the disk space cache if something
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has gone wrong.
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.TP
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.BR ssd | nossd | ssd_spread
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Options to control ssd allocation schemes. By default, BTRFS will
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enable or disable ssd allocation heuristics depending on whether a
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rotational or nonrotational disk is in use. The ssd and nossd options
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can override this autodetection.
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The ssd_spread mount option attempts to allocate into big chunks
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of unused space, and may perform better on low-end ssds. ssd_spread
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implies ssd, enabling all other ssd heuristics as well.
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.TP
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.BI subvol= path
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Mount subvolume at
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.IR path
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rather than the root subvolume. The
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.IR path
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is relative to the top level subvolume.
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.TP
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.BI subvolid= ID
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Mount subvolume specified by an ID number rather than the root subvolume.
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This allows mounting of subvolumes which are not in the root of the mounted
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filesystem.
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You can use "btrfs subvolume list" to see subvolume ID numbers.
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.TP
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.BI subvolrootid= objectid (deprecated)
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Mount subvolume specified by
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.IR objectid
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rather than the root subvolume.
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This allows mounting of subvolumes which are not in the root of the mounted
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filesystem.
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You can use "btrfs subvolume show " to see the object ID for a subvolume.
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.TP
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.BI thread_pool= number
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The number of worker threads to allocate. The default number is equal
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to the number of CPUs + 2, or 8, whichever is smaller.
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.TP
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.B user_subvol_rm_allowed
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Allow subvolumes to be deleted by a non-root user. Use with caution.
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.SH "Mount options for cifs"
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See the options section of the
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