Based on Documentation/filesystems/btrfs.txt Signed-off-by: Gui Hecheng <guihc.fnst@xxxxxxxxxxxxxx> --- sys-utils/mount.8 | 186 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 186 insertions(+) diff --git a/sys-utils/mount.8 b/sys-utils/mount.8 index efa1ae8..ec8eab3 100644 --- a/sys-utils/mount.8 +++ b/sys-utils/mount.8 @@ -671,6 +671,7 @@ currently supported include: .IR adfs , .IR affs , .IR autofs , +.IR btrfs , .IR cifs , .IR coda , .IR coherent , @@ -1245,6 +1246,191 @@ Give blocksize. Allowed values are 512, 1024, 2048, 4096. These options are accepted but ignored. (However, quota utilities may react to such strings in .IR /etc/fstab .) +.SH "Mount options for btrfs" +Btrfs is a copy on write filesystem for Linux aimed at +implementing advanced features while focusing on fault tolerance, +repair and easy administration. +.TP +.BI alloc_start= bytes +Debugging option to force all block allocations above a certain +byte threshold on each block device. The value is specified in +bytes, optionally with a K, M, or G suffix, case insensitive. +Default is 1MB. +.TP +.B autodefrag +Disable/enable auto defragmentation. +Auto defragmentation detects small random writes into files and queue +them up for the defrag process. Works best for small files; +Not well suited for large database workloads. +.TP +\fBcheck_int\fP|\fBcheck_int_data\fP|\fBcheck_int_print_mask=\fP\,\fIvalue\fP +These debugging options control the behavior of the integrity checking +module(the BTRFS_FS_CHECK_INTEGRITY config option required). + +.B check_int +enables the integrity checker module, which examines all +block write requests to ensure on-disk consistency, at a large +memory and CPU cost. + +.B check_int_data +includes extent data in the integrity checks, and +implies the check_int option. + +.B check_int_print_mask +takes a bitmask of BTRFSIC_PRINT_MASK_* values +as defined in fs/btrfs/check-integrity.c, to control the integrity +checker module behavior. + +See comments at the top of +.IR fs/btrfs/check-integrity.c +for more info. +.TP +.BI commit= seconds +Set the interval of periodic commit, 30 seconds by default. Higher +values defer data being synced to permanent storage with obvious +consequences when the system crashes. The upper bound is not forced, +but a warning is printed if it's more than 300 seconds (5 minutes). +.TP +\fBcompress\fP|\fBcompress=\fP\,\fItype\fP|\fBcompress-force\fP|\fBcompress-force=\fP\,\fItype\fP +Control BTRFS file data compression. Type may be specified as "zlib" +"lzo" or "no" (for no compression, used for remounting). If no type +is specified, zlib is used. If compress-force is specified, +all files will be compressed, whether or not they compress well. +If compression is enabled, nodatacow and nodatasum are disabled. +.TP +.B degraded +Allow mounts to continue with missing devices. A read-write mount may +fail with too many devices missing, for example if a stripe member +is completely missing. +.TP +.BI device= devicepath +Specify a device during mount so that ioctls on the control device +can be avoided. Especially useful when trying to mount a multi-device +setup as root. May be specified multiple times for multiple devices. +.TP +.B discard +Disable/enable discard mount option. +Discard issues frequent commands to let the block device reclaim space +freed by the filesystem. +This is useful for SSD devices, thinly provisioned +LUNs and virtual machine images, but may have a significant +performance impact. (The fstrim command is also available to +initiate batch trims from userspace). +.TP +.B enospc_debug +Disable/enable debugging option to be more verbose in some ENOSPC conditions. +.TP +.BI fatal_errors= action +Action to take when encountering a fatal error: + "bug" - BUG() on a fatal error. This is the default. + "panic" - panic() on a fatal error. +.TP +.B flushoncommit +The +.B flushoncommit +mount option forces any data dirtied by a write in a +prior transaction to commit as part of the current commit. This makes +the committed state a fully consistent view of the file system from the +application's perspective (i.e., it includes all completed file system +operations). This was previously the behavior only when a snapshot is +created. +.TP +.B inode_cache +Enable free inode number caching. Defaults to off due to an overflow +problem when the free space crcs don't fit inside a single page. +.TP +.BI max_inline= bytes +Specify the maximum amount of space, in bytes, that can be inlined in +a metadata B-tree leaf. The value is specified in bytes, optionally +with a K, M, or G suffix, case insensitive. In practice, this value +is limited by the root sector size, with some space unavailable due +to leaf headers. For a 4k sectorsize, max inline data is ~3900 bytes. +.TP +.BI metadata_ratio= value +Specify that 1 metadata chunk should be allocated after every +.IRvalue +data chunks. Off by default. +.TP +.B noacl +Enable/disable support for Posix Access Control Lists (ACLs). See the +.B acl(5) +manual page for more information about ACLs. +.TP +.B nobarrier +Enable/disable the use of block layer write barriers. Write barriers +ensure that certain IOs make it through the device cache and are on +persistent storage. If disabled on a device with a volatile +(non-battery-backed) write-back cache, nobarrier option will lead to +filesystem corruption on a system crash or power loss. +.TP +.B nodatacow +Enable/disable data copy-on-write for newly created files. +Nodatacow implies nodatasum, and disables all compression. +.TP +.B nodatasum +Enable/disable data checksumming for newly created files. +Datasum implies datacow. +.TP +.B notreelog +Enable/disable the tree logging used for fsync and O_SYNC writes. +.TP +.B recovery +Enable autorecovery attempts if a bad tree root is found at mount time. +Currently this scans a list of several previous tree roots and tries to +use the first readable. +.TP +.B rescan_uuid_tree +Force check and rebuild procedure of the UUID tree. This should not +normally be needed. +.TP +.B skip_balance +Skip automatic resume of interrupted balance operation after mount. +May be resumed with "btrfs balance resume." +.TP +.B nospace_cache +Disable freespace cache loading without clearing the cache. +.TP +.B clear_cache +Force clearing and rebuilding of the disk space cache if something +has gone wrong. +.TP +.BR ssd | nossd | ssd_spread +Options to control ssd allocation schemes. By default, BTRFS will +enable or disable ssd allocation heuristics depending on whether a +rotational or nonrotational disk is in use. The ssd and nossd options +can override this autodetection. + +The ssd_spread mount option attempts to allocate into big chunks +of unused space, and may perform better on low-end ssds. ssd_spread +implies ssd, enabling all other ssd heuristics as well. +.TP +.BI subvol= path +Mount subvolume at +.IR path +rather than the root subvolume. The +.IR path +is relative to the top level subvolume. +.TP +.BI subvolid= ID +Mount subvolume specified by an ID number rather than the root subvolume. +This allows mounting of subvolumes which are not in the root of the mounted +filesystem. +You can use "btrfs subvolume list" to see subvolume ID numbers. +.TP +.BI subvolrootid= objectid (deprecated) +Mount subvolume specified by +.IR objectid +rather than the root subvolume. +This allows mounting of subvolumes which are not in the root of the mounted +filesystem. +You can use "btrfs subvolume show " to see the object ID for a subvolume. +.TP +.BI thread_pool= number +The number of worker threads to allocate. The default number is equal +to the number of CPUs + 2, or 8, whichever is smaller. +.TP +.B user_subvol_rm_allowed +Allow subvolumes to be deleted by a non-root user. Use with caution. .SH "Mount options for cifs" See the options section of the -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe util-linux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
