MOUNT OPTIONS
-------------
*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.
+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.
*autodefrag*::
*noautodefrag*::
- (since: 3.0, default: off) +
- 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.
- +
- WARNING: Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as
- well as with Linux stable kernel versions ≥ 3.10.31, ≥ 3.12.12 or
- ≥ 3.13.4 will break up the ref-links of CoW data (for example files
- copied with `cp --reflink`, snapshots or de-duplicated data).
- This may cause considerable increase of space usage depending on the
- broken up ref-links.
+(since: 3.0, default: off) +
+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.
++
+WARNING: Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as
+well as with Linux stable kernel versions ≥ 3.10.31, ≥ 3.12.12 or
+≥ 3.13.4 will break up the ref-links of CoW data (for example files
+copied with `cp --reflink`, snapshots or de-duplicated data).
+This may cause considerable increase of space usage depending on the
+broken up ref-links.
*check_int*::
*check_int_data*::
*check_int_print_mask='value'*::
- (since: 3.0, default: off) +
- These debugging options control the behavior of the integrity checking
- module (the BTRFS_FS_CHECK_INTEGRITY config option required). +
- +
- `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. +
- +
- `check_int_data` includes extent data in the integrity checks, and
- implies the check_int option. +
- +
- `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 'fs/btrfs/check-integrity.c'
- for more info.
+(since: 3.0, default: off) +
+These debugging options control the behavior of the integrity checking
+module (the BTRFS_FS_CHECK_INTEGRITY config option required). +
++
+`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. +
++
+`check_int_data` includes extent data in the integrity checks, and
+implies the check_int option. +
++
+`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 'fs/btrfs/check-integrity.c'
+for more info.
*commit='seconds'*::
- (since: 3.12, default: 30) +
- Set the interval of periodic commit. 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).
+(since: 3.12, default: 30) +
+Set the interval of periodic commit. 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).
*compress*::
*compress='type'*::
*compress-force*::
*compress-force='type'*::
- (default: off) +
- 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.
- NOTE: If compression is enabled, 'nodatacow' and 'nodatasum' are disabled.
+(default: off) +
+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.
+NOTE: If compression is enabled, 'nodatacow' and 'nodatasum' are disabled.
*degraded*::
- (default: off) +
- 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.
+(default: off) +
+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.
*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.
+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.
*discard*::
*nodiscard*::
- (default: off) +
- 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).
+(default: off) +
+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).
*enospc_debug*::
- (default: off) +
- Disable/enable debugging option to be more verbose in some ENOSPC conditions.
+(default: off) +
+Disable/enable debugging option to be more verbose in some ENOSPC conditions.
*fatal_errors='action'*::
- (since: 3.4, default: bug) +
- Action to take when encountering a fatal error. +
- "bug" - BUG() on a fatal error. +
- "panic" - panic() on a fatal error.
+(since: 3.4, default: bug) +
+Action to take when encountering a fatal error. +
+ "bug" - BUG() on a fatal error. +
+ "panic" - panic() on a fatal error.
*flushoncommit*::
*noflushoncommit*::
- (default: on) +
- The `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.
+(default: on) +
+The `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.
*inode_cache*::
*noinode_cache*::
- (since: 3.0, default: off) +
- 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.
+(since: 3.0, default: off) +
+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.
*max_inline='bytes'*::
- (default: min(8192, page size) )
- 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.
+(default: min(8192, page size) )
+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.
*metadata_ratio='value'*::
- Specify that 1 metadata chunk should be allocated after every
- 'value' data chunks. Off by default.
+Specify that 1 metadata chunk should be allocated after every
+'value' data chunks. Off by default.
*acl*::
*noacl*::
- (default: on) +
- Enable/disable support for Posix Access Control Lists (ACLs). See the
- `acl`(5) manual page for more information about ACLs.
+(default: on) +
+Enable/disable support for Posix Access Control Lists (ACLs). See the
+`acl`(5) manual page for more information about ACLs.
*barrier*::
*nobarrier*::
- (default: on) +
- 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.
+(default: on) +
+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.
*datacow*::
*nodatacow*::
- (default: on) +
- Enable/disable data copy-on-write for newly created files.
- Nodatacow implies nodatasum, and disables all compression.
+(default: on) +
+Enable/disable data copy-on-write for newly created files.
+Nodatacow implies nodatasum, and disables all compression.
*datasum*::
*nodatasum*::
- (default: on) +
- Enable/disable data checksumming for newly created files.
- Datasum implies datacow.
+(default: on) +
+Enable/disable data checksumming for newly created files.
+Datasum implies datacow.
*treelog*::
*notreelog*::
- (default: on) +
- Enable/disable the tree logging used for fsync and O_SYNC writes.
+(default: on) +
+Enable/disable the tree logging used for fsync and O_SYNC writes.
*recovery*::
- (since: 3.2, default: off) +
- 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.
+(since: 3.2, default: off) +
+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.
*rescan_uuid_tree*::
- (since: 3.12, default: off) +
- Force check and rebuild procedure of the UUID tree. This should not
- normally be needed.
+(since: 3.12, default: off) +
+Force check and rebuild procedure of the UUID tree. This should not
+normally be needed.
*skip_balance*::
- (since: 3.3, default: off) +
- Skip automatic resume of interrupted balance operation after mount.
- May be resumed with "btrfs balance resume."
+(since: 3.3, default: off) +
+Skip automatic resume of interrupted balance operation after mount.
+May be resumed with "btrfs balance resume."
*nospace_cache*::
- (since: 3.2) +
- Disable freespace cache loading without clearing the cache.
+(since: 3.2) +
+Disable freespace cache loading without clearing the cache.
*clear_cache*::
- Force clearing and rebuilding of the disk space cache if something
- has gone wrong.
+Force clearing and rebuilding of the disk space cache if something
+has gone wrong.
*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.
+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.
*subvol='path'*::
- Mount subvolume at 'path' rather than the root subvolume. The
- 'path' is relative to the top level subvolume.
+Mount subvolume at 'path' rather than the root subvolume. The
+'path' is relative to the top level subvolume.
*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.
+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.
*subvolrootid='objectid'*::
- (deprecated) +
- Mount subvolume specified by '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.
+(deprecated) +
+Mount subvolume specified by '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.
*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.
+The number of worker threads to allocate. The default number is equal
+to the number of CPUs + 2, or 8, whichever is smaller.
*user_subvol_rm_allowed*::
- (default: off) +
- Allow subvolumes to be deleted by a non-root user. Use with caution.
+(default: off) +
+Allow subvolumes to be deleted by a non-root user. Use with caution.
FILE ATTRIBUTES
---------------
projects / platform / upstream / btrfs-progs.git / commitdiff