diff options
Diffstat (limited to 'Documentation/filesystems/btrfs.txt')
| -rw-r--r-- | Documentation/filesystems/btrfs.txt | 81 |
1 files changed, 47 insertions, 34 deletions
diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt index 9dae5940743..d11cc2f8077 100644 --- a/Documentation/filesystems/btrfs.txt +++ b/Documentation/filesystems/btrfs.txt @@ -38,7 +38,7 @@ Mount Options ============= When mounting a btrfs filesystem, the following option are accepted. -Unless otherwise specified, all options default to off. +Options with (*) are default options and will not show in the mount options. alloc_start=<bytes> Debugging option to force all block allocations above a certain @@ -46,10 +46,12 @@ Unless otherwise specified, all options default to off. bytes, optionally with a K, M, or G suffix, case insensitive. Default is 1MB. + noautodefrag(*) autodefrag - Detect 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. + 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. check_int check_int_data @@ -70,6 +72,12 @@ Unless otherwise specified, all options default to off. See comments at the top of fs/btrfs/check-integrity.c for more info. + 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). + compress compress=<type> compress-force @@ -90,21 +98,26 @@ Unless otherwise specified, all options default to off. can be avoided. Especially useful when trying to mount a multi-device setup as root. May be specified multiple times for multiple devices. + nodiscard(*) discard - Issue frequent commands to let the block device reclaim space freed by - the filesystem. This is useful for SSD devices, thinly provisioned + 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). + noenospc_debug(*) enospc_debug - Debugging option to be more verbose in some ENOSPC conditions. + Disable/enable debugging option to be more verbose in some ENOSPC conditions. 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. + noflushoncommit(*) flushoncommit 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 @@ -128,33 +141,43 @@ Unless otherwise specified, all options default to off. Specify that 1 metadata chunk should be allocated after every <value> data chunks. Off by default. + acl(*) noacl - Disable support for Posix Access Control Lists (ACLs). See the + Enable/disable support for Posix Access Control Lists (ACLs). See the acl(5) manual page for more information about ACLs. + barrier(*) nobarrier - Disables 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 used on a device with a volatile (non-battery-backed) - write-back cache, this option will lead to filesystem corruption on a - system crash or power loss. + 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. + datacow(*) nodatacow - Disable data copy-on-write for newly created files. Implies nodatasum, - and disables all compression. + Enable/disable data copy-on-write for newly created files. + Nodatacow implies nodatasum, and disables all compression. + datasum(*) nodatasum - Disable data checksumming for newly created files. + Enable/disable data checksumming for newly created files. + Datasum implies datacow. + treelog(*) notreelog - Disable the tree logging used for fsync and O_SYNC writes. + Enable/disable the tree logging used for fsync and O_SYNC writes. 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. - skip_balance + rescan_uuid_tree + Force check and rebuild procedure of the UUID tree. This should not + normally be needed. + + skip_balance Skip automatic resume of interrupted balance operation after mount. May be resumed with "btrfs balance resume." @@ -234,24 +257,14 @@ available from the git repository at the following location: These include the following tools: -mkfs.btrfs: create a filesystem - -btrfsctl: control program to create snapshots and subvolumes: +* mkfs.btrfs: create a filesystem - mount /dev/sda2 /mnt - btrfsctl -s new_subvol_name /mnt - btrfsctl -s snapshot_of_default /mnt/default - btrfsctl -s snapshot_of_new_subvol /mnt/new_subvol_name - btrfsctl -s snapshot_of_a_snapshot /mnt/snapshot_of_new_subvol - ls /mnt - default snapshot_of_a_snapshot snapshot_of_new_subvol - new_subvol_name snapshot_of_default +* btrfs: a single tool to manage the filesystems, refer to the manpage for more details - Snapshots and subvolumes cannot be deleted right now, but you can - rm -rf all the files and directories inside them. +* 'btrfsck' or 'btrfs check': do a consistency check of the filesystem -btrfsck: do a limited check of the FS extent trees. +Other tools for specific tasks: -btrfs-debug-tree: print all of the FS metadata in text form. Example: +* btrfs-convert: in-place conversion from ext2/3/4 filesystems - btrfs-debug-tree /dev/sda2 >& big_output_file +* btrfs-image: dump filesystem metadata for debugging |