BCACHEFS(8) System Manager's Manual (smm) BCACHEFS(8) NAME bcachefs - manage bcachefs filesystems/devices SYNOPSIS bcachefs command [options] [arguments] DESCRIPTION The bcachefs utility supports the following subcommands, which are documented in detail below: Superblock commands format Format one or a list of devices with bcachefs data structures. show-super Dump superblock information to stdout. set-fs-option Set a filesystem option Mount commands mount Mount a filesystem. Repair commands fsck Check an existing filesystem for errors. Commands for managing a running filesystem fs usage Show disk usage fs top Show runtime performance information Commands for managing devices within a running filesystem device add Add a new device to an existing filesystem device remove Remove a device from an existing filesystem device online Re-add an existing member to a filesystem device offline Take a device offline, without removing it device evacuate Migrate data off of a specific device device set-state Set a device state device resize Resize filesystem on a device device resize-journal Resize journal on a device Commands for managing subvolumes and snapshots subvolume create Create a new subvolume subvolume delete Delete an existing subvolume subvolume snapshot Create a snapshot subvolume list List subvolumes subvolume list-snapshots List snapshots and their disk usage Commands for managing filesystem data reconcile Query or wait for background data reconciliation scrub Verify data checksums Commands for encryption unlock Unlock an encrypted filesystem prior to running/mounting set-passphrase Change passphrase on an existing (unmounted) filesystem remove-passphrase Remove passphrase on an existing (unmounted) filesystem Commands for migration migrate Migrate an existing filesystem to bcachefs, in place migrate-superblock Add default superblock, after bcachefs migrate Commands for operating on files in a bcachefs filesystem set-file-option Set various per file attributes Commands for debugging dump Dump filesystem metadata to a qcow2 image list List filesystem metadata in textual form list_journal List contents of journal FUSE commands fusemount Mount a filesystem via FUSE Miscellaneous commands version Display the version of the invoked bcachefs tool completions Generate shell completions Superblock commands bcachefs format [options] devices ... Format one or a list of devices with bcachefs data structures. You need to do this before you create a volume. Device specific options must come before corresponding devices, e.g. bcachefs format --label=ssd /dev/sda --label=hdd /dev/sdb --block_size=size block size, in bytes (e.g. 4k) --btree_node_size=size Btree node size, default 256k --errors=(continue | ro | panic) Action to take on filesystem error --data_replicas=number Number of data replicas. With erasure coding enabled, this is currently capped at 3 (RAID6). --metadata_replicas=number Number of metadata replicas --encoded_extent_max=size Maximum size of checksummed/compressed extents --metadata_checksum=(none | crc32c | crc64 | xxhash) Set metadata checksum type (default: crc32c). --data_checksum=(none | crc32c | crc64 | xxhash) Set data checksum type (default: crc32c). --compression=(none | lz4 | gzip | zstd) Set compression type (default: none). --background_compression=(none | lz4 | gzip | zstd) --str_hash=(crc32c | crc64 | siphash) Hash function for directory entries and xattrs --metadata_target=target Device or label for metadata writes --foreground_target=target Device or label for foreground writes --background_target=target Device or label to move data to in the background --promote_target=target Device or label to promote data to on read --erasure_code Enable erasure coding (RAID5/6; data replicas are capped at 3) --inodes_32bit Constrain inode numbers to 32 bits --shared_inode_numbers Shared new inode numbers by CPU id --inodes_use_key_cache Use the btree key cache for the inodes btree --gc_reserve_percent=percentage Percentage of disk space to reserve for copygc --gc_reserve_bytes=percentage Amount of disk space to reserve for copygc This takes precedence over gc_reserve_percent if set --root_reserve_percent=percentage Percentage of disk space to reserve for superuser --wide_macs Store full 128bits of cryptographic MACS, instead of 80 --acl Enable POSIX acls --usrquota Enable user quotas --grpquota Enable group quotas --prjquota Enable project quotas --journal_transaction_names Log transaction function names in journal --nocow Nocow mode: Writes will be done in place when possible. Snapshots and reflink will still cause writes to be COW. This flag implicitly disables data checksumming, compression and encryption. --replicas=number Sets both data and metadata replicas. --encrypted Enable whole filesystem encryption (chacha20/poly1305); passphrase will be prompted for. --no_passphrase Store master encryption key unencrypted in superblock -L, --fs_label=label Create the filesystem with the specified label This is the filesystem label, distinct from per-device labels used for target selection. On a mounted filesystem it can be changed by tools that issue the standard Linux FS_IOC_SETFSLABEL ioctl. -U, --uuid=uuid Create the filesystem with the specified uuid --superblock_size=size Device specific options: --discard Enable discard/TRIM support --fs_size=size Create the filesystem using size bytes on the subsequent device. --bucket=size Specifies the bucket size; must be greater than the btree node size --durability=n Data written to this device will be considered to have already been replicated n times -l, --label Disk label -f, --force Force the filesystem to be created, even if the device already contains a filesystem. -q, --quiet Only print errors -v, --verbose Verbose filesystem initialization bcachefs show-super [options] device Dump superblock information to stdout. -f, --fields=fields List of sections to print -l, --layout Print superblock layout bcachefs set-fs-option [options] device --errors=(continue | ro | panic) Action to take on filesystem error --metadata_replicas=number Number of metadata replicas --data_replicas=number Number of data replicas. With erasure coding enabled, this is currently capped at 3 (RAID6). --metadata_checksum=(none | crc32c | crc64 | xxhash) Set metadata checksum type (default: crc32c). --data_checksum=(none | crc32c | crc64 | xxhash) Set data checksum type (default: crc32c). --compression=(none | lz4 | gzip | zstd) Set compression type (default: none). --background_compression=(none | lz4 | gzip | zstd) --str_hash=(crc32c | crc64 | siphash) Hash function for directory entries and xattrs --metadata_target=target Device or label for metadata writes --foreground_target=target Device or label for foreground writes --background_target=target Device or label to move data to in the background --promote_target=target Device or label to promote data to on read --erasure_code Enable erasure coding (RAID5/6; data replicas are capped at 3) --inodes_32bit Constrain inode numbers to 32 bits --shared_inode_numbers Shared new inode numbers by CPU id --inodes_use_key_cache Use the btree key cache for the inodes btree --gc_reserve_percent=percentage Percentage of disk space to reserve for copygc --gc_reserve_bytes=percentage Amount of disk space to reserve for copygc This takes precedence over gc_reserve_percent if set --root_reserve_percent=percentage Percentage of disk space to reserve for superuser --wide_macs Store full 128bits of cryptographic MACS, instead of 80 --acl Enable POSIX acls --usrquota Enable user quotas --grpquota Enable group quotas --prjquota Enable project quotas --degraded Allow mounting in degraded mode --very_degraded Allow mounting in when data will be missing --discard Enable discard/TRIM support --verbose Extra debugging information during mount/recovery --journal_flush_delay=ms Delay in milliseconds before automatic journal commits --journal_flush_disabled Disable journal flush on sync/fsync If enabled, writes can be lost, but only since the last journal write (default 1 second) --journal_reclaim_delay=ms Delay in milliseconds before automatic journal reclaim --move_bytes_in_flight=bytes Maximum Amount of IO to keep in flight by the move path --move_ios_in_flight=number Maximum number of IOs to keep in flight by the move path --fsck Run fsck on mount --fix_errors=error Fix errors during fsck without asking --ratelimit_errors Ratelimit error messages during fsck --nochanges Super read only mode - no writes at all will be issued, even if we have to replay the journal --norecovery Don't replay the journal --journal_transaction_names Log transaction function names in journal --noexcl Don't open device in exclusive mode --direct_io Use O_DIRECT (userspace only) --sb=offset Sector offset of superblock --reconstruct_alloc Reconstruct alloc btree --version_upgrade=(compatible | incompatible | none) Set superblock to latest version, allowing any new features to be used compatible is the default: compatible metadata upgrades may be applied automatically, and the filesystem may still downgrade those compatible version fields when mounted by an older kernel. Use incompatible only for an intentional one-way metadata upgrade that may prevent mounting with older kernels, and use none to avoid optional version upgrades. --nocow Nocow mode: Writes will be done in place when possible. Snapshots and reflink will still cause writes to be COW. This flag implicitly disables data checksumming, compression and encryption. --nocow_enabled Enable nocow mode: enables runtime locking in data move path needed if nocow will ever be in use --no_data_io Skip submit_bio() for data reads and writes, for performance testing purposes Mount commands bcachefs mount [options] device mountpoint The mount -t bcachefs path invokes the installed mount.bcachefs helper; this is the same mount path exposed as bcachefs mount. Mount a filesystem. The device can be a device, a colon-separated list of devices, UUID=, OLD_BLKID_UUID=, or LABEL=