btrfs scrub <subcommand> <args>
- cancel <path>|<device>
If a scrub is running on the filesystem identified by path or device, cancel it.
If a device is specified, the corresponding filesystem is found and :command:`btrfs scrub cancel` behaves as if it was called on that filesystem. The progress is saved in the status file so :command:`btrfs scrub resume` can continue from the last position.
- limit [options] <path>
Show or set scrub limits on devices of the given filesystem.
Options- -d|--devid DEVID
- select the device by DEVID to apply the limit
- -l|--limit SIZE
- set the limit of the device to SIZE (size units with suffix), or 0 to reset to unlimited
- -a|--all
- apply the limit to all devices
--raw print all numbers raw values in bytes without the B suffix --human-readable print human friendly numbers, base 1024, this is the default --iec select the 1024 base for the following options, according to the IEC standard --si select the 1000 base for the following options, according to the SI standard --kbytes show sizes in KiB, or kB with --si --mbytes show sizes in MiB, or MB with --si --gbytes show sizes in GiB, or GB with --si --tbytes show sizes in TiB, or TB with --si - resume [-BdqrR] <path>|<device>
Resume a cancelled or interrupted scrub on the filesystem identified by path or on a given device. The starting point is read from the status file if it exists.
This does not start a new scrub if the last scrub finished successfully.
Options
- start [options] <path>|<device>
Start a scrub on all devices of the mounted filesystem identified by path or on a single device. If a scrub is already running, the new one will not start. A device of an unmounted filesystem cannot be scrubbed this way.
Without options, scrub is started as a background process. The automatic repairs of damaged copies are performed by default for block group profiles with redundancy. No-repair can be enabled by option -r.
Options-B do not background and print scrub statistics when finished -d print separate statistics for each device of the filesystem (-B only) at the end -r run in read-only mode, do not attempt to correct anything, can be run on a read-only filesystem
Note that a read-only scrub on a read-write filesystem can still cause writes into the filesystem due to some internal limitations. Only a read-only scrub on a read-only filesystem can avoid writes from scrub.
-R raw print mode, print full data instead of summary --limit <limit> set the scrub throughput limit for each device.
If the scrub is for the whole fs, it's the same as :command:`btrfs scrub limit -a -l <value>`. If the scrub is for a single device, it's the same as :command:`btrfs scrub limit -d <devid> -l <value>`.
The value is bytes per second, and accepts the usual KMGT prefixes. After the scrub is finished, the throughput limit will be reset to the old value of each device.
-f force starting new scrub even if a scrub is already running, this can useful when scrub status file is damaged and reports a running scrub although it is not, but should not normally be necessary Deprecated options-c <ioprio_class> set IO priority class (see :manref:`ionice(1)` manual page) if the IO scheduler configured for the device supports ionice. This is only supported by BFQ or Kyber but is not supported by mq-deadline. Please read the section about :docref:`IO limiting <btrfs-scrub:scrub-io-limiting>`. -n <ioprio_classdata> set IO priority classdata (see :manref:`ionice(1)` manpage) -q (deprecated) alias for global -q option - status [options] <path>|<device>
Show status of a running scrub for the filesystem identified by path or for the specified device.
If no scrub is running, show statistics of the last finished or cancelled scrub for that filesystem or device.
Options-d print separate statistics for each device of the filesystem -R print all raw statistics without postprocessing as returned by the status ioctl --raw print all numbers raw values in bytes without the B suffix --human-readable print human friendly numbers, base 1024, this is the default --iec select the 1024 base for the following options, according to the IEC standard --si select the 1000 base for the following options, according to the SI standard --kbytes show sizes in KiB, or kB with --si --mbytes show sizes in MiB, or MB with --si --gbytes show sizes in GiB, or GB with --si --tbytes show sizes in TiB, or TB with --si A status on a filesystem without any error looks like the following:
# btrfs scrub start / # btrfs scrub status / UUID: 76fac721-2294-4f89-a1af-620cde7a1980 Scrub started: Wed Apr 10 12:34:56 2023 Status: running Duration: 0:00:05 Time left: 0:00:05 ETA: Wed Apr 10 12:35:01 2023 Total to scrub: 28.32GiB Bytes scrubbed: 13.76GiB (48.59%) Rate: 2.75GiB/s Error summary: no errors found
With some errors found:
Error summary: csum=72 Corrected: 2 Uncorrectable: 72 Unverified: 0
- Corrected -- number of bad blocks that were repaired from another copy
- Uncorrectable -- errors detected at read time but not possible to repair from other copy
- Unverified -- transient errors, first read failed but a retry succeeded, may be affected by lower layers that group or split IO requests
- Error summary -- followed by a more detailed list of errors found
- csum -- checksum mismatch
- super -- super block errors, unless the error is fixed immediately, the next commit will overwrite superblock
- verify -- metadata block header errors
- read -- blocks can't be read due to IO errors
It's possible to set a per-device limit via file :file:`sysfs/fs/btrfs/FSID/devinfo/scrub_speed_max`. In that case the limit is printed on the Rate: line if option -d is specified, or without it on a single-device filesystem. Read more about tat in section about :docref:`scrub IO limiting <btrfs-scrub:scrub-io-limiting>`.
Rate: 989.0MiB/s (limit 1.0G/s)
On a multi-device filesystem with at least one device limit the overall stats cannot print the limit without -d so there's a not that some limits are set:
Rate: 36.37MiB/s (some device limits set)
btrfs scrub returns a zero exit status if it succeeds. Non zero is returned in case of failure:
- 1
- scrub couldn't be performed
- 2
- there is nothing to resume
- 3
- scrub found uncorrectable errors
btrfs is part of btrfs-progs. Please refer to the documentation at https://btrfs.readthedocs.io.