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Diffstat (limited to 'Documentation/btrfs-man5.asciidoc')
| -rw-r--r-- | Documentation/btrfs-man5.asciidoc | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/Documentation/btrfs-man5.asciidoc b/Documentation/btrfs-man5.asciidoc index 7dd323fa..467f11bf 100644 --- a/Documentation/btrfs-man5.asciidoc +++ b/Documentation/btrfs-man5.asciidoc @@ -14,6 +14,8 @@ tools. Currently covers: 2. file attributes +3. control device + MOUNT OPTIONS ------------- @@ -455,11 +457,43 @@ When set on a directory, all newly created files will inherit this attribute. No other attributes are supported. For the complete list please refer to the `chattr`(1) manual page. +CONTROL DEVICE +-------------- + +There's a character special device `/dev/btrfs-control` with major and minor +numbers 10 and 234 (the device can be found under the 'misc' category). + +-------------------- +$ ls -l /dev/btrfs-control +crw------- 1 root root 10, 234 Jan 1 12:00 /dev/btrfs-control +-------------------- + +The device accepts some ioctl calls that can perform following actions on the +filesyste module: + +* scan devices for btrfs filesytem (ie. to let multi-device filesystems mount + automatically) and register them with the kernel module +* similar to scan, but also wait until the device scanning process is finished + for a given filesystem +* get the supported features (can be also found under '/sys/fs/btrfs/features') + + +The device is usually created by ..., but can be created manually: + +-------------------- +# mknod --mode=600 c 10 234 /dev/btrfs-control +-------------------- + +The device is not strictly required but the device scanning will not work and a +workaround would need to be used to mount a multi-device filesystem. The mount +option 'device' can trigger the device scanning during mount. + SEE ALSO -------- `acl`(5), `btrfs`(8), `chattr`(1), `fstrim`(8), +`ioctl`(2), `mkfs.btrfs`(8), `mount`(8) |