path: root/Documentation
diff options
authorDavid Sterba <>2017-08-31 18:34:37 +0200
committerDavid Sterba <>2017-09-08 16:15:05 +0200
commit162fdf95383bd6685cce17f9c52cc858fef2c09c (patch)
tree8c767bcce1ce252a6740438a3c3bb0c3dd4f9768 /Documentation
parent8609c8bad68528f668d9ce564b868aa4828107a0 (diff)
btrfs-progs: check: add option to skip mount checks
Sometimes it's needed to do a check on a mounted filesystem. This should work fine on a quiescent filesystem or a read-only mount. Changes on the block device done by kernel might confuse the userspace checker and it might crash when it reads some stale data. Repair without mount checks is not supported right now. Signed-off-by: David Sterba <>
Diffstat (limited to 'Documentation')
1 files changed, 10 insertions, 2 deletions
diff --git a/Documentation/btrfs-check.asciidoc b/Documentation/btrfs-check.asciidoc
index fa054e45..fbf48847 100644
--- a/Documentation/btrfs-check.asciidoc
+++ b/Documentation/btrfs-check.asciidoc
@@ -3,7 +3,7 @@ btrfs-check(8)
-btrfs-check - check or repair an unmounted btrfs filesystem
+btrfs-check - check or repair a btrfs filesystem
@@ -13,7 +13,9 @@ DESCRIPTION
The filesystem checker is used to verify structural integrity of a filesystem
-and attempt to repair it if requested. The filesystem must be unmounted.
+and attempt to repair it if requested. It is recommended to unmount the
+filesystem prior to running the check, but it is possible to start checking a
+mounted filesystem (see '--force').
By default, *btrfs check* will not modify the device but you can reaffirm that
by the option '--readonly'.
@@ -120,6 +122,12 @@ needs to re-read blocks when needed. This may increase run time.
NOTE: 'lowmem' mode does not work with '--repair' yet, and is still considered
+allow to work on a mounted filesystem. Note that this should work fine on a
+quiescent or read-only mounted filesystem but may crash if the device is
+changed externally, eg. by the kernel module. Repair without mount checks is
+not supported right now.
*btrfs check* returns a zero exit status if it succeeds. Non zero is