btrfs: Option to create read-only snapshot does not exist

[Stefan Lasiewski]

According to the Btrfs wiki [1], Btrfs supports read-only snapshots.

    NEWS
    Linux 2.6.38 released (March 2011) LZO compression. Forced read-only mode for handling filesystem errors. Read-only snapshots.

Read-only snapshots should be created with the command `btrfs subvolume snapshot -r volume nameofsnapshot [2] [3].

However, the option to support this does not exist on Ubuntu 11.10:

    $ btrfs subvolume snapshot -r /u1 /u1/.snapshot/test
    ERROR: 'subvolume snapshot' requires 2 arg(s)

[1] https://btrfs.wiki.kernel.org/#News
[2] http://article.gmane.org/gmane.comp.file-systems.btrfs/14173/match=read+only+snapshot
[3] http://blog.dailystuff.nl/2012/01/btrfs-and-readonly-snapshots/

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Jeff Strunk (jstrunk-math)]

I think this bug was reported on the wrong package.

[Jeff Strunk (jstrunk-math)]

https://launchpad.net/~yofel/+archive/btrfs has an up to date package for btrfs-tools with this functionality. The package in Precise appears to be a snapshot from June 2010.

# dpkg -i btrfs-tools_0.19+20120421-0daily6~bzr457~precise1_amd64.deb
(Reading database ... 108869 files and directories currently installed.)
Preparing to replace btrfs-tools 0.19+20100601-3ubuntu3 (using btrfs-tools_0.19+20120421-0daily6~bzr457~precise1_amd64.deb) ...
Unpacking replacement btrfs-tools ...
Setting up btrfs-tools (0.19+20120421-0daily6~bzr457~precise1) ...
Processing triggers for man-db ...
# btrfs subvolume snapshot -r /export/ftp /export/ftp/.snapshot/hardy
Create a readonly snapshot of '/export/ftp' in '/export/ftp/.snapshot/hardy'

[Stefan Lasiewski (stefanlasiewski)]

Just confirming that this also happens in Precise. I recently upgraded to Precise, and I get this same error.

$ cat /etc/issue
Ubuntu 12.04 LTS \n \l

$ btrfs subvolume snapshot -r /u1 /u1/.snapshot/test
ERROR: 'subvolume snapshot' requires 2 arg(s)