On Jun 23, 2013, at 4:24 PM, Eric Sandeen wrote:
> On 6/23/13 5:55 PM, Dave Chinner wrote:
>> On Fri, Jun 21, 2013 at 10:30:31PM -0700, aurfalien wrote:
>>> Hi all,
>>>
>>> So I have an XFS file system within LVM which has an external log.
>>>
>>> My mount option in FSTAB is;
>>>
>>> /dev/vg_spock_data/lv_data /data xfs logdev=/dev/sdc1,nobarrier,logbufs=8,noatime,nodiratime 1 1
>>>
>>> All is well no issues and very fast.
>>>
>>> Now I'd like to snapshot this bad boy and then run rsnapshot to create a few days backup.
>>
>> You need to snapshot the log device as well.
>>
>> But that is problematic in that you need to snapshot it at the same
>> time you snapshot the data volume. Hence yo'd have to do:
>>
>> # xfs_freeze -f <filesystem>
>> # <snapshot data volume>
>> # <snapshot log volume>
>> # xfs_freeze -u <filesystem>
>>
>> And now you can mount the snapshot with:
>>
>> # mount /dev/vg_spock_data/datasnapshot /snapshot -o nouuid,ro,logdev=/dev/vg_spock_log/logsnapshot
>>
>> If you can't snapshot the log device, then you can't snapshot the
>> filesystem. Yet another reason for using internal logs...
>
> Hm, given that freezing the fs makes the log (almost) completely clean, I wonder
> if he could mount with /dev/zero (or a loopback 0-filled file) to get at the snapshot,
> especially since it's being mounted RO.
>
> Should be safe & consistent, no?
>
> i.e.
>
> truncate --size=2g logfile (or however big it needs to be)
> losetup /dev/loop0 logfile
> mount /dev/vg_anette_data/datasnapshot /snapshot -o logdev=/dev/loop0,nouuid,ro
>
> -Eric
>
It worked!
After running your mount command above I get;
mount: you didn't specify a filesystem type for /dev/mapper/vg_anette_data-datasnapshot
I will try type xfs
/dev/mapper/vg_anette_data-datasnapshot on /snapshot type xfs (ro,logdev=/dev/loop0,nouuid)
mount: /snapshot does not contain SELinux labels.
You just mounted an file system that supports labels which does not
contain labels, onto an SELinux box. It is likely that confined
applications will generate AVC messages and not be allowed access to
this file system. For more details see restorecon(8) and mount(8).
And the contents of the /snapshot dir matched the data volume files, size, etc...
Wow, how cool are you man, many thanks!!!!
I'm thinking of disabling selinux on this box at any rate which should remove the above message.
- aurf
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