[CentOS] How to move /var to another partition

Sun Sep 25 21:51:53 UTC 2016
J Martin Rushton <martinrushton56 at btinternet.com>

On 25/09/16 20:56, Robert Nichols wrote:
> On 09/25/2016 12:23 PM, J Martin Rushton wrote:
>> On 25/09/16 18:03, Robert Nichols wrote:
>>> On 09/25/2016 11:47 AM, TE Dukes wrote:
>>>> Hello,
>>>> I am getting low on space in my /(root) partition. I have 23GB free.
>>>> I have 350GB in my /home partition. I am the only user.
>>>> I was experimenting with virtualization and it causes the root
>>>> partition to
>>>> get very low. I would like to move /var from the root partition, to
>>>> the same
>>>> partition as /home, if that's safe to do.
>>>> Or, resize /home and add another partition for /var
>>>> I also don't want to screw the pooch doing it.
>>>> This is over my head. The more I read about it, the more confused I
>>>> get.
>>> The way I've been doing it for quite some time is to make /var a
>>> separate partition, put the home directories on /var/home, and then
>>> bind-mount /var/home on /home. In /etc/fstab that's:
>>>     /var/home   /home   none   bind   0 0
>>> To keep SELinux happy, you need to set up an equivalence of /var/home
>>> to /home:
>>>     semanage fcontext -a -e /home /var/home
>>> It's all completely transparent in the running system. The only time I
>>> have to remember that it's set up that way is when I'm looking in my
>>> backups and need to know that home directories are backed up as part
>>> of /var.
>> Alternatively create /home/VM and keep the virtualised disks in there.
> What I do is have a separate logical volume for /var/lib/libvirt,
> with /var/lib/libvirt/etc bind-mounted to /etc/libvirt. It keeps
> all the libvirt stuff together, since the backup requirements
> there are quite different from the rest of the system.
Good point that I should have mentioned earlier.  Remember that if
_anything_ in the VM changes (such as a log entry), then the host system
will see the virtual disk as changed and back the whole thing up.  You
can end up backing up 20 GiB per day just to accommodate a few KiB
change in the VM.

A lot depends on how you do your backups, but I set things so that if
the VM is running at backup time _it_ backs up its disks, not the host.

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