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-   -   is it possible to resive /var online? (http://www.linux-archive.org/centos/365073-possible-resive-var-online.html)

Brendan Minish 05-02-2010 08:32 PM

is it possible to resive /var online?
 
Rudi Ahlers wrote:
> Hi all,
>
> Is it possible, safely, to resize /var while a server is running? I
> urgently need to resize a full 2GB /var on a running server which is
> located at a remote location where no one can get to it for 2 days?
>
> The system runs on lvm.

Growing on line EXT3 file systems on LVM has always worked ok for me.
shrinking needs to be done off line but growing on line File systems has
not given me any trouble to date.

I expect that the likelihood of problems with this is proportional to
the distance from your current location to the server though ;-)

regards
Brendan
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Kwan Lowe 05-02-2010 08:35 PM

is it possible to resive /var online?
 
On Sun, May 2, 2010 at 3:15 PM, Rudi Ahlers <rudiahlers@gmail.com> wrote:
> Hi all,
>
> Is it possible, safely, to resize /var while a server is running? I urgently
> need to resize a full 2GB /var on a running server which is located at a
> remote location where no one can get to it for 2 days?
>
> The system runs on lvm.

If it's on LVM it's pretty simple:

lvs to show the current lvs.


lvresize -L +500M /dev/VolGroup00/var_lv
resize2fs /dev/VolGroup00/var_lv

If you're running earlier versions of lvm you may need to use
ex2online instead of resize2fs.
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Rudi Ahlers 05-02-2010 08:36 PM

is it possible to resive /var online?
 
On Sun, May 2, 2010 at 10:32 PM, Brendan Minish <bminish@minish.org> wrote:


Rudi Ahlers wrote:
> Hi all,
>
> Is it possible, safely, to resize /var while a server is running? I
> urgently need to resize a full 2GB /var on a running server which is
> located at a remote location where no one can get to it for 2 days?


>
> The system runs on lvm.

Growing on line EXT3 file systems on LVM has always worked ok for me.
shrinking needs to be done off line but growing on line File systems has
not given me any trouble to date.



I expect that the likelihood of problems with this is proportional to
the distance from your current location to the server though ;-)

regards
Brendan
_______________________________________________




*
*
Hi Brendan,
*
I've also safely grown LVM volumes online, but /var is a bit more trickey since a lot of stuff runs straight from it .So I don't want to attempt this if it's going to break the whole system.



--
Kind Regards
Rudi Ahlers
SoftDux

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com


Office: 087 805 9573
Cell: 082 554 7532

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Kwan Lowe 05-02-2010 08:44 PM

is it possible to resive /var online?
 
>
> I've also safely grown LVM volumes online, but /var is a bit more trickey
> since a lot of stuff runs straight from it .So I don't want to attempt this
> if it's going to break the whole system.

OK.. get you now..

The main thing to keep in mind is that you'll need a little bit of
free space in order to grow /var. I grow /var often on many systems.
There's also a possibility that you'll need to run tune2fs to grow the
journal to allow a larger maximum filesystem size. This cannot be done
with /var online though.
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Rudi Ahlers 05-02-2010 09:01 PM

is it possible to resive /var online?
 
On Sun, May 2, 2010 at 10:44 PM, Kwan Lowe <kwan.lowe@gmail.com> wrote:


>
> I've also safely grown LVM volumes online, but /var is a bit more trickey
> since a lot of stuff runs straight from it .So I don't want to attempt this
> if it's going to break the whole system.



OK.. get you now..

The main thing to keep in mind is that you'll need a little bit of
free space in order to grow /var. I grow /var often on many systems.
There's also a possibility that you'll need to run tune2fs to grow the


journal to allow a larger maximum filesystem size. This cannot be done
with /var online though.



_______________________________________________


*
heh, there's plenty space left on the drive:
*
[root@zaxen02 ~]# pvscan
* PV /dev/md1** VG LVM01** lvm2 [232.69 GB / 141.69 GB free]
* Total: 1 [232.69 GB] / in use: 1 [232.69 GB] / in no VG: 0 [0** ]

*
As far as I know, one needs to unmount a volume in order to resize it, but /var can't be unmounted.
*
I wonder if I could script something that could run in single user mode when it reboots,* but
1. how do I tell it to reboot in ginle user mode, via SSH?
2. how do I tell the server to login by itself, i.e. don't need someone to type in the root password @ the console, then check to make sure it's in single user mode?
*
From here could be as simple as unmouting /var, running lvresize +2GB /dev/LVM/var etc
*
*
*
Has anyone done anything like this before, with success? i.e. do you have a working procedure / script to share with me? I won't be able to test the process, if it fails then I'm stuck
*


--
Kind Regards
Rudi Ahlers
SoftDux

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com


Office: 087 805 9573
Cell: 082 554 7532

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Kwan Lowe 05-02-2010 09:13 PM

is it possible to resive /var online?
 
On Sun, May 2, 2010 at 5:01 PM, Rudi Ahlers <rudiahlers@gmail.com> wrote:

>
> heh, there's plenty space left on the drive:
>
> [root@zaxen02 ~]# pvscan
> * PV /dev/md1** VG LVM01** lvm2 [232.69 GB / 141.69 GB free]
> * Total: 1 [232.69 GB] / in use: 1 [232.69 GB] / in no VG: 0 [0** ]
>
> As far as I know, one needs to unmount a volume in order to resize it, but
> /var can't be unmounted.

With LVM you don't need to unmount /var. You can do it on a running
system with the following caveats:

1) You'll need some free space on /var. I.e., not extra space in the
volume group, but a little extra space in the /var partition itself.
In other words, don't try to resize a completely full /var partition.

2) There is a possibility that you'll need to resize some metadata. If
so, this has to be done offline via a boot disk for /var.
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Kahlil Hodgson 05-02-2010 09:23 PM

is it possible to resive /var online?
 
On 05/03/2010 05:15 AM, Rudi Ahlers wrote:
> Is it possible, safely, to resize /var while a server is running? I
> urgently need to resize a full 2GB /var on a running server which is
> located at a remote location where no one can get to it for 2 days?

I've done it before on a quiet system and it worked fine. Still think
its a bit risky if you cant get to it for 2 days.

> I already moved /var/logs to it's own LVM partition but it didn't help
> at all so I think it's better to rather just resize it. Google searches
> suggest taking the server offline, or boot into single mode. But this
> won't be possible for another 2 or so days and I urgently need to
> install more software on the server.

If you "urgently need to install new software", then a small possibility
of breaking the system for 2 days is probably a show stopper. I'd
continue with your approach (as a temporary solution) of migrating bits
of /var to a different LVM. If moving /var/logs didn't help, you need
to track down the big directories. Try

du -sh /var/*

then drill down though your big candidates

/var/cache/yum, /var/spool, and /var/tmp are always candidates for clean up.

Hope this helps.

Kal


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Rudi Ahlers 05-02-2010 09:28 PM

is it possible to resive /var online?
 
On Sun, May 2, 2010 at 11:13 PM, Kwan Lowe <kwan.lowe@gmail.com> wrote:


On Sun, May 2, 2010 at 5:01 PM, Rudi Ahlers <rudiahlers@gmail.com> wrote:

>
> heh, there's plenty space left on the drive:
>
> [root@zaxen02 ~]# pvscan


> * PV /dev/md1** VG LVM01** lvm2 [232.69 GB / 141.69 GB free]
> * Total: 1 [232.69 GB] / in use: 1 [232.69 GB] / in no VG: 0 [0** ]
>
> As far as I know, one needs to unmount a volume in order to resize it, but


> /var can't be unmounted.

With LVM you don't need to unmount /var. You can do it on a running
system with the following caveats:

1) You'll need some free space on /var. I.e., not extra space in the


volume group, but a little extra space in the /var partition itself.
In other words, don't try to resize a completely full /var partition.

2) There is a possibility that you'll need to resize some metadata. If


so, this has to be done offline via a boot disk for /var.



_______________________________________________

*
That's exactly as I thought :)
*
For now, a safer way around this, I moved the /var/lib/xend/saved folder to it's own LVM volume, and re-mounted it on /var/lib/xend.
*
So now /var has 1.4GB free space from 2GB
*
*
*
*


--
Kind Regards
Rudi Ahlers
SoftDux

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com


Office: 087 805 9573
Cell: 082 554 7532

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Brendan Minish 05-02-2010 09:29 PM

is it possible to resive /var online?
 
On Sun, 2010-05-02 at 23:01 +0200, Rudi Ahlers wrote:

--snip--

> Has anyone done anything like this before, with success? i.e. do you
> have a working procedure / script to share with me? I won't be able to
> test the process, if it fails then I'm stuck

yes, on line, with no issues on centos 5.4

just tested it again in a virtual machine, with no issues

root@dhcp-204 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
3.7G 1.3G 2.3G 37% /
/dev/mapper/VolGroup00-LogVol02
961M 43M 870M 5% /var
/dev/hda1 99M 13M 82M 14% /boot
tmpfs 250M 0 250M 0% /dev/shm
[root@dhcp-204 ~]# lvextend -L +1G /dev/VolGroup00/LogVol02
Extending logical volume LogVol02 to 1.97 GB
Logical volume LogVol02 successfully resized
[root@dhcp-204 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
3.7G 1.3G 2.3G 37% /
/dev/mapper/VolGroup00-LogVol02
961M 43M 870M 5% /var
/dev/hda1 99M 13M 82M 14% /boot
tmpfs 250M 0 250M 0% /dev/shm
[root@dhcp-204 ~]# resize2fs /dev/VolGroup00/LogVol02
resize2fs 1.39 (29-May-2006)
Filesystem at /dev/VolGroup00/LogVol02 is mounted on /var; on-line resizing required
Performing an on-line resize of /dev/VolGroup00/LogVol02 to 516096 (4k) blocks.
The filesystem on /dev/VolGroup00/LogVol02 is now 516096 blocks long.

[root@dhcp-204 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
3.7G 1.3G 2.3G 37% /
/dev/mapper/VolGroup00-LogVol02
2.0G 43M 1.8G 3% /var
/dev/hda1 99M 13M 82M 14% /boot
tmpfs 250M 0 250M 0% /dev/shm
[root@dhcp-204 ~]#



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JohnS 05-02-2010 11:12 PM

is it possible to resive /var online?
 
On Sun, 2010-05-02 at 17:13 -0400, Kwan Lowe wrote:
> On Sun, May 2, 2010 at 5:01 PM, Rudi Ahlers <rudiahlers@gmail.com> wrote:
>
> >
> > heh, there's plenty space left on the drive:
> >
> > [root@zaxen02 ~]# pvscan
> > PV /dev/md1 VG LVM01 lvm2 [232.69 GB / 141.69 GB free]
> > Total: 1 [232.69 GB] / in use: 1 [232.69 GB] / in no VG: 0 [0 ]
> >
> > As far as I know, one needs to unmount a volume in order to resize it, but
> > /var can't be unmounted.
>
> With LVM you don't need to unmount /var. You can do it on a running
> system with the following caveats:
>
> 1) You'll need some free space on /var. I.e., not extra space in the
> volume group, but a little extra space in the /var partition itself.
> In other words, don't try to resize a completely full /var partition.
>
> 2) There is a possibility that you'll need to resize some metadata. If
> so, this has to be done offline via a boot disk for /var.
---
Sounds good but I really do wonder if he has a hardware raid controller
that does not support resizing of Linux LVM on top of the HW Raid Volume
Set?? No one asked that part.

John

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