CentOS - Sep 2021 - Troubles expanding file system.

I realized I was still on receiving the daily digest format last night, so I
have probably screwed up the threading on this now.  If you cc me directly maybe
I can maintain the future threading.

Ok, looking at Parted it looks like the resize (or resizepart) command will be
what I will need.  But that doesn't appear to help recognize the expanded
disk, so I think I need something before that.  That is what I thought the echo
1 > rescan would do for me.

I will look more into fdisk to understand the capabilities there.  I am going to
take advantage of the holiday weekend in a few days to take care of this so I am
trying to understand all of the options available to me before diving into the
task.

In response to Gordon also, I did rescan the drive as suggested and got the same
results; no such file or directory.  So then I did a search for the rescan file
to see where it was present.  Found it in a few locations, but this one looks to
be the one that I would want to try.

/sys/devices/pci0000:00/0000:00:01.1/host1/target1:0:0/1:0:0:0/

The rescan file was also located in just:  /sys/bus/pci  but don't know if
that would do the job for the specific device.

Thanks for everyone's input.  Very helpful.  More suggestions are welcome
while I am still reading up on options.

Jeff



Date: Wed, 1 Sep 2021 13:15:37 -0400
From: Stephen John Smoogen<smooge at gmail.com>
To: CentOS mailing list<centos at centos.org>
Subject: Re: [CentOS] Troubles expanding file system.
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	<CANnLRdhhRkMagTcZ+eqALoteYcXD26nMrHzv7L9F1A35jGS=3g at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

On Wed, 1 Sept 2021 at 12:42, Jeff Boyce<jboyce at meridianenv.com> 
wrote:
> Greetings -
>
>       I have tried posting this four times now, from two different email
> addresses (on the 25th, 27th, 30th, and 31st) and it never appeared.  I
> don't see it in the archives, so it appears to be getting dropped in
> transition for some reason.  I am not getting messages from the email
> system saying it is undeliverable, or is bounced; I am sending as plain
> text, not HTML, I stripped off my signature.  If this makes it through,
> someone please give me a clue why the others might not have.  But that
> is not as important as the real issue that I am trying to get addressed
> below.  Thanks for any assistance.
>
>       I have a Dell PowerEdge server with a CentOS KVM host (Earth) with
> one CentOS guest (Sequoia) that I am trying to expand the partition and
> filesystem on.  I have LVM logical volumes on the host system (Earth),
> which are used as devices/partitions on the guest system (Sequoia).  In
> this particular situation I have successfully extended the logical
> volume (lv_SeqEco) on Earth from 500GB to 700GB.
>
> 1.  Checking the disk information (lsblk) on Earth shows that the
> logical volume (lv_SeqEco) is now listed as 700GB.
>
> 2.  Checking disk information (lsblk) on Sequoia shows that the disk
> /dev/vde is still listed as 500GB, and partition /dev/vde1 where the
> mount point /ecosystem is located is also listed as 500GB.
>
> 3.  I had tried using the resize2fs command to expand the filesystem on
> /dev/vde1, but it returned with the result that there was nothing to
> do.  Which makes sense now after I checked the disk information, since
> /dev/vde on Sequoia has not increased from 500GB to 700GB.
>
Thanks for the long list of items of what you have done. In Fedora
Infrastructure, we used this method to resize images in the past
https://pagure.io/infra-docs/blob/main/f/docs/sysadmin-guide/sops/guestdisk.rst

The guest system usually needs to have the `fdisk` , `gdisk` or
`parted` commands rerun to resize the disk to its new size.

> 4.  On previous occasions when I have done this task, I would just start
> GParted on Sequoia and use the GUI to expand the partition and
> filesystem.  A real quick and simple solution.
>
> 5.  The problem I have now is that the VGA adapter on my server has died
> and I have no graphical output to the attached monitor, nor to the iDrac
> console display.  So I am stuck doing this entirely by the command line
> while logged into the system remotely.
>
> 6.  I suspect that I need to rescan the devices on Sequoia so that it
> recognizes the increased space that has been allocated from the extended
> the logical volume.  But when I did that (command below) it came back
> with a no such file or directory.
>
> echo 1 > /sys/class/block/vde1/device/rescan
>
Not sure that would do anything.

> 7.  This server is being retired in the next few months, but I need this
> additional space prior to migrating to the new system. Can someone give
> me some guidance on what I am missing in this sequence?
>
> Let me know if I haven't been clear enough in the explanation of my
> systems and objective.  Thanks.

On Thu, Sep 2, 2021 at 7:16 PM Jeff Boyce <jboyce at meridianenv.com>
wrote:
>
> >
> > 6.  I suspect that I need to rescan the devices on Sequoia so that it
> > recognizes the increased space that has been allocated from the
extended
> > the logical volume.  But when I did that (command below) it came back
> > with a no such file or directory.
> >
> > echo 1 > /sys/class/block/vde1/device/rescan
> >
> Not sure that would do anything.
>
> https://lists.centos.org/mailman/listinfo/centos

What are the CentOS versions of your host and guest?
As far as I know, virtio disks have never supported rescan from inside the
guest and so there isn't the corresponding "rescan" special file.
I found this old, but interesting thread:
https://forum.proxmox.com/threads/extend-rescan-virtio-disk-in-guest-vm.7989/

Can you confirm your host libvirt version and your guest kernel are ok with
what is referred?
In case you could try with the qemu monitor command.

See also here for a reference of possible qemu monitor commands:
https://qemu-project.gitlab.io/qemu/interop/qemu-qmp-ref.html

And here for consideration regarding RH EL 6 host:
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/virtualization_administration_guide/sub-sect-domain_commands-using_blockresize_to_change_the_size_of_a_domain_path

Also here you find reference of command to issue, but somehow the syntax
changes depending on components' versions:
https://www.humblec.com/is-it-possible-to-do-online-resizing-of-guest-block-devices-or-without-shutdown/

HIH,
Gianluca

Hi Jeff,
> I realized I was still on receiving the daily digest format last night, so
> I have probably screwed up the threading on this now.  If you cc me
> directly maybe I can maintain the future threading.
>
> Ok, looking at Parted it looks like the resize (or resizepart) command
> will be what I will need.  But that doesn't appear to help recognize
the
> expanded disk, so I think I need something before that.  That is what I
> thought the echo 1 > rescan would do for me.
I'm not sure what your current state is but I'd like to point out what I
usually do to online resize disks on KVM hosts/guests.

After expanding the disk image/logical volume, let the quest know it has
changed. To do so, run like this on the host:

virsh blockresize db01 /var/lib/libvirt/images/db01.var.img 7516192768B

or

virsh blockresize db01 vdb 7516192768B

Note: I'm using bytes (B) as unit to make very sure it's correct!

After doing so, you should see that disk size has changed on the guest, in
syslog or with dmesg.

Now you can modify partition tables or pvresize. After that, resize the
fillesystems with resize2fs or xfs_growfs.

That's all possible while the guest is online with one exception outlined
below.

There is one thing that I couldn't find a solution for no matter what I
tried: When the root/boot disk of the guest is being resized, it's not
possible to modify and reread the new partition table without reboot.

Regards,
Simon