On 24.2.2012 21:05, Jeff Boyce wrote: > Greetings - > > I am going through some testing steps to expand a logical volume and the > corresponding filesystem on a KVM guest and have run across a deficiency in > my knowledge. I spent the afternoon yesterday googling for answers, but had > have come up blank still. What I am trying to do is resize the file system > to use the additional disk space that I added to the logical volume that the > guest uses. Here is what I have done and the details of my system. > > 0. Both my host and guest are running Centos 6.2. > > 1. My KVM host system has the LVM volume group that is divided into logical > volumes which are then presented to the KVM guests as raw space. > > 2. A guest may use 2 or 3 logical volumes from the host system for its > filesystem (/, /var, /data) and I have logical volumes named within the host > system by guest and mount point so that I know what each logical volume is > assigned to by it's name. > > 3. I expanded a specific logical volume on the host (/dev/vg/lv_guest1root) > that is used by Guest1, and I can see in vgdisplay and lvdisplay that the > logical volume was properly expanded. > > 4. I then issued a resize2fs /dev/vg/lv_guest1root command (on the host) > to resize the filesystem to the expanded logical volume. This resulted in a > message that it essentially couldn't find a valid filesystem superblock. > Well of course then I realized that there is no filesystem on the logical > volume from the perspective of the host. The filesystem wasn't set on the > logical volume until the guest installation occurred. > > 5. So then I switched over to the guest system and ran df -h to see the > existing filesystem > > [root@guest1 jeffb]# df -h > Filesystem Size Used Avail Use% Mounted on > /dev/vda2 4.5G 2.3G 2.0G 53% / > tmpfs 1004M 88K 1004M 1% /dev/shm > /dev/vda1 485M 30M 430M 7% /boot > /dev/vdb1 2.0G 219M 1.7G 12% /var > > 6. Then I ran resize2fs /dev/vda2 and got the result that the filesystem > is already xx blocks long. Nothing to do! > > So here is where I am stuck. Guest1 is my test system so it only has the / > and /var logical volumes, whereas the production guest (guest2) that I will > be expanding also has /data, which will be the logical volume that I will > expand. So two things I did not do where, I did not shut down the guest VM, > and I did not unmount the filesystem before asking it to resize. However my > research before doing this did not seem to indicate that I had to do either, > and the message about nothing to do also seems to indicate that they were > not necessary. > > So I am missing a hole in my knowledge and additional googling has not > helped to fill it. I must be missing something simple. Is this result due > to the fact that I am testing on expanding the / filesystem, and it would > work properly on a guest system that had /data? Do I need to unmount the > filesystem, or shut down the guest VM, or mount the guest from a LiveCD? I think you must reboot the guest to see the new bigger disk, then you can repartition, and then after another reboot you can resize your fs. -- Kind Regards, Markus Falb
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