After a recent move from Wheezy to Jessie, the root partition was looking a little full – to the point where the GUI wasn’t working due to a lack of /tmp space. So needed to take care of that while troubleshooting other issues.
# df -h Filesystem Size Used Avail Use% Mounted on /dev/dm-0 9.1G 8.4G 176M 99% / udev 10M 0 10M 0% /dev tmpfs 402M 6.5M 396M 2% /run tmpfs 1005M 68K 1005M 1% /dev/shm tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 1005M 0 1005M 0% /sys/fs/cgroup /dev/mapper/thor-home 904G 511G 347G 60% /home /dev/sde1 228M 47M 170M 22% /boot tmpfs 201M 0 201M 0% /run/user/1024 tmpfs 201M 8.0K 201M 1% /run/user/1000
Given that there is plenty of room on the /home partition and it’s all built on LVM, reallocating space from one to the other is fairly straightforward.
While you can grow an EXT4 filesystem while it is mounted, you can’t shrink one – and given that /home is constantly in use it was easier just to reboot into maintenance mode and take care of things that way.
# Unmount the home partition umount /mnt/home # Check the filesystem to make sure it is clean e2fsck -F /dev/mapper/thor-home # Shrink the filesystem to the desired size - in this case I'm reducing it to 880G resize2fs -p /dev/mapper/thor-home 880G # Shrink the logical volume to match lvreduce -L 880G /dev/mapper/thor-home # Check the file system again. If there are problems because the partition is too small, we # can still recover by using lvextend until it succeeds e.g. lvextend -L +1G /dev/mapper/thor-home e2fsck -F /dev/mapper/thor-home
That was the dangerous part. Extending the root filesystem to use the newly freed space is quite simple, but this time we are first growing the logical volume, then expanding the filesystem
# Extend the logical volume to use all the free space lvextend -l +100%FREE /dev/mapper/thor-root # Expand the filesystem resize2fs -p /dev/mapper/thor-root
At this point a scan of the filesystem is a good idea, but unfortunately we can’t do that to a mounted filesystem, so instead we can trigger the check on reboot
touch /forcefsck
But in the meantime we can see that the root partition now has plenty of space
# df -h Filesystem Size Used Avail Use% Mounted on /dev/dm-0 47G 8.8G 36G 20% / udev 10M 0 10M 0% /dev tmpfs 402M 6.5M 396M 2% /run tmpfs 1005M 68K 1005M 1% /dev/shm tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 1005M 0 1005M 0% /sys/fs/cgroup /dev/mapper/thor-home 867G 506G 317G 62% /home /dev/sdb1 228M 47M 170M 22% /boot tmpfs 201M 0 201M 0% /run/user/1024 tmpfs 201M 4.0K 201M 1% /run/user/1000
