By default, most Linux Installers create separate /home partition, occupying most of the drive space, this article will describe How To increase root partition by reducing /home.
When server is used mostly for system services, you may transfer free space from /home partition to root partition.
Before adjustment we have root 12G partition and 43G free space on /home, which we would like to use:
Filesystem Type Size Used Avail Use% Mounted on udev devtmpfs 1.1G 0 1.1G 0% /dev tmpfs tmpfs 208M 508k 208M 1% /run /dev/mapper/devninja--vg-root ext4 12G 1.9G 9.5G 17% / tmpfs tmpfs 1.1G 0 1.1G 0% /dev/shm tmpfs tmpfs 5.3M 0 5.3M 0% /run/lock /dev/vda1 ext2 493M 89M 379M 19% /boot /dev/mapper/devninja--vg-home ext4 45G 689k 43G 1% /home /dev/mapper/devninja--vg-tmp ext4 791M 46k 734M 1% /tmp /dev/mapper/devninja--vg-var ext4 4.3G 544M 3.5G 14% /var tmpfs tmpfs 208M 0 208M 0% /run/user/1000
Umount home partition
First step is to unmount /home partition with command
umount /home
Shrink old /home
Shrink old /home partition to 20GB, (system will force you to check filesystem for errors by running e2fsck)
e2fsck -f /dev/mapper/devninja--vg-home # or using fsck -f /dev/mapper/devninja--vg-home resize2fs /dev/mapper/devninja--vg-home 33G
Reduce the LVM
lvreduce -L -33G /dev/mapper/devninja--vg-home
Extend /root LVM to new size
Extend /root LVM to new size, utilizing 100% of free space on disk
lvextend -l +100%FREE /dev/mapper/devninja--vg-root
Increase root partition
Grow /root (ext3/4) partition to new LVM size
lvextend -l +100%FREE /dev/mapper/devninja--vg-root
Mount /home
mount /home
Result
Filesystem Type Size Used Avail Use% Mounted on udev devtmpfs 1.1G 0 1.1G 0% /dev tmpfs tmpfs 208M 508k 208M 1% /run /dev/mapper/devninja--vg-root ext4 47G 2.0G 43G 5% / tmpfs tmpfs 1.1G 0 1.1G 0% /dev/shm tmpfs tmpfs 5.3M 0 5.3M 0% /run/lock /dev/vda1 ext2 493M 89M 379M 19% /boot /dev/mapper/devninja--vg-tmp ext4 791M 46k 734M 1% /tmp /dev/mapper/devninja--vg-var ext4 4.3G 544M 3.5G 14% /var tmpfs tmpfs 208M 0 208M 0% /run/user/0 /dev/mapper/devninja--vg-home ext4 9.6G 39M 9.1G 1% /home
After these simple steps we have 95% of free disk space of root partition.
