How to merge two or more disk partitions on Centos 7¶
I’ve been working with centos 7 virtual machine provisioned via VMware’s vrealize suite. One thing I particulary dislike is how the storage disk gets partitioned into tiny partititions during the VM provisioning:
$ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs 1.9G 8.9M 1.9G 1% /run
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-root 6.0G 70M 6.0G 2% /
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-usr 6.0G 1.5G 4.6G 24% /usr
/dev/sda1 1014M 232M 783M 23% /boot
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-data 61G 34M 61G 1% /data
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-usr_local 6.0G 33M 6.0G 1% /usr/local
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-home 10G 33M 10G 1% /home
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-var 6.0G 414M 5.6G 7% /var
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-tmp 2.0G 33M 2.0G 2% /tmp
tmpfs 379M 0 379M 0% /run/user/1001
Notice how var, data, home, tmp, usr, usr_local, and root have their own partitions. I prefer to have a few but large disk partitions. So, today I figured out how to merge two or more partitions into the root partition (thank you, @kmpaul for the help and documenting this!).
Step 1 — Make sure you are logged in as root¶
Step 2 — Backup data from the partitions you want to merge into the root partiton¶
$ rsync -a /home/ /home-old/
$ rsync -a /tmp/ /tmp-old/
$ rsync -a /var/ /var-old/
Step 3 — Reboot the VM into an emergency mode¶
$ systemctl emergency
Step 4 — Umount and remove logic volume for each of the partitions¶
$ umount /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-data
$ umount /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-home
$ umount /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-var
$ umount /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-tmp
$ lvremove /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-data
$ lvremove /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-home
$ lvremove /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-var
$ lvremove /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-tmp
Step 5 — Copy the backed up data¶
$ rsync -a /home-old/ /home/
$ rsync -a /var-old/ /var/
$ rsync -a /tmp-old/ /tmp/
Step 6 — Edit the /etc/fstab file by removing or commenting out the partitions we don’t need¶
$ vi /etc/fstab
Step 7 — Extend the root partition to fill the remaining space¶
$ lvextend -l +100%FREE -r /dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-root
Step 8 — Remove the backups¶
$ rm -rf /home-old/ /tmp-old/ /var-old/
Step 9 — Reboot the system¶
$ reboot
Step 10 — Login to the VM as a regular user or root¶
Let’s check that our / root partition size has increased:
$ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs 1.9G 8.9M 1.9G 1% /run
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-root 85G 474M 85G 1% /
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-usr 6.0G 1.5G 4.6G 24% /usr
/dev/sda1 1014M 232M 783M 23% /boot
/dev/mapper/centos_dhcp--zzz--zzz--zzz--zz-usr_local 6.0G 33M 6.0G 1% /usr/local
tmpfs 379M 0 379M 0% /run/user/1001
Voilà! 🙌