Storage: partitions and LVM

Goal

The typical exam scenario: "add a disk, create a 2 GB LV, mount it on /data persistently, then extend it to 3 GB."

The LVM chain

lsblk
pvcreate /dev/vdb
vgcreate vg_data /dev/vdb
lvcreate -L 2G -n lv_data vg_data
mkfs.xfs /dev/vg_data/lv_data
mkdir -p /data
mount /dev/vg_data/lv_data /data

Persistence: /etc/fstab

/dev/vg_data/lv_data  /data  xfs  defaults  0 0

Always check with mount -a before rebooting: a bad fstab can prevent boot (you end up in rescue).

Robust alternative: UUID=$(blkid -s UUID -o value /dev/vg_data/lv_data) then UUID=... /data xfs defaults 0 0.

Grow online

lvextend -L 3G /dev/vg_data/lv_data
xfs_growfs /data          # XFS grows while mounted
# ext4 instead: resize2fs /dev/vg_data/lv_data

Shrinking

XFS cannot shrink. To shrink an ext4 LV: umount, e2fsck -f, resize2fs (filesystem first), then lvreduce.

Verify

lsblk -f; df -h /data; vgs; lvs
findmnt /data