linuxexpert-practice-labs/labs/lfcs/3-1-lvm/README.md

LFCS 3.1: LVM

Building a volume group, growing a logical volume while it's in use, snapshots, swapping out a disk, and shrinking ext4.

Before you start

The lab adds three empty 2 GiB spare disks: /dev/loop40, /dev/loop41 and /dev/loop42. They come back at every boot, before filesystems are mounted, so /etc/fstab lines and volume groups on them keep working.

Tasks

1. Create volume group vg_lab from /dev/loop40 and /dev/loop41, and a 1 GiB logical volume lv_data in it with an XFS filesystem, mounted at /data at every boot.
2. Grow lv_data and its filesystem by 500 MiB while it's mounted.
3. Write version 1 to /data/notes.txt. Snapshot lv_data as lv_data_snap (200 MiB is plenty), then change /data/notes.txt to version 2 and read the old version from the snapshot (mount it read-only at /mnt/snap). Keep the snapshot.
4. Add the third disk, /dev/loop42, to vg_lab, then remove the first disk, /dev/loop40, from it without losing data.
5. Create a 1 GiB logical volume lv_files in vg_lab with an ext4 filesystem, mounted at /files at every boot. Copy /etc/services into it, then shrink the volume and its filesystem to 600 MiB.

Hints

• pvcreate, vgcreate, lvcreate -n -L, mkfs.xfs, a line in /etc/fstab, then systemctl daemon-reload and mount -a.
• lvextend -r; df -h /data before and after.
• lvcreate -s; an XFS snapshot needs mount -o ro,nouuid.
• vgextend, pvmove, vgreduce, pvremove; pvs and lvs -o +devices.
• ext4 shrinks only unmounted: umount, then lvreduce -r.