Storage

Disk and memory

df -h
df -i
du -xh -d 1 / | sort -h
lsblk -f
free -h

df -h is free space by filesystem. df -i is free inodes. A disk that is out of inodes looks full while df -h still shows free space, which happens when something has created millions of tiny files. du -xh -d 1 / is the size of each top-level directory, staying on one filesystem, and sort -h orders the human-readable sizes. lsblk -f adds filesystem type and UUID, which is what you copy into /etc/fstab. free -h is memory; the available column is the one that answers “can this box take more work?”

Storage, LVM, and mounts

lsblk -f is the map of disks, filesystems, and UUIDs. parted below destroys what is already on /dev/sdb.

RHEL 9 and 10, and any GPT disk. The partition needs a name. mkpart does not format anything. mkfs.xfs does.

lsblk -f
sudo parted --script /dev/sdb mklabel gpt mkpart data xfs 1MiB 100%
sudo udevadm settle

Older hosts, and any MBR disk. primary is the MBR partition type. RHEL’s parted rejects it as the type on GPT, on RHEL 7, 8, and 9 alike. Use it only after mklabel msdos.

sudo parted --script /dev/sdb mklabel msdos mkpart primary xfs 1MiB 10GiB
sudo udevadm settle

sudo pvcreate /dev/sdb1
sudo vgcreate vgdata /dev/sdb1
sudo lvcreate -n lvapp -L 5G vgdata
sudo mkfs.xfs /dev/vgdata/lvapp
sudo blkid /dev/vgdata/lvapp

udevadm settle waits until /dev/sdb1 exists. A whole disk can be a physical volume with pvcreate /dev/sdb when you do not need a partition table. RHEL’s LVM guide uses that form.

Paste this into /etc/fstab. It is a file line, not a shell command. The UUID comes from blkid. The last two fields are dump and fsck pass. XFS uses 0 0.

UUID=11111111-2222-3333-4444-555555555555 /app xfs defaults 0 0

sudo systemctl daemon-reload
sudo findmnt --verify --verbose
sudo mount -a
sudo lvextend -r -L +2G /dev/vgdata/lvapp

daemon-reload rebuilds the mount units from fstab. On RHEL 8, 9, and 10, findmnt --verify checks the file before a reboot. The RHEL 7 storage guide does not document that flag. Use sudo mount -fav there: -f fakes the mount, -a reads fstab, -v prints what it would do. mount -a mounts what is not mounted yet. lvextend -r grows the logical volume and the filesystem together. +2G adds two gigabytes. Without the plus sign, -L 2G sets the size to two gigabytes. XFS can grow only while it is mounted, which lvextend -r requires.

Swap is a logical volume plus an fstab line. swapon -a enables only the swap devices listed in fstab, so the device has to be turned on by path until that line exists.

sudo lvcreate -n lvswap -L 2G vgdata
sudo mkswap /dev/vgdata/lvswap
sudo swapon /dev/vgdata/lvswap

The matching /etc/fstab line, after you replace the UUID from blkid:

UUID=11111111-2222-3333-4444-555555555555 none swap defaults 0 0

NFS needs nfs-utils. _netdev tells boot to wait until the network is up.

sudo dnf install -y nfs-utils
sudo mount -t nfs nfs01:/exports/share /mnt/share

The matching /etc/fstab line:

nfs01:/exports/share /mnt/share nfs defaults,_netdev 0 0

XFS grows and never shrinks. A bad fstab line drops the host into emergency mode on the next boot. On RHEL 8, 9, and 10 run findmnt --verify first. On RHEL 7 run mount -fav.