Scope: Block devices, partitions, filesystems, mounts, fstab, and swap on Debian-based and RHEL-based distributions
Topics: lsblk, blkid, parted, GPT, mkfs.ext4, mkfs.xfs, mount, fstab, swap.

1. Inspect Block Devices#

Identify every block device before touching it:

lsblk
lsblk -f

Expected output (example):

NAME   FSTYPE LABEL UUID                                 MOUNTPOINT
sda
├─sda1 ext4         1a2b3c4d-0000-0000-0000-000000000000 /
└─sda2 swap         5e6f7a8b-0000-0000-0000-000000000000 [SWAP]
sdb
└─sdb1 ext4         9c8d7e6f-0000-0000-0000-000000000000 /srv/data

Options:

• lsblk: Lists devices, sizes, types, and mount points.
• -f: Adds filesystem type, label, and UUID.

2. Read Device Attributes with blkid#

Inspect the usage:

blkid /dev/<DEVICE>
blkid /dev/<DEVICE>1

Expected output (example):

/dev/sdb1: LABEL="data" UUID="9c8d7e6f-0000-0000-0000-000000000000" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="..."

Use blkid to obtain UUIDs for /etc/fstab. Run it as root to see all devices.

3. Create a GPT Partition Table#

Warning: this destroys all data on the device. Verify the device name with lsblk first.

Run as root:

parted /dev/<DEVICE> mklabel gpt
parted /dev/<DEVICE> mkpart primary ext4 1MiB 100%
parted /dev/<DEVICE> print

Options:

• mklabel gpt: Writes a new GPT partition table.
• mkpart primary ext4 1MiB 100%: Creates one partition from 1 MiB to the end of the device. The 1 MiB offset keeps the partition aligned.
• print: Displays the resulting layout.

Reload the partition table in the kernel:

partprobe /dev/<DEVICE>
udevadm settle

Verify the result:

lsblk /dev/<DEVICE>

Note on partition names: SATA disks use <DEVICE>1 (for example /dev/sdb → /dev/sdb1), while NVMe and loop devices insert p (for example /dev/nvme0n1 → /dev/nvme0n1p1).

4. Create a Filesystem#

For ext4 (default on Debian-based systems):

mkfs.ext4 -L <LABEL> /dev/<DEVICE>1

For XFS (default on RHEL-based systems):

mkfs.xfs -L <LABEL> /dev/<DEVICE>1

Options:

• -L <LABEL>: Sets a filesystem label.
• mkfs.xfs -f: Required to overwrite an existing XFS signature.

mkfs destroys existing data on the target. Double-check the device before running it. See Part 1 and Part 2 for distribution-specific choices.

5. Mount and Unmount#

Create the mount point and mount the filesystem:

mkdir -p <MOUNT_POINT>
mount /dev/<DEVICE>1 <MOUNT_POINT>
findmnt <MOUNT_POINT>

Unmount it:

umount <MOUNT_POINT>

If umount reports target is busy, processes are still using the filesystem. Identify them:

fuser -vm <MOUNT_POINT>

Close the listed processes before unmounting. Use umount -l only when a lazy unmount is acceptable.

6. Persist the Mount in /etc/fstab#

Register the filesystem by UUID. Example entry in /etc/fstab:

UUID=<UUID>  <MOUNT_POINT>  ext4  defaults  0  2

Obtain the UUID from blkid /dev/<DEVICE>1 or lsblk -f.

Test the configuration without rebooting:

mount -a

Expected output: none. Fix any error before the next boot. Verify the result:

findmnt <MOUNT_POINT>

7. Add Swap#

Create swap on a partition or logical volume:

mkswap /dev/<DEVICE>2
swapon /dev/<DEVICE>2
swapon --show

Expected output (example):

NAME      TYPE      SIZE USED PRIO
/dev/sdb2 partition   4G   0B   -2

Persist it in /etc/fstab:

UUID=<SWAP_UUID>  none  swap  sw  0  0

Deactivate swap:

swapoff /dev/<DEVICE>2

Options:

• mkswap: Writes a swap signature. Destroys existing data on the target.
• swapon: Activates the swap area.
• swapoff: Deactivates swap. Requires enough free RAM to move swapped pages back.

Part 1: Debian-Based Systems#

Examples: Debian, Ubuntu

1. Install the Tools#

Run as root:

apt update
apt install parted e2fsprogs

2. Use ext4 as the Default Filesystem#

Format the partition:

mkfs.ext4 -L <LABEL> /dev/<DEVICE>1

Check the filesystem while unmounted:

e2fsck -f /dev/<DEVICE>1

3. Grow the Filesystem Online#

After extending the underlying partition or volume, grow ext4 while mounted:

resize2fs /dev/<DEVICE>1

ext4 can also be shrunk offline after unmounting and running e2fsck -f, but shrinking is risky and rarely needed. Take a backup first.

Part 2: RHEL-Based Systems#

Examples: RHEL, Rocky Linux, AlmaLinux

1. Install the Tools#

Run as root:

dnf install parted xfsprogs

2. Use XFS as the Default Filesystem#

Format the partition:

mkfs.xfs -L <LABEL> /dev/<DEVICE>1

Check the filesystem while unmounted:

xfs_repair -n /dev/<DEVICE>1

3. Grow the Filesystem Online#

After extending the underlying partition or volume, grow XFS from its mount point while mounted:

xfs_growfs <MOUNT_POINT>

XFS cannot be shrunk. Size the filesystem conservatively and grow it later. Inspect the layout with:

xfs_info <MOUNT_POINT>

Part 3: Important Notes#

fstab Fields#

Filesystem Comparison#

Security Guidelines#

• Double-check the device name with lsblk before running mkfs. mkfs on the wrong device destroys data irrecoverably.
• Prefer UUIDs in /etc/fstab. Device names such as /dev/sdb1 can change between boots.
• Never edit /etc/fstab without testing the result with mount -a. A broken entry can leave the system in emergency mode at boot.
• Run fsck or xfs_repair only on unmounted filesystems unless the tool documents online checks.
• Use noexec,nosuid,nodev on mounts holding untrusted or shared data.
• Do not store sensitive data on world-readable mount points; restrict directory permissions after mounting.
• Keep swap on a device separate from the root filesystem where possible, and remember that swap contents are unencrypted by default.
• In scripts, refuse to proceed when the target already contains a filesystem signature unless overwrite is intended.