fstab

Getting Started

What /etc/fstab Does

/etc/fstab defines filesystems and swap areas that should be mounted automatically.

Each entry is processed at boot and can also be applied manually later.

Edit fstab

sudoedit /etc/fstab

Back Up Before Changes

sudo cp /etc/fstab /etc/fstab.bak.$(date +%F-%H%M%S)

Validate Syntax

findmnt --verify --verbose

Apply New Mount Entries

sudo mount -a

Apply Swap Entries

sudo swapon -a

Entry Format

Generic Layout

[source] [mount_point] [filesystem] [options] [dump] [pass]

Field Meanings

Common pass Values

Identify Filesystems Safely

UUIDs and labels are more stable than /dev/sdX names.

Show UUIDs

blkid

Show Filesystems and Mountpoints

lsblk -f

Show Current Mount Tree

findmnt

Common Local Filesystem Entries

ext4 Partition by UUID

Use this as the default pattern for most local data partitions.

UUID=[uuid] [mount_point] ext4 defaults 0 2

XFS Partition by UUID

Use 0 0 because XFS is not checked by fsck in the same way as ext filesystems.

UUID=[uuid] /srv/data xfs defaults 0 0

EFI System Partition

This is the common Linux EFI entry.

UUID=[uuid] /boot/efi vfat umask=0077 0 1

Read-Only Archive Mount

Useful for snapshots, archives, or forensic copies.

UUID=[uuid] /srv/archive ext4 ro,nodev,nosuid,noexec 0 2

On-Demand Backup Disk

Use noauto to prevent mounting at boot and nofail to avoid boot delays if the disk is absent.

UUID=[uuid] /mnt/backup ext4 noauto,nofail,x-systemd.automount 0 2

Swap Entries

Swap Partition by UUID

This is the standard swap partition entry.

UUID=[uuid] none swap sw 0 0

Swap File

Use this for systems configured with a swap file instead of a dedicated partition.

/swapfile none swap sw 0 0

High-Priority Swap Device

Higher pri values are used first.

UUID=[uuid] none swap defaults,pri=100 0 0

Encrypted Swap Mapper

This is common when the swap device is unlocked through /etc/crypttab.

/dev/mapper/cryptswap none swap defaults 0 0

Encrypted Partitions

For LUKS devices, define the unlock step in /etc/crypttab, then reference the mapper device in /etc/fstab.

crypttab Entry for a LUKS Volume

[mapper_name] UUID=[uuid] none luks

Mount Unlocked LUKS Volume

After unlock, the device appears under /dev/mapper/.

/dev/mapper/[mapper_name] /secure ext4 defaults 0 2

LUKS Volume with Hardened Mount Options

Useful for data partitions that should not allow device files or setuid binaries.

/dev/mapper/[mapper_name] /srv/secure xfs defaults,nodev,nosuid 0 0

Encrypted Logical Volume from LVM

This is common when LVM provides the logical volume and the mapper path is mounted directly.

/dev/mapper/vg0-data /data ext4 defaults 0 2

NFS and NFSv4 Mounts

Use _netdev for network filesystems so systemd waits for networking.

Use nofail when the system should still boot even if the server is unavailable.

Generic NFS Mount

This is a good baseline for a reliable NFS mount.

[server]:[export_path] /mnt/nfs nfs rw,hard,_netdev 0 0

NFS Mount with Explicit Version

Use this when the server supports NFSv4 but you prefer the nfs filesystem type.

[server]:[export_path] /srv/share nfs rw,vers=4.1,hard,_netdev 0 0

Native NFSv4 Mount

This is the direct nfs4 form.

[server]:[export_path] /mnt/nfs4 nfs4 rw,hard,timeo=600,retrans=2,_netdev 0 0

NFSv4 Automount

x-systemd.automount delays the actual mount until first access.

[server]:[export_path] /srv/projects nfs4 rw,hard,noatime,_netdev,x-systemd.automount,x-systemd.idle-timeout=600 0 0

Read-Only NFSv4 Share

Useful for published content, package mirrors, or report exports.

[server]:[export_path] /mnt/reports nfs4 ro,hard,_netdev,nofail 0 0

NFS Home Directories

This pattern is common in labs and shared Linux environments.

[server]:/home /home nfs4 rw,hard,intr,_netdev 0 0

Slow or Optional NFS Server

Reduce boot impact when the share is not critical.

[server]:[export_path] /mnt/optional nfs nofail,_netdev,x-systemd.device-timeout=10s 0 0

Advanced Examples

Bind Mount

Expose one directory tree at another path.

/var/log /srv/chroot/log none bind 0 0

tmpfs for /tmp

Keep temporary files in memory with a size cap.

tmpfs /tmp tmpfs defaults,noatime,mode=1777,size=2G 0 0

Removable Media Mounted by Regular User

Use this for local lab machines or workstations.

UUID=[uuid] /mnt/usb ext4 noauto,user,nofail 0 0

Read-Only ISO Mount

Useful for loop-mounted installation media or appliance images.

/srv/images/debian.iso /mnt/iso iso9660 loop,ro 0 0

Mount by Label

Labels can be easier to recognize than UUIDs in small environments.

LABEL=media /srv/media ext4 defaults 0 2

Useful Mount Options

Testing and Troubleshooting

Mount Everything from fstab

sudo mount -av

Mount One Entry by Mountpoint

sudo mount [mount_point]

Unmount One Entry

sudo umount [mount_point]

Check Active Swap Devices

swapon --show

Check Generated Mounts

findmnt --fstab

Inspect Boot-Time Mount Errors

journalctl -b -p warning

Regenerate systemd Mount Units After Changes

sudo systemctl daemon-reload

Best Practices

Use UUID= or LABEL= instead of raw /dev/sdX names whenever possible.

Use 0 2 for most local ext filesystems and 0 0 for network filesystems, swap, and XFS.

Use _netdev for NFS and other network-backed mounts.

Use nofail for removable disks, optional NAS shares, and anything that should not block boot.

Test with findmnt --verify --verbose and mount -a before rebooting.