genfstab

This article or section is a candidate for merging with fstab#Tips and tricks.

Notes: There is not enough content for a separate article. The genfstab(8) man page provides everything besides the warnings and examples. (Discuss in Talk:Genfstab)

genfstab(8) is a Bash script that is used to automatically detect all mounts under a given mountpoint, its output can then be redirected into a file, usually /etc/fstab.

Installation

It is present by default on Arch installation media and can be installed as part of the arch-install-scripts package on an already installed system.

There is also a stand alone fork of this tool that can be used on other distributions, you can find it here.

Usage

You can get a list of your current mounts by using:

$ genfstab /

The script supports finding mounts by kernel descriptor, device/partition label or device/partition UUID. It will output kernel descriptor by default (kernel descriptor being /dev/xxx), you can use -L, -t PARTLABEL, -U or -t PARTUUID for file system label, GPT partition label, file system UUID or GPT partition UUID respectively.

Warning Kernel name descriptors for block devices are not persistent and can change each boot, they should not be used in configuration files (including /etc/fstab).

The more common usage scenario would be getting an fstab for a chroot, for this you would do something like the following:

# mount /dev/sda3 /mnt
# mount --mkdir /dev/sda1 /mnt/efi

$ genfstab -U /mnt

# /dev/sda3
UUID=185aebd2-ce76-47dd-baf4-5ad0a80fa963       /               ext4            rw,noatime      0 1

# /dev/sda1
UUID=E5C7-6DD7          /efi       vfat             rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro   0 2

In this case genfstab shows both mounts below the mountpoint /mnt and list them by device UUID.

Tip Notice we mounted the device sda3 into /mnt yet genfstab shows it as being the main root mountpoint /, this is because it treats the given mountpoint as the root mount.

Usually you would want to redirect the output to a file, this can be achieved with the following:

# genfstab -U /mnt >> /mnt/etc/fstab

Warning

Make sure you create a backup of your existing fstab before overwriting it.
Be mindful of where you are saving the fstab file, for example if you want to create it for a chroot then you do not want to overwrite the one on your main installation.