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 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.