Each line of /etc/fstab contains the necessary settings to mount one partition, drive or network share. The line has six columns, separated by whitespaces or tabs. The columns are as follows:
- The device file, UUID or label or other means of locating the partition or data source.
- The mount point, where the data is to be attached to the filesystem.
- The filesystem type.
- Options, including if the filesystem should be mounted at boot.
- Adjusts the archiving schedule for the partition (used by app-arch/dump). 0 disables, 1 enables the feature.
- Controls the order in which fsck checks the device/partition for errors at boot time. The root device should be 1. Other partitions should be either 2 (to check after root) or 0 (to disable checking for that partition altogether).
An example for the root device:
/dev/sda1 / ext4 defaults 0 1
Special characters can be escaped by using their octal representation from an ASCII table. For example, if the name of the mount point contains spaces or tabs these can be escaped as \040 and \011 respectively.
For more detailed information see man 5 fstab.
UUIDs and labels
In the first column, a UUID can be used instead of a device file:
UUID=339df6e7-91a8-4cf9-a43f-7f7b3db533c6 / ext4 defaults 0 1
Alternatively, a LABEL can be used:
LABEL=Gentoo / ext4 defaults 0 1
Please read this for details on how to retrieve UUIDs and labels.
The following OpenRC services read the fstab to mount or manage the filesystems:
- localmount- Mount disks and swap according to fstab.
- netmount - Mount network shares according to fstab.
- fsck - Check and repair filesystems according to fstab.
- root - Mount the root filesystem read/write.
These services supplement the fstab, if the filesystems are not explicitly stated:
- sysfs - Mount the /sys filesystem.
- devfs - Mount system critical filesystems in /dev.
Check that they are enabled to start at boot time:
- Mounting partitions (Security Handbook)
- Disk Quotas (Security Handbook)
- removable media
- AutoFS — a program that uses the Linux kernel automounter to automatically mount filesystems on demand.
- fstab (AMD64 Handbook)