Fstab

Structure

Values are separated by one or more spaces.

Name	Value
Filesystem	The Filesystem / Partition to be mounted. Can be a the path to a partition e.g. /dev/sdb2 or a UUID e.g. PARTUUID=65561b67-2aee-4c48-8a67-2ea71f5f4ba
Mount Point	Path to the mountpoint. Should be an existing empty folder. Value none can be used for Swap-Partitions
FS-Type	Type of the file system e.g ext4 or ntfs
Options	Mounting options. e.g. defaults,nofail -> Default settings, allow booting when mounting the partition fails
Dump	Weather to create a Dump before mounting. 0 don't create dump. 1 create dump
Check Fsck	Check file system before mounting them. 0 don't check anything should be used for Windows / NTFS Partitions. 1 For root file system (Except if type is btfsor XFS). 2 Check the filesystem before mounting.

Example fstab file:

# This is the default fstab of a rpi with an external harddrive
proc            /proc           proc    defaults          0       0
PARTUUID=0a70b801-01  /boot           vfat    defaults,flush    0       2
PARTUUID=0a70b801-02  /               ext4    defaults,noatime  0       1
# a swapfile is not a swap partition, no line here
#   use  dphys-swapfile swap[on|off]  for that

PARTUUID=6b8fd307-ae27-4222-b81c-926eaa800dbc /data ext4 defaults,nofail 0 2

Options

For all list of all options, see: Ext file system options and File system independent Options. Note that changing owner or permissions is only really needed for file system that don't support UNIX permissions, e.g NTFS. ext4 and others will save all permissions.

Name	Description
defaults	Commen Default settings. These include: rw,suid,dev,exec,auto,nouser,async,realtime
ro	Mount the file system in readonly mode
rw	Mount the file system in Read-Write mode (In defaults)
nofail	Skip the file system if it can't be found. Very usefull for thumb-drives. If this options is not set, the system will wait for the filesystem to be connected before booting
umask=PERMS	Set the Permissions for all files and directories. Important: This is a umask so its disallows permissions e.g. 000 becomes 777, 022becomes755.
uid=UID	Set the owner of all files. Can be the users UID or username.
gid=GID	Set the owner group of all files. Can be the groups GID or groupname.
windows_names	Only for NTFS: Prevent the creating of files with characters that are not allowed within Windows e.g. " * < > / | \ and some

Determine file system types and UUID

To list all partitions with their UUID execute:

sudo blkid -s UUID

Validating fstab

Executing mount -fav will try to mount all file systems without actually making a system call.

• -a Try to auto mount everything inside fstab.
• -f Fake, don't make any system calls.
• -v Verbose print more debug output.

Alternative findmnt --verify --verbose can print nice information and detailed error messages.

Output without any errors:

# findmnt --verify --verbose
/proc
   [ ] target exists
   [ ] do not check proc source (pseudo/net)
   [ ] do not check proc FS type (pseudo/net)
/boot
   [ ] target exists
   [ ] FS options: flush
   [ ] PARTUUID=0a70b801-01 translated to /dev/mmcblk0p1
   [ ] source /dev/mmcblk0p1 exists
   [ ] FS type is vfat
/
   [ ] target exists
   [ ] VFS options: noatime
   [ ] PARTUUID=0a70b801-02 translated to /dev/mmcblk0p2
   [ ] source /dev/mmcblk0p2 exists
   [ ] FS type is ext4
/data
   [ ] target exists
   [ ] userspace options: nofail
   [ ] PARTUUID=6b8fd307-ae27-4222-b81c-926eaa800dbc translated to /dev/sda1
   [ ] source /dev/sda1 exists
   [ ] FS type is ext4
Success, no errors or warnings detected

Output with wrong PARTUUID value:

# findmnt --verify --verbose
/proc
   [ ] target exists
...
   [ ] source /dev/mmcblk0p2 exists
   [ ] FS type is ext4
/data
   [ ] target exists
   [ ] userspace options: nofail
   [E] unreachable on boot required source: PARTUUID=6b8fd307-ae27-4222-b81c-926eaa800db

0 parse errors, 1 error, 0 warnings