fstab

Related articles
Persistent block device naming
File systems
tmpfs
swap
genfstab
The
fstab(5)
file can be used to define how disk partitions, various other block devices, or remote file systems should be mounted into the file system.
Each file system is described in a separate line. These definitions will be converted into
systemd
mount units dynamically at boot, and when the configuration of the system manager is reloaded. The default setup will automatically
fsck
and mount file systems before starting services that need them to be mounted. For example, systemd automatically makes sure that remote file system mounts like
NFS
or
Samba
are only started after the network has been set up. Therefore, local and remote file system mounts specified in
/etc/fstab
should work out-of-the-box. See
systemd.mount(5)
for details.
The
mount
command will use fstab, if just one of either directory or device is given, to fill in the value for the other parameter. When doing so, mount options which are listed in fstab will also be used.
This article or section needs expansion.
Reason:
Explain what
systemd-remount-fs.service(8)
does and suggest using
rootflags
for mount options that cannot be applied by remounting. (Discuss in
Talk:Fstab
)
Usage
A simple
/etc/fstab
, using file system UUIDs:
/etc/fstab
# <device>                                <dir> <type> <options>                                        <dump> <fsck>
UUID=0a3407de-014b-458b-b5c1-848e92a327a3 /     ext4 defaults                                           0      1
UUID=CBB6-24F2                            /boot vfat defaults,nodev,nosuid,noexec,fmask=0177,dmask=0077 0      2
UUID=f9fe0b69-a280-415d-a03a-a32752370dee none  swap defaults                                           0      0
UUID=b411dc99-f0a0-4c87-9e05-184977be8539 /home ext4 defaults                                           0      2
<device>
describes the block special device or remote file system to be mounted; see
#Identifying file systems
.
<dir>
is the directory where the file system will be
mounted
to, a.k.a. the mountpoint. The directory must be created beforehand.
<type>
is the
file system
type.
<options>
are the file system mount options; see
mount(8) § FILESYSTEM-INDEPENDENT MOUNT OPTIONS
and
ext4(5) § Mount options for ext4
.
<dump>
is checked by the
dump(8)
utility. This field is usually set to
0
, which disables the check.
<fsck>
sets the order for file system checks at boot time; see
fsck(8)
. For the root device it should be
1
. For other partitions it should be
2
, or
0
to disable checking.
Tip
The
auto
type lets the mount command guess what type of file system is used. This is useful for
optical media
(CD/DVD/Blu-ray).
If the root file system is
btrfs
or
XFS
, the fsck order should be set to
0
instead of
1
. See
fsck.btrfs(8)
and
fsck.xfs(8)
.
All specified devices within
/etc/fstab
will be automatically mounted on startup and when the
-a
flag is used with
mount(8)
unless the
noauto
option is specified. Devices that are listed and not present will result in an error unless the
nofail
option is used.
See
fstab(5) § DESCRIPTION
for details.
Identifying file systems
This article or section needs expansion.
Reason:
There are more device paths than just kernel name descriptors.
/dev/disk/by-*/*
,
/dev/mapper/*
,
/dev/md/*
have various levels of persistence and there should be no issue using them. (Discuss in
Talk:Fstab
)
There are different ways to identify file systems that will be mounted in
/etc/fstab
: kernel name descriptor, file system label and UUID, and GPT partition label and UUID for GPT disks. Kernel name descriptors should not be used, while UUIDs or PARTUUIDs should be preferred over labels. See
Persistent block device naming
for more explanations. It is recommended to read that article first before continuing with this article.
In this section, we will describe how to mount file systems using all the mount methods available via examples. The output of the commands
lsblk -f
and
blkid
used in the following examples are available in the article
Persistent block device naming
.
Kernel name descriptors
Run
lsblk -f
to list the partitions and prefix the values in the
NAME
column with
/dev/
.
/etc/fstab
# <device <dir> <type> <options>                                          <dump> <fsck>
/dev/sda2 /     ext4   defaults                                           0      1
/dev/sda1 /boot vfat   defaults,nodev,nosuid,noexec,fmask=0177,dmask=0077 0      2
/dev/sda3 /home ext4   defaults                                           0      2
/dev/sda4 none  swap   defaults                                           0      0
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
).
File system labels
Run
lsblk -f
to list the partitions, and prefix the values in the
LABEL
column with
LABEL=
or alternatively run
blkid
and use the LABEL values without the quotes:
/etc/fstab
# <device>   <dir> <type> <options>                                          <dump> <fsck>
LABEL=System /     ext4   defaults                                           0      1
LABEL=ESP    /boot vfat   defaults,nodev,nosuid,noexec,fmask=0177,dmask=0077 0      2
LABEL=Data   /home ext4   defaults                                           0      2
LABEL=Swap   none  swap   defaults                                           0      0
Note
If any of your fields contains spaces, see
#Filepath spaces
.
File system UUIDs
Run
lsblk -f
to list the partitions, and prefix the values in the
UUID
column with
UUID=
or alternatively run
blkid
and use the UUID values without the quotes:
/etc/fstab
# <device>                                <dir> <type> <options>                                        <dump> <fsck>
UUID=0a3407de-014b-458b-b5c1-848e92a327a3 /     ext4 defaults                                           0      1
UUID=CBB6-24F2                            /boot vfat defaults,nodev,nosuid,noexec,fmask=0177,dmask=0077 0      2
UUID=b411dc99-f0a0-4c87-9e05-184977be8539 /home ext4 defaults                                           0      2
UUID=f9fe0b69-a280-415d-a03a-a32752370dee none  swap defaults                                           0      0
GPT partition labels
Run
blkid
to list the partitions, and use the
PARTLABEL
values without the quotes:
/etc/fstab
# <device>                           <dir> <type> <options>                                        <dump> <fsck>
PARTLABEL=GNU/Linux                  /     ext4 defaults                                           0      1
PARTLABEL=EFI\040system\040partition /boot vfat defaults,nodev,nosuid,noexec,fmask=0177,dmask=0077 0      2
PARTLABEL=Home                       /home ext4 defaults                                           0      2
PARTLABEL=Swap                       none  swap defaults                                           0      0
Note
If any of your fields contains spaces, see
#Filepath spaces
.
GPT partition UUIDs
Run
blkid
to list the partitions, and use the
PARTUUID
values without the quotes:
/etc/fstab
# <device>                                    <dir> <type> <options>                                        <dump> <fsck>
PARTUUID=98a81274-10f7-40db-872a-03df048df366 /     ext4 defaults                                           0      1
PARTUUID=d0d0d110-0a71-4ed6-936a-304969ea36af /boot vfat defaults,nodev,nosuid,noexec,fmask=0177,dmask=0077 0      2
PARTUUID=7280201c-fc5d-40f2-a9b2-466611d3d49e /home ext4 defaults                                           0      2
PARTUUID=039b6c1c-7553-4455-9537-1befbc9fbc5b none  swap defaults                                           0      0
Tips and tricks
Automount with systemd
See
systemd.mount(5)
for all systemd mount options.
Local partition
In case of a large partition, it may be more efficient to allow services that do not depend on it to start while it is checked by
fsck
. This can be achieved by adding the following options to the
/etc/fstab
entry of the partition:
x-systemd.automount
This will fsck and mount the partition only when it is first accessed, and the kernel will buffer all file access to it until it is ready.
This method can be relevant if one has, for example, a significantly large
/home
partition.
Note
This will make the file system type
autofs
which is ignored by
locate
by default.
Remote file system
The same applies to remote file system mounts. If you want them to be mounted only upon access, you will need to use the
x-systemd.automount
parameters. In addition, you can use the
x-systemd.mount-timeout=
option to specify how long systemd should wait for the mount command to finish. Also, the
_netdev
option ensures systemd understands that the mount is network dependent and order it after the network is online.
x-systemd.automount,x-systemd.mount-timeout=30,_netdev
Encrypted file system
If you have secondary encrypted file systems with keyfiles, you can also add the
nofail
parameter to the corresponding entries in
/etc/crypttab
and
/etc/fstab
.
systemd
will not wait for the cryptsetup service to finish unlocking and mounting the filesystem on boot, but instead may finish mounting this after reaching default.target. This will avoid any boot delay caused by unlocking secondary partitions that are not required immediately after boot. See
dm-crypt/System configuration#Non blocking mounting
for cryptsetup configuration
Since mount services will by default only wait for 90 seconds for the partition to be available, any delay in making the keyfile available may cause the mount to fail. To avoid this, add the option
x-systemd.mount-timeout=0
to fstab in order to make sure that the mount service waits indefinitely for the partition to be unlocked.
/etc/fstab
UUID=0a3407de-014b-458b-b5c1-848e92a327a3 /data ext4 defaults,nofail,x-systemd.device-timeout=0    0 2
Automatic unmount
You may also specify an idle timeout for a mount with the
x-systemd.idle-timeout
flag.  For example:
x-systemd.automount,x-systemd.idle-timeout=1min
This will make systemd unmount the mount after it has been idle for 1 minute.
External devices
The factual accuracy of this article or section is disputed.
Reason:
the nofail option does not work as described here. (Discuss in
Talk:Fstab#3.2 External Device options
)
External devices that are to be mounted when present but ignored if absent may require the
nofail
option. This prevents errors being reported at boot. For example:
/etc/fstab
LABEL=MyExternalDrive /media/backup    jfs    nofail,x-systemd.device-timeout=5    0  2
The
nofail
option is best combined with the
x-systemd.device-timeout
option. This is because the default device timeout is 90 seconds, so a disconnected external device with only
nofail
will make your boot take 90 seconds longer, unless you reconfigure the timeout as shown. Make sure not to set the timeout to 0, as this translates to infinite timeout.
Filepath spaces
Since spaces are used in
fstab
to delimit fields, if any field (
PARTLABEL
,
LABEL
or the mount point) contains spaces, these spaces must be replaced by escape characters
\
followed by the 3 digit octal code
040
:
/etc/fstab
UUID=47FA-4071         /home/username/Camera
\040
Pictures   vfat  defaults      0  0
LABEL=Storage
\040
drive /media/100
\040
GB
\040
(Storage)       ext4  defaults,user 0  2
atime options
Below atime options can impact drive performance.
The
strictatime
option updates the access time of the files every time they are accessed. This is more purposeful when Linux is used for servers; it does not have much value for desktop use. The drawback about the
strictatime
option is that even reading a file from the page cache (reading from memory instead of the drive) will still result in a write.
The
noatime
option fully disables writing file access times to the drive every time you read a file. This works well for almost all applications, except for those that need to know if a file has been read since the last time it was modified. The write time information to a file will continue to be updated anytime the file is written to with this option enabled.
The
nodiratime
option disables the writing of file access times only for directories while other files still get access times written.
Note
noatime
implies
nodiratime
.
You do not need to specify both
.
relatime
updates the access time only if the previous access time was earlier than the current modify or change time. In addition, since Linux 2.6.30, the access time is always updated if the previous access time was more than 24 hours old. This option is used when the
defaults
option,
atime
option (which means to use the kernel default, which is
relatime
; see
mount(8)
and
Once upon atime
) or no options at all are specified.
When using
Mutt
or other applications that need to know if a file has been read since the last time it was modified, the
noatime
option should not be used; using the
relatime
option is acceptable and still provides a performance improvement.
Since kernel 4.0 there is another related option:
lazytime
reduces writes to disk by maintaining changes to inode timestamps (access, modification and creation times) only in memory. The on-disk timestamps are updated only when either (1) the file inode needs to be updated for some change unrelated to file timestamps, (2) a sync to disk occurs, (3) an undeleted inode is evicted from memory or (4) if more than 24 hours passed since the last time the in-memory copy was written to disk.
Warning
In the event of a system crash, the access and modification times on disk might be out of date by up to 24 hours.
Note that the
lazytime
option works
in combination
with the aforementioned
*atime
options, not as an alternative. That is
relatime
by default, but can be even
strictatime
with the same or less cost of disk writes as the plain
relatime
option.
Remounting the root partition
If for some reason the root partition has been improperly mounted read only, remount the root partition with read-write access with the following command:
# mount -o remount,rw /
GPT partition automounting
When using UEFI/GPT, it is possible to omit certain partitions from
/etc/fstab
by partitioning according to the
Discoverable Partitions Specification
and have
systemd-gpt-auto-generator(8)
mount the partitions. See
systemd#GPT partition automounting
.
To specify custom mount options for these volumes, use a
by-designator identifier
as the device name:
/etc/fstab
/dev/disk/by-designator/root  /     ext4  defaults,noatime  0 1
/dev/disk/by-designator/swap  none  swap  defaults,discard  0 0
Bind mount
You can link directories with the
bind
option:
/etc/fstab
# <device>                             <dir>                         <type> <options>     <dump> <fsck>
UUID=94649E22649E06E0                  /media/user/OS/               ntfs    defaults,rw,errors=remount-ro  0  0
/media/user/OS/Users/user/Music/       /home/user/Music/             none    defaults,bind 0   0
/media/user/OS/Users/user/Pictures/    /home/user/Pictures/          none    defaults,bind 0   0
/media/user/OS/Users/user/Videos/      /home/user/Videos/            none    defaults,bind 0   0
/media/user/OS/Users/user/Downloads/   /home/user/Downloads/         none    defaults,bind 0   0
/media/user/OS/Users/user/Documents/   /home/user/Documents/         none    defaults,bind 0   0
/media/user/OS/Users/user/projects/    /home/user/projects/windows/  none    defaults,bind 0   0
See
mount(8) § Bind mount operation
for details.
Automatically generate an fstab using genfstab
You can use the
genfstab
tool to create an fstab file. See
genfstab
for details.
GUI utilities
Here is a list of programs that can be used to modify mount points. They might not have all the features possible for editing fstab, but have all of the most used ones and might make your workflow much easier:
GNOME Disks
— A GNOME utility for dealing with storage devices. Part of
gnome
.
https://apps.gnome.org/DiskUtility/
||
gnome-disk-utility
KDE Partition Manager
— Utility to help you manage the disks, partitions, and file systems on your computer. Part of
kde-system
.
https://apps.kde.org/partitionmanager/
||
partitionmanager
Modifying user permissions and ownership
If you want to allow any user to mount the drive, consider adding these mount options to add onto your fstab entries.
Note
This is also used for filesystems that do not have file permission abilities, which will also set the owner and permissions of the entire drive to the user who mounted it.
users
- Allow any user to mount and to unmount the filesystem, even when some other ordinary user mounted it. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line users,exec,dev,suid). Simply add
users
to the mount options to enable this.
user
- Allow an ordinary user to mount the filesystem. Only allows the same user to unmount. This option implies the options noexec, nosuid, and nodev (unless overridden by subsequent options, as in the option line user,exec,dev,suid). Simply add
user
to the mount options to enable this.
For filesystems that do not have file permissions built in such as FAT and exFAT, you can explicitly set the user or group for the entire drive and its files. You can view the ID of a specific user in
/etc/passwd
. The uid is the third number in the entry, and the group id is the fourth.
uid
- Set the owner ID of the drive
gid
- Set the group ID of the drive
For ext4, btrfs, and other filesystems that have permission abilities, other users might not be permitted to see the drive. Be sure to double check the permissions of
/path/to/drive/
and modify them for what you need.
Verify changes
Use
findmnt --verify --verbose
to check for syntax errors and invalid options in fstab.
See also
Full device listing including block device
Filesystem Hierarchy Standard
30x Faster Cache and Site Speed with TMPFS