LINUX FSTAB – MOUNT TABLE

Linux’s Mount Table /etc/fstab

root@centos ~]# cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Wed Jan  9 22:27:17 2013
#
/dev/mapper/vg_centos-lv_root /                       ext4    defaults  1 1
UUID=65e88b9b-a4b7-408b-86a5-335c9f91c404 /boot       ext4    defaults  1 2
/dev/mapper/vg_centos-lv_swap swap                    swap    defaults  0 0
tmpfs                   /dev/shm                tmpfs   defaults  0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults  0 0
proc                    /proc                   proc    defaults  0 0
#
# Added for fstab demo landoflinux.com
#
/dev/sdb1               /test1                  ext3    defaults  0 0
/dev/sdb2               /test2                  ext3    defaults  0 0
/dev/sdb3               /test3                  ext3    defaults  0 0
/dev/sdb5               /test4                  ext3    defaults  0 0
/dev/sdb6               /test5                  ext3    defaults  0 0
/dev/sdb7               /test6                  ext3    defaults  0 0
/dev/sdb8               /test7                  ext3    defaults  0 0

The location of the mount table is held in a file located in the following path: « /etc/fstab ». This file is generally maintained by the system administrator of the server. Each line within the file describes the device/filesystems that are available to your system. Each field is separated by spaces or a tab. There are six fields for each entry:

Field One: Filesystem – This field describes the device or filesystem that is to be mounted. Ordinary mounts such as « /dev/sdb1 » can be seen here. You may also come across NFS mounts. These are filesystems that are hosted by a remote server. These can be identified easily by the « nfs »

/rmtserver:/opt/test /mynfs nfs ro,bg 0 0

The above « nfs » example will mount « /opt/test » from the remote server « rmtserver » on the local mount point « /mynfs ». This will be a read only mount. The « bg » specifies that it should be mounted as a background task.

On many newer systems it is quite common to see devices specified by there « UUID » Universal Unique Identifier.

Field Two: Mount Point field. For a « swap » partition this field should be specified as « none ».

Field Three: This field describes the type of filesystem. Linux can support many different filesystems – « ext2, ext3, ext4, hfs, iso9600, minix, msdos, nfs, ntfs, reiserfs, smbfs, vfat, xfs plus many more. » For filesystems supported by the running kernel see « /proc/filesystems ».

Field Four: This field describes the mount options associated with the filesystem. This is a comma separated list. It should contain the type of mount plus any additional options.

Basic Filesystem options:

defaults
Use default options: rw, suid, dev, exec, auto, nouser and async.

auto
Mount automatically at boot time.

noauto
Do not mount automatically at boot time.

user
Allow a normal user to mount.

owner
Allow device owner to mount.

comment
Used by fstab maintaining programs.

nofail
Do not report errors if this does not exist.

Field Five:This field is used to identify which filesystems should by dumped by the « dump » command. A value of zero « 0 » indicates that no dump is to take place.

Field Six:This field is used by the « fsck » program to determine the order of which filesystems checks are done at reboot time. The « / » root filesystem should have a value of « 1 » and other filesystems should have a value of « 2 ». If this filed is not present or has a value of « 0 » then it is assumed that no check is to take place.