Difference between ‘mount’ and ‘mount -a’
There is a slight difference between the commands - “mount” and “mount -a”.
1. When you type “mount”, it will display the output of the file “/etc/mtab”.
For example,
/dev/sda5 on / type ext3 (rw,usrquota)
none on /proc type proc (rw)
none on /sys type sysfs (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
usbfs on /proc/bus/usb type usbfs (rw)
/dev/sda1 on /boot type ext3 (rw)
none on /dev/shm type tmpfs (rw)
/dev/sda7 on /home type ext3 (rw,usrquota)
/dev/sda8 on /tmp type ext3 (rw,noexec,nosuid)
/dev/sda3 on /usr type ext3 (rw,usrquota)
/dev/sda2 on /var type ext3 (rw,usrquota)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
/tmp on /var/tmp type none (rw,noexec,nosuid,bind)
The content of the file “/etc/mtab” is:
/dev/sda5 / ext3 rw,usrquota 0 0
none /proc proc rw 0 0
none /sys sysfs rw 0 0
none /dev/pts devpts rw,gid=5,mode=620 0 0
usbfs /proc/bus/usb usbfs rw 0 0
/dev/sda1 /boot ext3 rw 0 0
none /dev/shm tmpfs rw 0 0
/dev/sda7 /home ext3 rw,usrquota 0 0
/dev/sda8 /tmp ext3 rw,noexec,nosuid 0 0
/dev/sda3 /usr ext3 rw,usrquota 0 0
/dev/sda2 /var ext3 rw,usrquota 0 0
none /proc/sys/fs/binfmt_misc binfmt_misc rw 0 0
sunrpc /var/lib/nfs/rpc_pipefs rpc_pipefs rw 0 0
/tmp /var/tmp none rw,noexec,nosuid,bind 0 0
2. When you type the command “mount -a”, it will take the output of the file “/etc/fstab”.
# This file is edited by fstab-sync - see ‘man fstab-sync’ for details
LABEL=/                 /                       ext3    defaults,usrquota        1 1
LABEL=/boot             /boot                   ext3    defaults        1 2
none                    /dev/pts                devpts  gid=5,mode=620  0 0
none                    /dev/shm                tmpfs   defaults        0 0
LABEL=/home             /home                   ext3    defaults,usrquota        1 2
none                    /proc                   proc    defaults        0 0
none                    /sys                    sysfs   defaults        0 0
LABEL=/tmp              /tmp                    ext3    defaults        1 2
LABEL=/usr              /usr                    ext3    defaults,usrquota        1 2
LABEL=/var              /var                    ext3    defaults,usrquota        1 2
LABEL=SWAP-sda6         swap                    swap    pri=0,defaults        0 0
Note: The file “/etc/mtab” has the entries of temporary partitions such as USB drive. But, the file “/etc/fstab” has the entries of mounted partitions in the server.
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