mount filesystems in Linux/Unix

mount command is used for mounting (making available) filesystems in Linux and Unix.

Since a standard Unix-like filesystem layout consists of directories forming a tree, mounting a filesystem means attaching the logical storage of a given filesystem to one of the (usually empty) directories in the root filesystem.

For instance, /var and /opt and /home are usually created as separate filesystems. So they are automatically mounted as part of your Linux system boot. That’s why, when you cd into one of these directories, you see the contents of relevant filesystem.

mount command without options

If you don’t supply any command line parameters, mount will report the list of all the filesystems mounted at the moment.

Here’s how this looks in Ubuntu 16.04:

root@vps1:~# mount

sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)

proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)

udev on /dev type devtmpfs (rw,nosuid,relatime,size=487748k,nr_inodes=121937,mode=755)

devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)

tmpfs on /run type tmpfs (rw,nosuid,noexec,relatime,size=101276k,mode=755)

/dev/vda1 on / type ext4 (rw,relatime,data=ordered)

securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)

tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)

tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)

tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)

cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd)

pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)

efivarfs on /sys/firmware/efi/efivars type efivarfs (rw,nosuid,nodev,noexec,relatime)

cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)

cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)

cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)

cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)

cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)

cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)

cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)

cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)

cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)

cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)

systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=25,pgrp=1,timeout=0,minproto=5,maxproto=5,direct)

hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime)

debugfs on /sys/kernel/debug type debugfs (rw,relatime)

mqueue on /dev/mqueue type mqueue (rw,relatime)

fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)

/dev/vda15 on /boot/efi type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)

root@vps1:~#