How to use findmnt on CentOS 7

To use findmnt on CentOS 7  

findmnt is a linux command that will list all mounted filesystems or search for a filesystem. The findmnt command will search in the following directories, /etc/fstab, /etc/fstab.d, /etc/mtab or proc/self/mountinfo. If the given search filesystem is not found, all the existing filesystems are shown to the user. This tutorial explains the usage of findmnt on CentOS 7. 

Usage of findmnt command

List filesystems

To list the filesystems in the target machine, run the following findmnt command  without any options, it would simply list out all the mounted filesystems in a tree style layout.

[root@linuxhelp ~]# findmnt
TARGET                                SOURCE     FSTYPE          OPTIONS
/                                     /dev/sda3  ext4            rw,relatime,data=ordered
??/sys                                sysfs      sysfs           rw,nosuid,nodev,noexec,relatime
? ??/sys/kernel/security              securityfs securityfs      rw,nosuid,nodev,noexec,relatime
? ??/sys/fs/cgroup                    tmpfs      tmpfs           rw,nosuid,nodev,noexec,mode=755
? ? ??/sys/fs/cgroup/systemd          cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd
? ? ??/sys/fs/cgroup/cpuset           cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,cpuset
? ? ??/sys/fs/cgroup/cpu,cpuacct      cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,cpu,cpuacct
? ? ??/sys/fs/cgroup/blkio            cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,blkio
? ? ??/sys/fs/cgroup/memory           cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,memory
? ? ??/sys/fs/cgroup/devices          cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,devices
? ? ??/sys/fs/cgroup/freezer          cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,freezer
? ? ??/sys/fs/cgroup/net_cls,net_prio cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,net_cls,net_prio
? ? ??/sys/fs/cgroup/perf_event       cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,perf_event
? ? ??/sys/fs/cgroup/hugetlb          cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,hugetlb
? ??/sys/fs/pstore                    pstore     pstore          rw,nosuid,nodev,noexec,relatime
? ??/sys/kernel/debug                 debugfs    debugfs         rw,relatime
? ? ??/sys/kernel/debug/tracing       tracefs    tracefs         rw,relatime
? ??/sys/fs/fuse/connections          fusectl    fusectl         rw,relatime
??/proc                               proc       proc            rw,nosuid,nodev,noexec,relatime
? ??/proc/sys/fs/binfmt_misc          systemd-1  autofs          rw,relatime,fd=27,pgrp=1,timeout=300,minproto=5,maxproto=5,direct
??/dev                                devtmpfs   devtmpfs        rw,nosuid,size=768104k,nr_inodes=192026,mode=755
? ??/dev/shm                          tmpfs      tmpfs           rw,nosuid,nodev
? ??/dev/pts                          devpts     devpts          rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000
? ??/dev/mqueue                       mqueue     mqueue          rw,relatime
? ??/dev/hugepages                    hugetlbfs  hugetlbfs       rw,relatime
??/run                                tmpfs      tmpfs           rw,nosuid,nodev,mode=755
? ??/run/user/1000/gvfs               gvfsd-fuse fuse.gvfsd-fuse rw,nosuid,nodev,relatime,user_id=1000,group_id=100
??/boot                               /dev/sda2  ext4            rw,relatime,data=ordered

List style output  format 

Next, to view the output  in list format, execute the following command. The  filesystem is listed in the following order. 

[root@linuxhelp ~]# findmnt -l
TARGET                          SOURCE     FSTYPE          OPTIONS
/sys                            sysfs      sysfs           rw,nosuid,nodev,noexec,relatime
/proc                           proc       proc            rw,nosuid,nodev,noexec,relatime
/dev                            devtmpfs   devtmpfs        rw,nosuid,size=768104k,nr_inodes=192026,mode=755
/sys/kernel/security            securityfs securityfs      rw,nosuid,nodev,noexec,relatime
/dev/shm                        tmpfs      tmpfs           rw,nosuid,nodev
/dev/pts                        devpts     devpts          rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000
/run                            tmpfs      tmpfs           rw,nosuid,nodev,mode=755
/sys/fs/cgroup                  tmpfs      tmpfs           rw,nosuid,nodev,noexec,mode=755
/sys/fs/cgroup/systemd          cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd
/sys/fs/pstore                  pstore     pstore          rw,nosuid,nodev,noexec,relatime
/sys/fs/cgroup/cpuset           cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,cpuset
/sys/fs/cgroup/cpu,cpuacct      cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,cpu,cpuacct
/sys/fs/cgroup/blkio            cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,blkio
/sys/fs/cgroup/memory           cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,memory
/sys/fs/cgroup/devices          cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,devices
/sys/fs/cgroup/freezer          cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,freezer
/sys/fs/cgroup/net_cls,net_prio cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,net_cls,net_prio
/sys/fs/cgroup/perf_event       cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,perf_event
/sys/fs/cgroup/hugetlb          cgroup     cgroup          rw,nosuid,nodev,noexec,relatime,hugetlb
/                               /dev/sda3  ext4            rw,relatime,data=ordered
/proc/sys/fs/binfmt_misc        systemd-1  autofs          rw,relatime,fd=27,pgrp=1,timeout=300,minproto=5,maxproto=5,direct
/dev/mqueue                     mqueue     mqueue          rw,relatime
/dev/hugepages                  hugetlbfs  hugetlbfs       rw,relatime
/sys/kernel/debug               debugfs    debugfs         rw,relatime
/boot                           /dev/sda2  ext4            rw,relatime,data=ordered
/sys/fs/fuse/connections        fusectl    fusectl         rw,relatime
/run/user/1000/gvfs             gvfsd-fuse fuse.gvfsd-fuse rw,nosuid,nodev,relatime,user_id=1000,group_id=100
/sys/kernel/debug/tracing       tracefs    tracefs         rw,relatime

df style output format

The findmnt can produce a df style output that reports  free and used disk space with the " -D" or " --df" option.

[root@linuxhelp ~]# findmnt -D
SOURCE     FSTYPE            SIZE  USED  AVAIL USE% TARGET
devtmpfs   devtmpfs        750.1M     0 750.1M   0% /dev
tmpfs      tmpfs           755.6M  172K 755.4M   0% /dev/shm
tmpfs      tmpfs           755.6M  2.1M 753.5M   0% /run
tmpfs      tmpfs           755.6M     0 755.6M   0% /sys/fs/cgroup
/dev/sda3  ext4             17.1G  5.3G  10.9G  31% /
/dev/sda2  ext4            478.2M 53.4M 395.7M  11% /boot
gvfsd-fuse fuse.gvfsd-fuse      0     0      0    - /run/user/1000/gvfs
tracefs    tracefs              0     0      0    - /sys/kernel/debug/tracing

Read filesystems from fstab

With the ' -s' or ' --fstab' option, findmnt will read filesystems only from the /etc/fstab file and /etc/fstab.d directory.

[root@linuxhelp ~]# findmnt -s
TARGET SOURCE                                    FSTYPE OPTIONS
swap   UUID=cda4ad98-7d97-40e1-8269-48978acfd4ee swap   defaults
/      UUID=d615b88e-7e76-4cc1-b0a2-08d405d39af7 ext4   acl,user_xattr
/boot  UUID=8f597409-b13d-4998-8f79-919a7f6372ae ext4   acl,user_xatt

Filter filesystems by type

The findmnt command  can be viewed  by mentioning the specific filesystems based on the type of file.  Multiple system types can be specified separated by a comma. Execute the following command to view the filesystems by type. 

[root@linuxhelp ~]# findmnt -t ext4
TARGET  SOURCE    FSTYPE OPTIONS
/       /dev/sda3 ext4   rw,relatime,data=ordered
??/boot /dev/sda2 ext4   rw,relatime,data=ordered

Raw output

To view the output in raw style,  run the following command and use the  ' -r' or ' --raw' option.

[root@linuxhelp ~]# findmnt --raw
TARGET SOURCE FSTYPE OPTIONS
/sys sysfs sysfs rw,nosuid,nodev,noexec,relatime
/proc proc proc rw,nosuid,nodev,noexec,relatime
/dev devtmpfs devtmpfs rw,nosuid,size=768104k,nr_inodes=192026,mode=755
/sys/kernel/security securityfs securityfs rw,nosuid,nodev,noexec,relatime
/dev/shm tmpfs tmpfs rw,nosuid,nodev
/dev/pts devpts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000
/run tmpfs tmpfs rw,nosuid,nodev,mode=755
/sys/fs/cgroup tmpfs tmpfs rw,nosuid,nodev,noexec,mode=755
/sys/fs/cgroup/systemd cgroup cgroup rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd
/sys/fs/pstore pstore pstore rw,nosuid,nodev,noexec,relatime
/sys/fs/cgroup/cpuset cgroup cgroup rw,nosuid,nodev,noexec,relatime,cpuset
/sys/fs/cgroup/cpu,cpuacct cgroup cgroup rw,nosuid,nodev,noexec,relatime,cpu,cpuacct
/sys/fs/cgroup/blkio cgroup cgroup rw,nosuid,nodev,noexec,relatime,blkio
/sys/fs/cgroup/memory cgroup cgroup rw,nosuid,nodev,noexec,relatime,memory
/sys/fs/cgroup/devices cgroup cgroup rw,nosuid,nodev,noexec,relatime,devices
/sys/fs/cgroup/freezer cgroup cgroup rw,nosuid,nodev,noexec,relatime,freezer
/sys/fs/cgroup/net_cls,net_prio cgroup cgroup rw,nosuid,nodev,noexec,relatime,net_cls,net_prio
/sys/fs/cgroup/perf_event cgroup cgroup rw,nosuid,nodev,noexec,relatime,perf_event
/sys/fs/cgroup/hugetlb cgroup cgroup rw,nosuid,nodev,noexec,relatime,hugetlb
/ /dev/sda3 ext4 rw,relatime,data=ordered
/proc/sys/fs/binfmt_misc systemd-1 autofs rw,relatime,fd=27,pgrp=1,timeout=300,minproto=5,maxproto=5,direct
/dev/mqueue mqueue mqueue rw,relatime
/dev/hugepages hugetlbfs hugetlbfs rw,relatime
/sys/kernel/debug debugfs debugfs rw,relatime
/boot /dev/sda2 ext4 rw,relatime,data=ordered
/sys/fs/fuse/connections fusectl fusectl rw,relatime
/run/user/1000/gvfs gvfsd-fuse fuse.gvfsd-fuse rw,nosuid,nodev,relatime,user_id=1000,group_id=100
/sys/kernel/debug/tracing tracefs tracefs rw,relatime

Search by source device

To find the filesystem by the source device, specify the device path with or without the ' -S' option. 

[root@linuxhelp ~]# findmnt -S /dev/sda2
TARGET SOURCE    FSTYPE OPTIONS
/boot  /dev/sda2 ext4   rw,relatime,data=ordered

Search by mount point

To search filesystem by the mount directory , specify the directory with or without the ' -T' /' --target' option.

[root@linuxhelp ~]# findmnt -T /dev/
/dev/hugepages  /dev/mqueue     /dev/pts        /dev/shm        

[root@linuxhelp ~]# findmnt -T /dev/
/dev/hugepages  /dev/mqueue     /dev/pts        /dev/shm     
   
[root@linuxhelp ~]# findmnt -T /dev/shm
TARGET   SOURCE FSTYPE OPTIONS
/dev/shm tmpfs  tmpfs  rw,nosuid,nodev

Thus we conclude the usage of findmnt command on CentOS 7.