Is there a simple command that takes a disk's device node as input, and tells me where (and whether) that disk is mounted? Is it possible to get the mount point by itself, so I can pass it to another command?
I'm working on a Debian Squeeze live system with a minimal install (I can install extra packages if need be).
On Linux, you can now use the findmnt command from util-linux (since version 2.18):
$ findmnt -S /dev/VG_SC/home
TARGET SOURCE FSTYPE OPTIONS
/home /dev/mapper/VG_SC-home ext4 rw,relatime,errors=remount-ro,data=ordered
Or lsblk (also from util-linux, since 2.19):
$ lsblk /dev/VG_SC/home
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
VG_SC-home 254:2 0 200G 0 lvm /home
That one is also useful to find all the file system mounted under a specific device (disk or partition...):
$ lsblk /dev/sda2
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda2 8:2 0 59.5G 0 part
├─linux-debian64 (dm-1) 252:1 0 15G 0 lvm
└─linux-mint (dm-2) 252:2 0 15G 0 lvm /
To get the mountpoint only:
$ findmnt -nr -o target -S /dev/storage/home
/home
$ lsblk -o MOUNTPOINT -nr /dev/storage/home
/home
Above findmnt does return with a failure exit status if the device is not mounted, not lsblk.
So:
if mountpoint=$(findmnt -nr -o target -S "$device"); then
printf '"%s" is mounted on "%s"\n' "$device" "$mountpoint"
else
printf '"%s" does not appear to be directly mounted\n' "$device"
fi
Under Linux, you can get mount point information directly from the kernel in /proc/mounts. The mount program records similar information in /etc/mtab. The paths and options may be different, as /etc/mtab represents what mount passed to the kernel whereas /proc/mounts shows the data as seen inside the kernel. /proc/mounts is always up-to-date whereas /etc/mtab might not be if /etc was read-only at some point that wasn't expected by the boot scripts. The format is similar to /etc/fstab.
In both files, the first whitespace-separated field contains the device path and the second field contains the mount point.
awk -v needle="$device_path" '$1==needle {print $2}' /proc/mounts
or if you don't have awk:
grep "^$device_path " /proc/mounts | cut -d ' ' -f 2
There are a number of edge cases where you might not get what you expect. If the device was mounted via a different path in /dev that designates the same device, you won't notice it this way. In /proc/mounts, bind mounts are indistinguishable from the original. There may be more than one match if a mount point shadows another (this is unusual).
In /proc/self or /proc/$pid, there is a per-process mounts file that mimics the global file. The mount information may vary between processes, for example due to chroot. There is an additional file called mountinfo that has a different format and includes more information, in particular the device major and minor numbers. From the documentation:
36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
(1) mount ID: unique identifier of the mount (may be reused after umount)
(2) parent ID: ID of parent (or of self for the top of the mount tree)
(3) major:minor: value of st_dev for files on filesystem
(4) root: root of the mount within the filesystem
(5) mount point: mount point relative to the process's root
(6) mount options: per mount options
(7) optional fields: zero or more fields of the form "tag[:value]"
(8) separator: marks the end of the optional fields
(9) filesystem type: name of filesystem of the form "type[.subtype]"
(10) mount source: filesystem specific information or "none"
(11) super options: per super block options
So if you're looking for a device by number, you can do it like this:
awk -v dev="$major:minor" '$3==dev {print $5}'
awk -v dev="$(stat -L -c %t:%T /dev/block/something)" '$3==dev {print $5}'
The mount command with no arguments will list all currently mounted filesystems; you can grep that for the disk you want (or grep /etc/mtab, which is the file mount reads the information from):
$ grep /dev/sda /etc/mtab
/dev/sda3 /boot ext2 rw,noatime 0 0
Yes. You can see Showing Only Interesting Mount Points/Filtering Non-Interesting Types or Listing Directories under / that are Not Under the Same Mountpoint for some example usage, but there's also a brief rundown below. The command you are asking about is findmnt (though lsblk might also serve):
lsblk -f /dev/sda[12]
NAME FSTYPE LABEL UUID MOUNTPOINT
sda1 vfat ESP F0B7-5DAE /esp
sda2 btrfs sys 94749918-bde1-46e6-b77c-b66e0368ecdb /
Now, as you can see, /dev/sda1 is mounted on /esp. I wonder if it is mounted elsewhere as well?
findmnt /dev/sda1
TARGET SOURCE FSTYPE OPTIONS
/esp /dev/sda1 vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro
/boot /dev/sda1[/EFI/arch_root] vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro
Aha. I see. A subfolder is also --bind mounted over boot. Ok...
sudo umount /boot /esp
findmnt /dev/sda1
Nothing. What the hell?
echo "$?"
1
Ohhh... Well, that's nice. Hmmm...
for d in 1 2
do findmnt "/dev/sda$d" >/dev/null
printf "/dev/sda$d%.$((6>>!$?))s%s\n"\
" isn't" " currently mounted."
done
/dev/sda1 isn't currently mounted.
/dev/sda2 is currently mounted.
Oh, yeah, that's really nice.
for d in /dev/sd*
do findmnt -noSOURCE,TARGET "$d"
done
/dev/sda2[/arch_root] /
Now let's put sda1 back where it belongs and try that again...
sudo mount -a
for d in /dev/sd*
do findmnt -noSOURCE,TARGET "$d"
done
/dev/sda1 /esp
/dev/sda1[/EFI/arch_root] /boot
/dev/sda2[/arch_root] /
But where did I find this magical command?
man mount | sed -e:n -e'/findmnt/!d;N;/\n$/q;bn'For more robust and customizable output use
findmnt(8), especially in your scripts. Note that control characters in the mountpoint name are replaced with?.
I don't know of a clean and simple way to detect whether or not a device node in /dev is mounted. This is what I can offer, though. It handles directly mounted devices (/dev/sda1) and devices mounted by UUID (/dev/disk/by-uuid/aa4e7b08-6547-4b5a-85ad-094e9e1af74f). It breaks if your device names contain whitespace.
deviceIsMounted()
{
local DEVICE="$1"
local MOUNT=$(
(
echo "$DEVICE"
find /dev -type l -lname "*${DEVICE/*\/}" -exec readlink -f {} \; -print |
xargs -n2 |
awk -v device="$DEVICE" '$1 == device {print $2}'
) |
xargs -n1 -i{} grep -F {} /proc/mounts
)
test -n "$MOUNT" && echo "$MOUNT"
}
deviceIsMounted /dev/sda1 && echo yes # Mountpoint and status
deviceIsMounted /dev/md2 >/dev/null && echo yes # Just status
The function writes the entry from /proc/mounts to stdout if found, also setting exit status to 0. Otherwise the exit status is 1.
