Operating on disk devices¶
Listing devices.¶
Using lsblk.¶
You can get the block devices on your system by using lsblk:
$ lsblk -o NAME,TYPE,FSTYPE,LABEL,SIZE,MODEL,MOUNTPOINT
Which gives a schema like this:
sda disk 465.8G ST9500325AS
├─sda1 part 10M
└─sda2 part 419.2G
├─vg0-debian (dm-0) lvm 13.7G /
├─vg0-home (dm-1) lvm 23.4G /share/home
├─vg0-vguests (dm-2) lvm 56G
└─vg0-seafile (dm-3) lvm 2G
sdd disk 3.7G STORAGE DEVICE
└─sdd1 part vfat 3.7G
sr0 rom 1024M DVD+-RW GSA-T11N
You can also use the simpler lsblk -f with less columns.
Using blkid.¶
A detailled information with UUID, but not graphical is given by blkid, it should be run as root to give a full information.
$ sudo blkid -c /dev/null
The -c /dev/null is to prevent blkid from using cache, and
reporting devices which are no more available.
A more readable output is with:
$ sudo blkid -o list -c /dev/null /dev/sd*
device fs_type label mount point UUID
------------------------------------------------------
/dev/sda2 LVM2_member (in use) Fdh5Am-cNBo...
/dev/sdb1 vfat (not mounted) B49E-A10C
Or any device with:
$ sudo blkid -o list -c /dev/null
$ sudo blkid -o list -c /dev/null /dev/sdd1
$ sudo blkid -o list -c /dev/null /dev/mapper/*
Using udisk disk manager.¶
udisksctl is a higher level control part of the udisk disk manager If it is running on your system, you get the managed devices with their model, revision and serial number by:
$ udisksctl status
but it will not give you a partition list like lsblk or blkid which I find more informative for discovering new devices.
There are many way to know what partitions compose your storage devices like proc filesystem, the dev filesystem, or the commands: fdisk, sfdisk, gdisk, sgdisk or parted.
You may have to use a second level when the partition is not a physical partition but a logical partition. lvm volumes are grouped in volume groups divided in logical volumes that you can list using lvdisplay.
If the partition host a btrfs file system, you can list the subvolumes that compose it by using btrfs-subvolume.
When you add the device entry to udiskctl you obtain a more detailed info:
$ udisksctl info -b /dev/sdd
$ udisksctl info -b '/dev/sdd1'
$ udisksctl info -p 'block_devices/sdd'
$ udisksctl info -p 'block_devices/sdd1'
-p is an abbrev for --object-path and b an abbrev
for --block-device. In any case the block-device the
object-path is told in the answer.
You can also use udisksctl monitor to monitor devices
before connecting the device and see the
device entry attributed by udev.
It is also shown in your kernel messages, and can be read with dmesg but it is quite laborious to find the proper line.
Using the udev level for usb devices.¶
For an usb device you can also use lsusb:
$ lsusb -v | grep -E \
'\<(Bus|iProduct|bDeviceClass|bDeviceProtocol)' 2>/dev/null
You can also get the udev keys with udevadm, you have more details in the udev section.
$ udevadm info -a -n /dev/usb/sdb1
lsusb is aimed at usb devices, it can often be replaced by the more general commands lsblk and blkid.
Interacting with proc and sys.¶
If these command are not available you can work at low level with the proc and sys virtual filesystem.
$ cat /proc/partitions
major minor #blocks name
8 0 976762584 sda
8 1 409600 sda1
8 2 307200 sda2
....
$ ls -l /sys/block/*/device
lrwxrwxrwx 1 root root 0 Jan 25 21:10 /sys/block/sda/device -> ../../../0:0:0:0
lrwxrwxrwx 1 root root 0 Jan 25 21:12 /sys/block/sr0/device -> ../../../1:0:0:0
$ cat /sys/block/sr0/device/model
DVDRAM GUA0N
Using the dev filesystem.¶
udev populate the dev filesystem, you can explore it with
file --special-files abridged in file -s, as the
/dev entry also used symlinks to find device by label, id,
or uuid, you may need to use also the option --dereference (-L).
file -s give dor a device the type of boot sector, for a partition the file system type or LVM physical volumes and the UUID.
$ sudo file -s /dev/dm-*
$ sudo file -s /dev/sd*
$ sudo file -L -s /dev/disk/by-uuid/*
$ sudo file -L -s /dev/disk/by-label/*
Determine the file system of an unmounted partition.¶
When the partition is mounted the output of mount show the file system type.
You can also use df with the command:
$ df --print-type --human-readable
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg0-root ext3 19G 12G 6.2G 65% /
/dev/sda2 vfat 296M 50M 247M 17%
/boot/efi
....
Using short options the command is df -Th.
When the partition is not mounted whe have seen above that blkid also give the partition type, and it can even be run as a user, in this case he cannot tell if the partition is in use or not, but it still gives the fs type.
When you want to know the size and alignement of a partition you can use fdisk or sfdisk with mbr partition table gdisk or sgdisk with gpt partition table, and parted with both of them to issue one of:
$ sudo fdisk -l /dev/sdd
$ sudo sfdisk -l /dev/sdd
$ sudo gdisk -l /dev/sdd
$ sudo sgdisk -i -p /dev/sdd
$ sudo parted /dev/sdd print
All these command are to be run as root.
Mounting devices as user.¶
To mount the device as root you can of course use the mount
command, for removable devices, usually you prefer to mount them as
user.
You can still use mount if the fstab has a user option for
the device, but not for arbitrary plugged devices.
The old way is to use pmount, but if you have udisdk daemon running on your system, you should use udisksctl:
$ udisksctl mount -b /dev/sdd1
$ udisksctl mount -b /dev/disk/by-label/key64G001
$ udisksctl mount -b /dev/disk/by-uuid/77e19bbf-84ac-4336-a738-e6563a538f7d
$ udisksctl unmount -b /dev/sdd1
$ udisksctl power-off -b /dev/sdd1
The udisks daemon mount your block device in a directory
/media/<user> that it creates if necessary. If there is a label it is
used; so the device above key64G001 is mounted as
/media/<user>/key64G001.
The directory /media/<user> belongs to root, but has an ACL giving
you the r-x access. The directory /media/<user>/key64G001 and
its content belongs to to you with rwx access.
The mount directory is shown in the output of udisksctl, but if you don’t remember it, or you want to use it in a script, you can get it with the command findmnt:
findmnt -no TARGET /dev/disk/by-uuid/77e19bbf-84ac-4336-a738-e6563a538f7d
You can also use udisksctl to mount a loop device:
$ udisksctl loop-setup -f someimage.iso
Mapped file someimage.iso as /dev/loop0.
$ udisksctl mount -b /dev/loop0
Mounted /dev/loop0 at /media/john/someimage.
Mounting a partition in a FileManager¶
The modern file managers like Nautilus, Thunar, Pcmanfm use gvfs and udisk2 to mount removable media. They accept that you give them a gvfs mountpoint.
They also list a list of partition, either yet mounted, or unmouted, and allow to mount removable partitions.
Partitions listed in /etc/fstab would (by default) only show up if
they are mounted under /media, $HOME or /run/media/$USER
or if there is an entry in fstab for them pointing to these
directories.
If you want the partition to be mounted under a different directory
(e.g. /mnt) and still be shown in the sidebar, you can override the
default behaviour by adding x-gvfs-show to your mount options in
fstab:
Partitions not listed in /etc/fstab are handled by udisks2 and will be
mounted under /run/media/$USER/VolumeName or /media/VolumeName
depending on the value of UDISKS_FILESYSTEM_SHARED (see
udisks you can change it in an udev rule),
hence they will be shown under Devices in the sidebar.
Front ends for mounting removable devices.¶
You may also want to have some frontend that allows to alleviate the burden of remembering the commands or to read the manual, but which add the the load of remembering the frontend api, and make you depend on the presence of an added piece of software.
- bashmount is a bash script to help mounting with udisks2. It is not updted since 2014 but there are more recent forks.
- lightweight device mounter
(ldm) (MIT License)
is a lightweight daemon that mounts removable devices
automatically. Ut requires only libudev, libmount and libusb. The
daemon uses 3.3M resident with 2.5M shared. There are few
configuration options as it relies on fstab for mounting
partitions. There is no easy way to configure what you want to be
mounted by the daemon and my regular partitions yet mounted on a
system path get mounted again under
/mnt. - triggerhappy (GPL) is a hotkey daemon developed for small and embedded systems. It attaches to the input device files and executes scripts on events. It is packaged in Debian.
- udisk-glue (BSD Licence) is a daemon that can perform user-configurable actions when a certain udisks event is detected. It can be configured to automatically mount devices. Last commit 2013.
- udiskie
(MIT License) is an automounter for usb devices written in
python. It uses the dbus interface through udisks.
It comes with optional mount notifications and gtk
tray icon and a command-line client
udiskie-mount. It is in pypi. - UDisksEvt (GPL) by Vladimir Matveev is a daemon written ih haskell which listens for D-Bus signals emitted by UDisks daemon and execute configured actions. Last commit 2011
- udevil is a command line program which mounts and unmounts removable devices. Udevil is written in C with libudev and glib without dependency on udisks or gvfs. It is part of the Spacefm project whose development stopped in April 2014.
- usbmount
automatically mounts USB mass storage devices when they are
plugged in, and unmounts them when they are removed. The
mountpoints (
/media/usb[0-7]by default), filesystem types to consider, and mount options are configurable. If the device provides a model name, a symlink/var/run/usbmount/MODELNAMEpointing to the mountpoint is automatically created. usbmount is unmaintained since 2007 as a debian package and the last release is in Jessie, a git repository contains some new developpements. - udisksvm is a small (280 loc) python GUI oriented script to automount removable medias using udisks.
- udisks_functions are bash functions to help mounting and unmounting with udisks2.
All modern file managers can automount devices for lxde desktops see PCManFM
Udisks references¶
- ArchWiki: :archwiki:`Udisks.
- Gentoo: Udisks.
- Introduction to Udisks.
Loop Devices.¶
Mounting disk images¶
As an example I want to mount a partition in a disk image disk.img.
The output of file is:
$ file disk.img
disk.img: DOS/MBR boot sector; partition 1 : ID=0x83, start-CHS (0x40,0,1),
end-CHS (0x3ff,3,32), startsector 8192, 2048000 sectors
or with fdisk:
$ fdisk -l disk.img
Disk disk.img: 1004 MiB, 1052770304 bytes, 2056192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x081bc7ef
Device Boot Start End Sectors Size Id Type
disk.img1 8192 2056191 2048000 1000M 83 Linux
So first partition begin at 8192 x 512 = 4194304 bytes
I can mount it with
$ sudo mount -o ro,loop,offset=4194304 disk.img /tmp/mnt
We can check the mount with findmnt(8)
$ findmnt /tmp/mnt
TARGET SOURCE FSTYPE OPTIONS
/tmp/mnt /dev/loop0 ext4 ro,relatime
If you want to avoid the offset computing you can use kpartx(8), which set up device mappings for the partitions of any partitioned block device.
You can also create loop devices for each partition in your disk with:
$ sudo losetup -f -P disk.img
$ sudo mount -o ro,loop /dev/loop0p1
We can also use udisksctl to mount the disk partition as user.
$ udisksctl loop-setup --file disk.img --offset 4194304
Mapped file disk.img as /dev/loop0
$ udisksctl mount -b /dev/loop0
Mounted /dev/loop0 at /media/john/5853137f-ce83-4fa5-9845-42ff0de259b4
For unmountting:
$ udisksctl unmount -b /dev/loop0
$ udisksctl loop-delete -b /dev/loop0
With udisksctl you can also mount the whole disk, in contrast to losetup no extra option is needed.
$ udisksctl loop-setup --file disk.img
udisksctl mount -b /dev/loop0p1