Devices and Mount

calendar Jan 7, 2024 · 2 min read · linux  ·
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About the linux directory tree

  • Linux has a single directory tree, starting with the root directory
  • Othe oerating systems use different methods to refer to the same information.
    Microsoft Windows for example, uses a single tree for each device. It uses letters to refer to thise devices.
    eg: a:\mydir\myfile.txt
    is a file called myfile.txt in a directory called mydir, inside a diskette inserted into drive a:
  • If you are a newcomer to UNIX systems (linux as an example), it can be a little confusing.

Linux Devices

  • The Linux filesystem does not show only files
  • cd into the /dev directiry and look at what you see there:
1cd /dev
2ls -l
  • Here's an example from what I see in my Debian-11 Linux.
    I just cut a few of the lines
1...
2brw-rw----  1 root    disk      8,   0 Sep 20 09:49 sda
3brw-rw----  1 root    disk      8,   1 Sep 20 09:49 sda1
4brw-rw----  1 root    disk      8,   2 Sep 20 09:49 sda2
5brw-rw----  1 root    disk      8,   3 Sep 20 09:49 sda3
6brw-rw----  1 root    disk      8,   4 Sep 20 09:49 sda4
7...
  • These entries are not files, nor are they directories.
    They are devices, in this case a hard disk drive (sda) and the partitions inside it (sda1, sda2, ...)
  • Note the letter b at the beginning of each line, specifying this as a block device.
    Disks, SSDs and the such are block devices.
  • Other files has a c, and that means that they are charcter devices
  • We use the mount command to attach a device to specific location inside the directory tree.

Showing mounts

  • Use the mount command to show mounts.
    (there may be several of them)
  • Use this command to look for a mount for the root directory:
    mount | grep " / "
  • You should be able to discover the device that is mounter there.
    In my case this is /dev/sda1

Adding a mount

  • Create a new directory under the current directory:
1cd
2mkdir myroot
  • Mount your device there:
1sudo mount /dev/sda1 ./myroot/
  • Go to this directory and look around:
1cd myroot
2ls

(use pwd to see that you are not dreaming):

1pwd
  • Amazing.
    now remove your new mount:
1cd ..
2sudo umount /dev/sda1 ./myroot