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Practice Exercise: Understanding Filesystems

Objectives

  • Learn about filesystems and their importance in Linux.
  • Explore different types of filesystems used in Linux.
  • Understand how to check and manage filesystems.

Scenario

As a Linux enthusiast, you want to deepen your understanding of filesystems and how they play a crucial role in organizing and managing data on your Linux system. This exercise will help you gain insights into various filesystem types and how to interact with them.

Tasks

Task 1: Understanding Filesystems

  • Begin by researching and making a list of at least five different filesystems commonly used in Linux.
  • For each filesystem, note down its key features, advantages, and use cases.

Task 2: Checking the Current Filesystem

  • Open a terminal on your Linux system.
  • Use the df command to display information about the currently mounted filesystems.
  • Identify the root filesystem and note down its size, used space, and available space.
[intern@intern-a1t-inf-lnx1 ~]$ df
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/root       20568532 5187056  14316552  27% /
devtmpfs          480788       0    480788   0% /dev
tmpfs             484544       0    484544   0% /dev/shm
tmpfs             484544    6768    477776   2% /run
tmpfs             484544       0    484544   0% /sys/fs/cgroup
tmpfs              96908       0     96908   0% /run/user/1015
tmpfs              96908       0     96908   0% /run/user/1001

[intern@intern-a1t-inf-lnx1 ~]$ df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        20G  5.0G   14G  27% /

Task 3: Creating and Mounting a Filesystem

  • Create a new ext4 filesystem on a spare storage device /dev/sdb. You can use the mkfs.ext4 command.
  • Create a directory (e.g., /mnt/new_drive) to mount your new filesystem.
  • For this task to be possible we'll be needing to add another disk to our instance and use it to create a new filesystem
  • After adding another disk to the instance you can now run mkfs.ext4
  • Mount the new disk using mount
  • Confirm that it is now mounted using df

[intern@intern-a1t-inf-lnx1 ~]$ lsblk
NAME MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda    8:0    0   20G  0 disk /
sdb    8:16   0    1G  0 disk 
sdc    8:32   0  512M  0 disk

[intern@intern-a1t-inf-lnx1 ~]$ sudo mkfs.ext4 /dev/sdb
[sudo] password for intern:
mke2fs 1.46.5 (30-Dec-2021)
Discarding device blocks: done
Creating filesystem with 262144 4k blocks and 65536 inodes
Filesystem UUID: e45a2d40-bf51-4794-ba15-483a4e61ec90
Superblock backups stored on blocks:
    32768, 98304, 163840, 229376

Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

[intern@intern-a1t-inf-lnx1 ~]$ sudo mkdir /mnt/new_drive
[intern@intern-a1t-inf-lnx1 ~]$ sudo mount /dev/sdb /mnt/new_drive
[intern@intern-a1t-inf-lnx1 ~]$ df
Filesystem     1K-blocks    Used Available Use% Mounted on
devtmpfs            4096       0      4096   0% /dev
tmpfs             493376       0    493376   0% /dev/shm
tmpfs             197352    5412    191940   3% /run
/dev/sda        20568532 1244472  18259148   7% /
tmpfs              98672       0     98672   0% /run/user/1000
/dev/sdb          996780      24    927944   1% /mnt/new_drive
- As you can see the /dev/sdb is now mounted in /mnt/new_drive - Create a test file within your new filesystem: 
[intern@intern-a1t-inf-lnx1 ~]$ touch /mnt/new_drive/testfile
[intern@intern-a1t-inf-lnx1 ~]$ ls -lrt /mnt/new_drive/
total 16
drwx------. 2 root root 16384 Oct  1 23:22 lost+found
-rw-r--r--. 1 root root     0 Oct  1 23:24 testfile

Task 4: Modifying Filesystem Properties

  • Experiment with changing the properties of your mounted filesystem. You can try changing the filesystem label or resizing it (if it's on a loopback device).
[intern@intern-a1t-inf-lnx1 ~]$ sudo tune2fs -L "New Filesystem" /dev/sdb
[sudo] password for intern:
tune2fs 1.46.5 (30-Dec-2021)
[intern@intern-a1t-inf-lnx1 ~]$ sudo e2label /dev/sdb
New Filesystem

Task 5: Unmounting and Removing a Filesystem

  • Unmount the filesystem you created in Task 3 using the umount command.
  • Verify that the filesystem is no longer mounted using df.
  • If it was a loopback device, you can remove it using the losetup -d command. 
    [intern@intern-a1t-inf-lnx1 ~]$ sudo umount /mnt/new_drive
  • Run df to see if it was properly unmounted 
    [intern@intern-a1t-inf-lnx1 ~]$ df
Filesystem     1K-blocks    Used Available Use% Mounted on
devtmpfs            4096       0      4096   0% /dev
tmpfs             493376       0    493376   0% /dev/shm
tmpfs             197352    5412    191940   3% /run
/dev/sda        20568532 1244484  18259136   7% /
tmpfs              98672       0     98672   0% /run/user/1000
  • Check the test file you've created. Now that you have unmounted the filesystem, it should be gone, unless the filesystem will be remounted: 
    [intern@intern-a1t-inf-lnx1 ~]$ ls -l /mnt/new_drive/
total 0

Task 6: Checking and Repairing Filesystems

  • Use the fsck command to check the integrity of a filesystem (e.g., fsck /dev/sdb where /dev/sdb is your filesystem device).
  • Make sure that the device you are trying to check is unmounted 
    [intern@intern-a1t-inf-lnx1 ~]$ sudo fsck /dev/sdb
fsck from util-linux 2.37.4
  • No meaningful output here since the filesystem is healthy and there's nothing to be repaired

Conclusion

By completing this exercise, you've gained valuable insights into Linux filesystems, including their types, creation, modification, and maintenance. Understanding filesystems is crucial for managing data effectively on your Linux system.