Disk usage and management

1. df (Disk Filesystem Usage)

The df command displays the amount of disk space used and available on mounted filesystems.

Common Options:

-h → Human-readable format

-T → Shows file system type (e.g., ext4, xfs)

-i → Displays inode usage instead of disk space

1. To show the disk usage in human-readable format (MB/GB).

    df -h
   

   

2. To force the output to show sizes in KB/GB/MB.

   BM (mega bytes), BG(giga), BK (Kilobytes)

    df -h -BK
   

3. 

   To display file system

df -T

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2. du (Disk Usage)

It shows the size of files and directories.

Common Options:

-s → Shows total size of a directory

-h → Human-readable format

-c → Displays a total at the end of the output.

-a → Shows the size of all files (not just directories).

1. To displays total size of /home/user/ in a human-readable format.

    du -sh <directory-name>
   

   

   

2. For more granular info - files

    du -ah <filename>
   

   

3. To display a grand total

    du -ahc
   

   

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3. free

It is used to check system memory usage in Linux, including RAM and swap space.

1. Displays memory usage in bytes by default.

    free -h
   

   

2. To continuously monitor memory usage at regular intervals.

    free -s N
   

   The -s <seconds> option allows you to set the refresh rate.

   Keep refreshing memory after N sec

   

3. Exit after repeating N times

   

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   4. mount (Mount a Filesystem)

   The mount command attaches a storage device (e.g., USB, external drive) to a directory in the filesystem.

   1. To mount /dev/sdb1 (USB) to /mnt/usb.

       mount /dev/sdb1 /mnt/usb
      

      Common Options:

      mount -o ro /dev/sdb1 /mnt/usb → Mount in read-only mode

      mount -t ext4 /dev/sdb1 /mnt/usb → Mount with a specific filesystem type

2. To list all mounted filesystems:

    mount | column -t
   

   

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5. unmount (Unmount a Filesystem)

The umount command detaches a mounted filesystem.

1. To unmount the USB drive from /mnt/usb.

    umount /mnt/usb