Linux System and Disk Commands for DevOps Engineers¶

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In this section, you will learn basic system, memory, disk, and navigation commands commonly used by DevOps engineers while monitoring servers and troubleshooting production issues.

`free` – Check Memory Usage¶

Used to check RAM / memory usage on a Linux server.

By default, the free command shows memory usage in kilobytes (KB).

ubuntu@manikandan:~$ free
               total        used        free      shared  buff/cache   available
Mem:          987264      334996       85924        1304      566344      472600
Swap:              0           0           0

`free -h` (Human Readable)¶

The -h option displays memory usage in MB or GB.

ubuntu@manikandan:~$ free -h
               total        used        free      shared  buff/cache   available
Mem:           964Mi       327Mi        82Mi       1.0Mi       553Mi       461Mi
Swap:             0B          0B          0B

`df` – Check Disk Usage¶

Used to check disk usage on a Linux server.

By default, df displays disk usage in kilobytes (KB).

ubuntu@manikandan:~$ df
Filesystem     1K-blocks    Used Available Use% Mounted on
tmpfs              98728    1276     97452   2% /run
/dev/sda1       47143192 7437908  39688900  16% /
tmpfs             493632       0    493632   0% /dev/shm
tmpfs               5120       0      5120   0% /run/lock
/dev/sda15        106858    6182    100677   6% /boot/efi
tmpfs              98724       4     98720   1% /run/user/1001

`df -h` (Human Readable)¶

ubuntu@manikandan:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs            97M  1.3M   96M   2% /run
/dev/sda1        45G  7.1G   38G  16% /
tmpfs           483M     0  483M   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
/dev/sda15      105M  6.1M   99M   6% /boot/efi
tmpfs            97M  4.0K   97M   1% /run/user/1001

Other Common Linux Utility Commands¶

`which`¶

Find the location of a command.

which kubectl

`man`¶

View the manual page of a command.

man df

`id`¶

Display user and group information.

id

`hostname`¶

Check the system hostname.

hostname

cd .. → Move one directory up
cd ../.. → Move two directories up
cd → Go to home directory
cd ~ → Go to home directory explicitly
cd - → Switch to previous directory

Practice Tasks¶

Check memory usage using free and free -h
Check disk usage using df -h
Identify which partition is mounted on /
Check the hostname of your server
Switch between two directories using cd -

🧠 Quick Quiz – System Basics¶

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Which command shows disk usage in a human-readable format?

📝 Want More Practice?¶

To strengthen your understanding and prepare for interviews, try the full 20-question practice quiz based on this chapter:

👉 Start System & Disk Commands Quiz (20 Questions)

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Linux System and Disk Commands for DevOps Engineers¶

free – Check Memory Usage¶

free -h (Human Readable)¶

df – Check Disk Usage¶

df -h (Human Readable)¶