DevOps Commands Cheat Sheet by M Nagasai
Table of Contents
• Basic Navigation and File Management
• pwd – Print Working Directory
• ls – List Directory Contents
• cd – Change Directory
• cat – Concatenate and Display Files
• mkdir , rmdir , cp , mv , rm , touch , ln – Other File/Directory Commands
• Permissions and Ownership
• chmod – Change File Permissions
• chown – Change File Owner
• chgrp – Change File Group
• umask – Default Permission Mask
• System Information and Monitoring
• top – Interactive Process Viewer
• ps – Report Process Status
• free – Display Memory Usage
• df – Disk Free Space
• du – Disk Usage of Files/Directories
• uptime – System Uptime
• who , w , id , uname – Other Info Commands
• Networking
• ping – Test Network Connectivity
• ip – Show/Manipulate Network Configuration
• netstat , ss – Network Connections and Statistics
• traceroute – Trace Network Path
• nslookup , dig – DNS Query Tools
• curl , wget – HTTP/FTP Clients
• route – Kernel Routing Table
• Searching and Text Processing
• grep – Search Text via Patterns
• sed – Stream Editor for Text
• awk – Pattern Scanning and Processing
• find – Search for Files
• sort , uniq , cut , wc – Text Filtering Utilities
• diff , cmp – File Comparison
• tr – Translate or Delete Characters
• Package Management
• apt (Debian/Ubuntu) – Install/Remove Packages
• yum / dnf (CentOS/RHEL) – Install/Update Packages
1
• rpm (RPM packages) – Query/Install RPMs
• dpkg (Debian packages) – Query/Install DEBs
• snap – Universal Linux Packages
• User Management
• useradd , usermod , userdel – Create/Modify/Delete Users
• groupadd , groupdel – Create/Delete Groups
• passwd – Change User Password
• whoami , id , sudo , su – User Identity and Privilege Commands
• Automation and Scheduling
• cron , crontab – Recurring Task Scheduler
• at – One-time Task Scheduler
• File Compression and Archiving
• tar – Archive and Compress Files
• gzip , gunzip – Gzip Compression
• bzip2 , bunzip2 – Bzip2 Compression
• zip , unzip – Zip Archive Utility
• xz – XZ Compression (LZMA2)
• 7z – 7-Zip (LZMA) Compression
• Remote Access and File Transfer
• ssh – Secure Shell (Remote Login)
• scp – Secure Copy (Files over SSH)
• sftp – Secure FTP (Interactive over SSH)
• rsync – Remote and Local File Sync
• System Administration
• systemctl – Control Systemd Services
• journalctl – View Systemd Logs
• shutdown , reboot – Halt or Restart System
• mount – Mount/Unmount Filesystems
• DevOps and Cloud Tools
• docker – Docker Container Management
• kubectl – Kubernetes CLI
• terraform – Infrastructure as Code CLI
• ansible – Automation Engine CLI
• aws – AWS CLI
• gcloud – Google Cloud SDK CLI
• Version Control
• git – Distributed Version Control
• Bash Scripting Basics
• echo , read – Output and Input in Scripts
• if , for , while , case , test – Control Structures
2
Basic Navigation and File Management
pwd
Purpose & Description: The pwd (print working directory) command displays the absolute path of the
current directory
Syntax: pwd
. It’s commonly used to confirm your present location in the filesystem hierarchy.
1
Options: By default pwd shows the full path. With -L or -P you can print logical or physical paths
(resolving symlinks) if needed.
Example: Running pwd might output something like /home/user/projects
1
, indicating you are in
the projects subdirectory.
Tip: Use echo $(pwd) to include the path in strings or scripts.
Interview Q: What does pwd do? – It prints the working directory (current directory path)
1
.
ls
Purpose & Description: The ls command lists files and directories. By default, it shows non-hidden items
in the current directory 2 . It’s one of the most frequently used commands for directory navigation.
Syntax: ls [options] [file_or_directory] 2
Common Options:
- -l : long listing (shows permissions, owner, size, date)
- -a : include hidden files (starting with . )
- -h : human-readable sizes (e.g. 1K, 234M)
- -t : sort by modification time
- -r : reverse order
For example, ls -lha shows all files (including hidden) with detailed info in human-readable sizes
3
.
Example: ls -l /var/log might output lines like:
-rw-r--r-- 1 root root 12345 May 12 08:23 syslog
drwxr-xr-x 2 syslog adm
4096 May 12 08:00 apt
(Note: example output for illustration; actual may vary.)
Complex Breakdown: You can combine flags, e.g. ls -ltr sorts by time, oldest first.
Interview Q: How do you view hidden files using ls ? – Use ls -a , which shows all files including those
starting with a dot
3
.
cd
Purpose & Description: The cd command changes the shell’s current working directory. For example,
cd /etc moves you into the /etc directory
Syntax: cd [directory]
4
.
4
Options: Typically none; cd - switches to the previous directory.
Example: cd ~/projects followed by pwd might show /home/user/projects .
Tip: cd ~ or just cd returns you to the home directory.
3
cat
Purpose & Description: cat concatenates and displays file contents
text files or combine files.
Syntax: cat [options] [file]...
5
. Commonly used to view short
5
Options:
- -n : number all output lines
- -b : number non-blank lines
- -A : display non-printing chars (e.g. newline as $ )
Example: cat file.txt prints the content of file.txt .
Tip: Use cat file1 file2 > combined to merge files.
Other Basic Commands ( mkdir , rmdir , cp , mv , rm , touch , ln )
• mkdir : Create directories. Syntax: mkdir [options] directory_name
6
. For example,
mkdir mydir makes a new folder. Use -p to create parent directories as needed.
• rmdir : Remove empty directories. Syntax: rmdir directory_name
empty.
• cp : Copy files or directories
8
7
. Errors if directory is not
. Syntax: cp [options] source target . Use -r to copy
directories recursively. E.g. cp -r dir1 backup_dir .
• mv : Move or rename files/directories
9
. Syntax: mv [options] source target . Use to
rename (e.g. mv old.txt new.txt ) or move to a different folder.
• rm : Remove files or directories 10 . Syntax: rm [options] file . Use -r to remove directories
recursively. Warning: rm -rf forces deletion without prompt, use with caution.
• touch : Create an empty file or update timestamp. Syntax: touch file . For example, touch
newfile.txt creates a blank file if it doesn’t exist.
• ln : Create links. Syntax: ln [options] source link_name . ln file link makes a hard
link; ln -s file link makes a symbolic link.
Each of these basic commands may be cited and explored similarly (refer to general Linux documentation
for details).
Permissions and Ownership
chmod
Purpose & Description: chmod changes file and directory permissions 11 . It uses a numeric mode or
symbolic letters (r, w, x).
Syntax: chmod [options] mode file_or_directory
11
Options:
- u/g/o/a : user/group/others/all (as symbolic mode)
- +/- : add or remove permissions
- -R : recursive into directories
For example, chmod 755 script.sh gives owner read/write/execute and others read/execute.
Complex Example: Symbolically, chmod u+r,g-w,o=x file adds read to user, removes write for group,
sets others to execute.
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Interview Q: What does chmod 644 file.txt do? – Sets permissions to owner read/write, group read,
others read (no execute) 11 .
chown
Purpose & Description: chown changes file owner (and optionally group) 12 . Useful when transferring
files between users.
Syntax: chown [options] [new_owner][:new_group] file_or_directory
Example: sudo chown bob file.txt changes owner to user bob
13 . Add
12
:staff to change group
too.
Tip: Use chown -R user:group /dir to recursively change ownership of a directory.
chgrp
Purpose & Description: chgrp changes the group ownership of a file or directory 14 . It is similar to
chown but only for groups.
Syntax: chgrp [options] group file_or_directory
15
Example: sudo chgrp developers project.txt makes the file’s group developers .
umask
Purpose & Description: umask sets the default permission mask for new files/directories. It defines
permissions that should not be given. For example, a umask of 022 ensures new files are not writable by
group/others. It’s often used in shell profiles to enforce secure defaults 16 .
Syntax: umask [option] [mask] 16
Example: umask 027 makes new files readable by owner and group, but not by others.
System Information and Monitoring
top
Purpose & Description: top provides an interactive real-time view of running processes 17 . It shows
CPU/memory usage, process IDs, etc.
Syntax: top 17
Options: In top , press keys like M to sort by memory, P by CPU. -n option can make it non-interactive
for a given number of iterations.
Example: Running top on a busy server shows processes ordered by CPU usage, updating every few
seconds.
Interview Q: How can you exit top ? – Press q to quit.
ps
Purpose & Description:
ps
reports snapshot of current processes 18 . Without options, it shows
processes for the current shell.
Syntax: ps [options] 18
Common Options:
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- -e or -A : show all processes.
- -f : full format (shows PPID, start time).
- -u user : show processes for a user.
For example, ps -ef lists all processes with details, similar to ps -aux .
Example: ps -u nginx shows processes owned by user nginx .
Interview Q: Difference between ps -ef and ps aux ? – Both list all processes; -ef is standard syntax,
aux is BSD style (with x including processes without controlling TTY) 18 .
free
Purpose & Description: free displays system memory (RAM and swap) usage 19 . It shows total, used,
and free memory.
Syntax: free [options]
Options: -h for human-readable (shows MB/GB) is common.
Example: free -h might output:
Mem:
Swap:
total
7.8G
2.0G
used
2.1G
0B
free
3.5G
2.0G
shared
200M
buff/cache
2.2G
available
5.1G
This shows RAM and swap status.
df
Purpose & Description: df shows free and used disk space for mounted filesystems 20 . Useful to check
if a disk/partition is full.
Syntax: df [options] [filesystem_or_directory]
20
Common Options:
- -h : human-readable sizes (e.g. 1K, 234M, 2G) 20 .
- -T : show filesystem type.
Example: df -h /home might show:
Filesystem
/dev/sda1
Size
100G
Used Avail Use% Mounted on
40G
60G 40% /home
This indicates /home has 60GB free.
du
Purpose & Description: du (disk usage) shows the space used by files and directories 21 . It’s often used
to find large directories.
Syntax: du [options] [path]
21
Common Options:
- -h : human-readable sizes
6
- -s : summarize total for each argument (instead of each subdir)
- -c : produce a grand total.
Example: du -sh /var/log might output 1.2G
/var/log , meaning the log directory uses
1.2GB 21 .
uptime
Purpose & Description: uptime shows how long the system has been running, number of users, and
load averages 22 .
Syntax: uptime
Example: uptime could output:
09:30:01 up 5 days,
3:12,
2 users,
load average: 0.15, 0.10, 0.05
This means the system’s been up 5 days, 3 hours 12 mins, with a low load.
Other Information Commands ( who , w , id , uname )
• who : Lists logged-in users and their login terminals/time. For example, who might show user1
pts/0 2025-05-13 09:00 (10.0.0.1) . It helps see who is on the system.
• w : Similar to who but shows what each user is doing (processes), plus system load. It’s a more
detailed view of user activity 23 .
• id : Prints user identity (UID, GIDs) for current or specified user 24 . E.g., id bob might show
uid=1001(bob) gid=1001(bob) groups=1001(bob),27(sudo) . Useful for scripts to check
privileges.
• uname : Shows system information. uname -a prints kernel name, hostname, kernel version,
architecture, etc 25 . E.g., Linux myhost 5.15.0-50-generic x86_64 .
Networking
ping
Purpose & Description: ping tests network reachability between hosts. It sends ICMP echo requests to a
host and waits for replies 26 . Useful for checking if a server is up or the network is working.
Syntax: ping [options] destination 26
Options: -c count to send a fixed number of packets (e.g. ping -c 4 google.com ).
Example: ping -c 3 8.8.8.8 might output statistics showing bytes, RTT (round-trip time), packet loss.
If packets come back, the host is reachable.
ip
Purpose & Description: ip is the modern replacement for older tools like ifconfig and route . It
shows and configures network interfaces, IP addresses, routes, etc 27 .
Syntax: ip [options] OBJECT [command] 27 , where OBJECT can be addr , link , route , etc.
Examples:
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- ip addr show lists all network interfaces and their IP addresses.
- ip link set eth0 up brings interface eth0 up (enabled).
- ip route shows the routing table.
This powerful command can do almost everything about network config.
netstat , ss
Purpose & Description: netstat (deprecated on some systems) and ss show network connections and
listening ports.
- ss : The modern tool to display socket connections (replacing netstat ). For example, ss -tulpn
lists listening TCP/UDP ports and associated processes. It’s very fast.
- netstat : Older tool; netstat -tulpn shows similar info.
These are essential for troubleshooting open ports, network services, etc 28 .
traceroute
Purpose & Description: traceroute traces the path packets take to a remote host, listing all hops
(routers) along the way. It’s useful for diagnosing where network delays or failures occur 29 .
Syntax: traceroute [options] destination
Example: traceroute example.com might output each hop’s IP and latency. If it stops somewhere, that
router might be blocking or down.
Tip: On some systems the command is tracert (Windows) or requires traceroute package.
nslookup and dig
Purpose & Description: These are DNS lookup tools:
- nslookup : Queries DNS to find IP for a hostname or vice versa, using interactive or single-query mode
30 . E.g.,
nslookup linuxfoundation.org shows its IP address.
- dig : A more modern and detailed DNS query tool 31 . For example, dig +short google.com returns
Google’s IPs.
They help troubleshoot DNS issues by showing how names resolve.
curl and wget
Purpose & Description: curl and wget are command-line tools to download or transfer data over
network protocols (HTTP, FTP, etc.).
- curl is versatile for web APIs and supports many protocols. It can display output or save to file. “curl is a
powerful command-line tool for transferring data with URLs... one of the supported protocols (HTTP, HTTPS, FTP,
etc.)” 32 . Example: curl -O http://example.com/file.zip downloads a file.
- wget is primarily for non-interactive downloading of files from web/FTP. “wget (WWW get) is used to
download files from the Internet...” 33 . Example: wget http://example.com/file.zip .
Both support resuming downloads, recursive download, and are essential for retrieving resources.
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route
Purpose & Description: The route command (legacy) displays or modifies the kernel’s IP routing table
34 .
For example, route -n shows how packets will be routed. On newer systems, ip route is
preferred (as part of ip tool).
Example: route -n might output default gateway (e.g. 0.0.0.0
192.168.1.1 ), indicating
where non-local traffic is sent.
Searching and Text Processing
grep
Purpose & Description: grep searches text using patterns (regular expressions) within files or input. It’s
extremely common for filtering output 35 .
Syntax: grep [options] pattern [file...]
35
Common Options:
- -i : case-insensitive
- -r : recursive through directories
- -v : invert match (show non-matching lines)
- -n : show line numbers
Example: grep -i "error" /var/log/syslog finds all lines containing “error” (case-insensitive).
sed
Purpose & Description: sed is a stream editor used to perform basic text transformations on an input
stream (files or piped data) 36 . It can substitute, delete, insert, or replace text.
Syntax: sed [options] script [file]
Common Usage: sed 's/old/new/' file.txt replaces first occurrence of “old” with “new” on each
line. With -i , edits in place. It’s very powerful for scripting and batch edits.
awk
Purpose & Description: awk is a scripting language designed for text processing and reporting 37 . It
operates on fields.
Syntax: awk 'pattern { action }' [file]
Example: awk '{ print $1 }' data.txt prints the first column of each line of data.txt . Often
used to extract or compute fields from text.
find
Purpose & Description: find searches the filesystem for files/directories matching criteria. It can filter by
name, type, date, size, and perform actions on matches 38 .
Syntax: find [path...] [conditions] [actions] 38
Example: find / -type f -name "*.conf" lists all .conf files. You can also -exec another
command on each found item.
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Text Utilities: sort , uniq , cut , wc
• sort : Sort lines of text. E.g., sort data.txt sorts alphabetically. With -n numeric sort, -r
reverse. Useful for ordering data 39 .
• uniq : Filter or count duplicate lines (only adjacent duplicates). Often used after sort . E.g.,
sort list.txt | uniq removes duplicate lines 40 .
• cut : Extract columns or fields. E.g., cut -d: -f1 /etc/passwd prints usernames (delimiter
: ). It can cut by byte position or character as well 41 .
• wc : Word/line count. wc -l file counts lines, -w words, -c bytes. Example: wc -l /var/
log/syslog might output 12345 , showing number of lines. It’s often piped after grep to count
matches.
Compare Commands: diff , cmp
• diff compares two files line by line 42 , showing differences. Syntax: diff file1 file2 . It
outputs context of changes. Good for seeing what changed between versions.
• cmp compares files byte by byte 43 . If files differ, it reports the first difference. If no output, files
are identical. Less human-readable than diff , but useful in scripts to check equality.
Example: diff old.txt new.txt might show lines prefixed with < (from old) and > (from
new).
tr
Purpose & Description: tr (translate) translates or deletes characters from input 44 . It reads from stdin
and writes to stdout.
Syntax: tr [options] SET1 [SET2]
Example:
echo
"Hello
World"
|
tr
'[:upper:]'
'[:lower:]'
converts to lowercase. Or
tr -d ' ' < file removes spaces. It’s used in pipelines to clean or reformat text.
Package Management
apt / apt-get (Debian/Ubuntu): Used to install, update, and remove DEB packages. E.g., sudo apt
update then sudo apt install nginx . It handles dependencies.
yum / dnf (CentOS/RHEL/Fedora): Similar, for RPM-based distros. E.g., sudo yum install httpd .
rpm : Low-level RPM package manager (query or install single packages).
dpkg : Low-level Debian package tool ( dpkg -i file.deb ).
snap : Canonical’s universal package system ( sudo snap install package ).
For example, on Ubuntu, sudo apt install docker.io installs Docker. On CentOS, sudo yum
install docker-ce . The choice depends on distro 45 .
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User Management
useradd , usermod , userdel
• useradd : Create a new user. For example, sudo useradd -m alice creates user alice with a
home directory 46 .
• usermod : Modify user properties (e.g., change home directory, add to group). E.g.,
sudo usermod -aG sudo alice adds alice to sudo group.
• userdel : Delete a user. E.g., sudo userdel -r bob removes user bob and their home
directory 47 .
groupadd , groupdel
• groupadd : Create a new group. Example: sudo groupadd developers
• groupdel : Remove a group. E.g., sudo groupdel developers
48 .
49 . Useful for managing
permissions.
passwd
Purpose: Change user password. For example, passwd alice prompts to set a new password for user
alice
50 . Only root or the user themselves can change it.
Syntax: passwd [user]
50 . Without arguments, changes current user’s password.
whoami , id , sudo , su
• whoami : Prints effective user name. Simply whoami outputs your username 51 . Handy in scripts
to confirm user identity.
• id : Shows current user’s UID and groups 24 (already mentioned).
• sudo : Run a command as root (or another user) 52 . Prefix any command with sudo to execute
with elevated privileges. For example, sudo apt update . Requires user to be in sudoers .
• su : Switch user. E.g., su - switches to root (asks for root password). su alice switches to user
alice. (Less used now in distributions favoring sudo .)
Automation and Scheduling
cron and crontab
Purpose & Description: Cron is the system service that runs scheduled tasks. crontab is the utility to
schedule jobs (scripts or commands) at specified times 53 .
Syntax: Cron jobs use a time format: MIN HOUR DAY MONTH DOW command . For example, 0 2 * * * /
usr/local/bin/backup.sh runs daily at 2am.
Example: To edit your cron jobs: crontab -e and add a line like 30 1 * * * /path/to/script.sh .
This uses the Cron daemon to automate repetitive tasks (backups, updates, etc.) 53 .
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at
Purpose: The at command schedules a one-time task at a specified future time. For example, echo "/
path/to/script.sh" | at 03:00 schedules it at 3am. (Caveat: must have the at daemon running.) It’s
used for ad-hoc scheduling when cron (recurring) is not needed.
File Compression and Archiving
tar
Purpose & Description: tar creates and manipulates archive files (tarballs) 54 . It can also compress/
decompress archives.
Syntax: tar [options] archive_name files...
54
Common Usage:
- Create: tar czf archive.tar.gz directory/ (create gzip-compressed tar)
- List: tar tzf archive.tar.gz (list contents)
- Extract: tar xzf archive.tar.gz (extract).
Example: tar cf logs.tar /var/log/*.log makes an uncompressed archive. Add -z for gzip or j for bzip2.
Tip: The ‘z’, ‘j’, ‘J’ options for gzip, bzip2, xz, respectively.
gzip / gunzip
Purpose: Compress ( gzip ) or decompress ( gunzip ) files.
Syntax: gzip [options] file (replaces file with .gz file) 55 . gunzip file.gz restores it.
Example: gzip file.txt creates file.txt.gz and deletes original (default) 55 . Use gzip -k
file.txt to keep the original 56 .
bzip2 / bunzip2
Purpose: Higher compression tool than gzip.
Syntax: bzip2 file compresses file into file.bz2 , deleting original 57 . bunzip2 file.bz2
restores it.
Example: bzip2 -z data.csv compresses to data.csv.bz2
57 .
The -k option can keep the
original file.
zip / unzip
Purpose: Create ( zip ) or extract ( unzip ) zip archives.
Description: “zip command compresses files into a .zip archive, saving disk space and combining files” 58 .
Syntax: zip [options] archive_name.zip files... 59 . For example, zip mydocs.zip *.txt .
unzip : Extract. Syntax: unzip archive_name.zip
60 .
Example: zip -r backup.zip /home/user/ recursively zips a directory. unzip backup.zip extracts
it. Zip is cross-platform (Windows/Mac can open zip files).
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xz
Purpose & Description:
xz
compresses files using the LZMA2 algorithm, often yielding higher
compression.
Syntax: xz file produces file.xz . Use xz -d file.xz or unxz to decompress.
Example: xz -z largefile compresses largefile to largefile.xz . The -k option keeps
original. (Famous for high compression in distributions, e.g. Linux kernel tarballs.)
7z
Purpose: 7z (from p7zip) is another high-compression tool (supports .7z archives, gzip, bzip2, etc.).
Usage: For example, 7z a archive.7z files... creates an archive. 7z x archive.7z extracts. It’s
not installed by default on all Linux, but often used in DevOps contexts.
Remote Access and File Transfer
ssh
Purpose & Description: ssh (Secure Shell) opens a secure encrypted terminal session on a remote
machine 61 . It also tunnels and transfers data.
Syntax: ssh [options] user@hostname .
Example: ssh alice@192.168.1.10 logs in as alice to that host. It uses encryption so your password/
traffic is secure.
Tip: Use SSH keys ( ssh-keygen ) for passwordless login. SSH also provides port forwarding (tunneling).
scp
Purpose & Description: scp (Secure Copy) transfers files securely over SSH 62 . It is basically “SSH for file
transfer”.
Syntax: scp [options] source user@host:dest or vice versa.
Example: scp /path/to/file.txt user@remote:/path/ copies file to remote. scp user@remote:/
path/file . pulls from remote.
Complex Example: Recursive copy: scp -r /local/dir user@remote:/dest copies entire directory.
Interview Q: How is scp different from ftp ? – scp encrypts all data (files and credentials) over SSH 62 ,
whereas FTP is unencrypted by default.
sftp
Purpose: sftp is an interactive file transfer program over SSH (like FTP but secure) 63 .
Usage: Run sftp user@host , then use commands like ls , get , put to transfer files. It’s often used
by scripts or users who prefer an FTP-like interface but with SSH security.
rsync
Purpose & Description:
efficiently
rsync
synchronizes files/directories between local and remote systems
64 . It uses a smart algorithm to transfer only differences, saving bandwidth.
13
Syntax: rsync [options] source destination
Example: rsync -avz /home/user/ alice@server:/backup/ copies /home/user/ to /backup/
on remote host, preserving attributes ( -a ) and compressing data ( -z ). It can resume partial transfers.
Interview Q: Why use rsync over scp? – Because rsync transfers only the changed blocks (delta transfer)
making it faster for incremental backups 64 .
System Administration
systemctl
Purpose & Description: systemctl controls the systemd init system, managing services and system
states 65 .
Syntax: systemctl [command] [unit] .
Common Commands:
start ,
stop ,
restart ,
enable
(at boot),
status . For example,
systemctl start nginx starts the nginx service; systemctl status sshd shows its status.
Example: systemctl enable httpd configures Apache to start on boot.
journalctl
Purpose & Description: journalctl views and queries the systemd journal (centralized logs) 66 . It’s
used to inspect system and service logs.
Syntax: journalctl [options] .
Usage: journalctl -u sshd shows logs for sshd service. journalctl -b shows current boot’s logs.
Example: journalctl -xe shows recent logs with priority error (useful for debugging failures).
shutdown , reboot
Purpose & Description:
- shutdown halts or powers off the machine safely 67 . It notifies users and processes, then brings the
system down.
- reboot is equivalent to shutdown -r now , rebooting the system immediately.
Syntax: shutdown [OPTIONS] [TIME] [MESSAGE]
67 . E.g.
shutdown -h now halts immediately,
shutdown +10 "Maintenance" schedules a shutdown in 10 minutes. Only root can execute.
Interview Q: How to cancel a scheduled shutdown? – Use shutdown -c
68 .
mount
Purpose & Description: Attach filesystems to the directory tree 69 . For example, mounting a USB drive at
/mnt/usb .
Syntax: mount -t type device directory (or see /etc/fstab).
Example: mount /dev/sdb1 /mnt/usb mounts the device. df -h can then show /mnt/usb usage.
Unmount: Use umount /mnt/usb to safely detach.
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DevOps and Cloud Tools
docker
Purpose: CLI for managing Docker containers and images. E.g., docker run nginx starts an Nginx
container. Other subcommands:
docker
build ,
docker
ps ,
docker
exec , etc. (No citation
available.)
kubectl
Purpose: Kubernetes command-line tool. Controls Kubernetes clusters. E.g., kubectl get pods lists
pods. Other commands: apply , describe , logs , etc. (Configuration for K8s.)
terraform
Purpose & Description: terraform is the CLI for HashiCorp Terraform (Infrastructure as Code). “The
command line interface to Terraform is the
subcommands…”
Usage: Key commands include
terraform
command, which accepts a variety of
70 .
terraform
apply
terraform
init ,
plan ,
creates infrastructure as defined in
.tf
apply ,
destroy . For example,
files. It manages cloud resources
declaratively.
ansible
Purpose: CLI for Ansible automation. For ad-hoc tasks use ansible , for playbooks use ansibleplaybook . It automates configuration management across servers.
aws (AWS CLI)
Purpose: AWS command-line interface. Prefix AWS service commands, e.g., aws s3 ls to list S3 buckets.
It allows scripting of AWS service actions from shell.
gcloud (Google Cloud CLI)
Purpose: Google Cloud SDK CLI. E.g., gcloud compute instances list to list VMs. Manages GCP
resources from terminal.
(Details for these tools depend on their documentation; included here for completeness.)
Version Control
git
Purpose & Description: Git is a distributed version control system. It tracks changes in files and
coordinates work among developers. Commands include git clone , git commit , git push , etc.
For example, git commit -m "message" commits staged changes. (No citation used; well-known tool.)
15
Bash Scripting Basics
echo
Purpose & Description: echo prints text or variables to the screen 71 . It’s used in scripts to output
messages or results.
Syntax: echo [options] [string]
Example:
echo
"Hello,
$USER!"
71 .
might output
Hello,
alice! . Using
echo
-e
enables
interpreting backslashes (e.g. \n newline) 72 .
read
Purpose: Reads a line from standard input into a variable. Common in scripts for interactive input.
Syntax: read [options] variable . For example:
read -p "Enter your name: " NAME
echo "Hello, $NAME!"
prompts and reads user input into $NAME .
if , for , while , case , test
These are shell control structures (not separate executables):
- if / then / fi : Conditional execution. Example: if [ -f file ]; then echo "exists"; fi .
- for / do / done : Loop over items. Example: for file in *.txt; do echo "$file"; done .
- while / do / done : Loop with a condition. Example: while read line; do echo $line; done <
file .
- case / esac : Pattern matching. Example: case "$var" in hello) echo Hi;; *) echo Bye;;
esac .
- [ (test): Builtin to evaluate expressions. E.g. [ "$a" -gt 5 ] tests numeric comparison. Often used
in if .
These constructs form the basis of bash scripting logic.
Note: This cheat sheet summarizes common commands with examples. In practice, always refer to each
command’s --help or manual ( man ) for full syntax and options. The Q&A sections highlight typical
interview questions one might encounter about these commands.
Sources: Official documentation and tutorials on Linux commands 1 3 11 14
53
54
55
58
63
62
64
50
71 and related references in the Linux community.
16
22
73
23
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20
21
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2
4
5
6
7
8
9
10
11
12
13
17
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27
33
35
38
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50
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52
Linux Commands All Users Should Know {Ultimate List}
https://phoenixnap.com/kb/linux-commands
3
Linux "ls" Command with Examples
https://www.atatus.com/blog/ls-command-in-linux-with-example/
14
15
chgrp command in Linux with Examples | GeeksforGeeks
https://www.geeksforgeeks.org/chgrp-command-in-linux-with-examples/
16
Umask command in Linux with examples | GeeksforGeeks
https://www.geeksforgeeks.org/umask-command-in-linux-with-examples/
19
Classic SysAdmin: Linux 101: 5 Commands for Checking Memory Usage in Linux - Linux Foundation
https://www.linuxfoundation.org/blog/blog/classic-sysadmin-linux-101-5-commands-for-checking-memory-usage-in-linux
22
Linux Uptime Command: Syntax, Options, Examples
https://phoenixnap.com/kb/linux-uptime
23
w Command in Linux with Examples {+Options & Syntax}
https://phoenixnap.com/kb/w-command-in-linux
24
id command in Linux with examples | GeeksforGeeks
https://www.geeksforgeeks.org/id-command-in-linux-with-examples/
28
SS Command In Linux {With Examples} | phoenixNAP KB
https://phoenixnap.com/kb/ss-command
29
Traceroute command and its options - ClouDNS Blog
https://www.cloudns.net/blog/traceroute-command-tracert/
30
How to Use the nslookup Command {10 Examples}
https://phoenixnap.com/kb/nslookup-command
31
dig Command in Linux with Examples | GeeksforGeeks
https://www.geeksforgeeks.org/dig-command-in-linux-with-examples/
Top 10 curl command options. curl is a powerful command-line tool… | by Bhupesh Choudhary |
Medium
32
https://medium.com/@bhaibhupesh10/top-10-curl-command-options-edb0cac3fb8e
34
6 Deprecated Linux Commands and Alternative Tools for Linux
https://www.tecmint.com/deprecated-linux-commands/
36
Sed Command in Linux/Unix With Examples | GeeksforGeeks
https://www.geeksforgeeks.org/sed-command-in-linux-unix-with-examples/
37
AWK command in Unix/Linux with examples | GeeksforGeeks
https://www.geeksforgeeks.org/awk-command-unixlinux-examples/
39
Linux sort Command with Examples
https://phoenixnap.com/kb/linux-sort
40
Uniq Command - Remove Duplicate Lines from a Linux Files
https://www.tecmint.com/remove-duplicate-lines-linux-files/
17
54
41
cut command in Linux with examples | GeeksforGeeks
https://www.geeksforgeeks.org/cut-command-linux-examples/
43
cmp Command in Linux with examples | GeeksforGeeks
https://www.geeksforgeeks.org/cmp-command-in-linux-with-examples/
44
tr command in Unix/Linux with examples | GeeksforGeeks
https://www.geeksforgeeks.org/tr-command-in-unix-linux-with-examples/
48
49
How to create, delete, and modify groups in Linux
https://www.redhat.com/en/blog/linux-groups
53
‘crontab’ in Linux with Examples | GeeksforGeeks
https://www.geeksforgeeks.org/crontab-in-linux-with-examples/
55
56
Gzip Command in Linux | GeeksforGeeks
https://www.geeksforgeeks.org/gzip-command-linux/
57
How to Compress and Decompress a .bz2 File in Linux
https://www.tecmint.com/linux-compress-decompress-bz2-files-using-bzip2/
58
59
60
ZIP command in Linux with examples | GeeksforGeeks
https://www.geeksforgeeks.org/zip-command-in-linux-with-examples/
61
SSH command usage, options, and configuration in Linux/Unix
https://www.ssh.com/academy/ssh/command
62
How to Securely Copy Files in Linux | scp Command | GeeksforGeeks
https://www.geeksforgeeks.org/scp-command-in-linux-with-examples/
63
SSH File Transfer Protocol (SFTP): Secure File Transfer Protocol
https://www.ssh.com/academy/ssh/sftp-ssh-file-transfer-protocol
64
Rsync by examples - A fast and versatile file copying tool.
https://overwriteit.com/rsync-by-examples-a-fast-and-versatile-file-copying-tool/
65
Manage Systemd Services with systemctl on Linux | DigitalOcean
https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units
66
How To Use Journalctl to View and Manipulate Systemd Logs | DigitalOcean
https://www.digitalocean.com/community/tutorials/how-to-use-journalctl-to-view-and-manipulate-systemd-logs
67
68
shutdown command in Linux with Examples | GeeksforGeeks
https://www.geeksforgeeks.org/shutdown-command-in-linux-with-examples/
69
Linux mount Command with Examples {+How to Unmount a File System}
https://phoenixnap.com/kb/linux-mount-command
70
Terraform CLI overview | Terraform | HashiCorp Developer
https://developer.hashicorp.com/terraform/cli/commands
71
72
echo command in Linux with Examples | GeeksforGeeks
https://www.geeksforgeeks.org/echo-command-in-linux-with-examples/
73
who Command in Linux: Syntax, Options, Examples
https://phoenixnap.com/kb/linux-who-command
18