Common Linux commands

Replace example file and directory names with your actual paths.

Directories

Command	Action
pwd	Print current directory
ls	List directory entries
ls -lh	Detailed listing with readable sizes
ls -a	Include hidden entries
cd DIR	Enter a directory
cd ..	Go to parent directory
cd ~	Go home
mkdir DIR	Create a directory
mkdir -p a/b/c	Create nested directories

pwd
ls -lh
mkdir -p project/data
cd project

Copy, move, and delete

Command	Action
cp SOURCE DEST	Copy a file
cp -r SOURCE DEST	Copy a directory
mv SOURCE DEST	Move or rename
rm FILE	Delete a file
rm -r DIR	Delete a directory and its contents

cp input.txt input.bak
mv result.txt results/result.txt
rm temp.txt

Check before deleting

Files removed with rm are generally not recoverable through a simple undo. Verify the current and target paths before deleting.

View files

Command	Action
cat FILE	Print the entire file
less FILE	Page through a file; press q to quit
head FILE	First 10 lines
head -n 20 FILE	First 20 lines
tail FILE	Last 10 lines
tail -f FILE	Follow appended log output
wc -l FILE	Count lines

head -n 5 input.txt
tail -f job.out
wc -l samples.txt

Find files and text

Command	Action
find . -name "*.txt"	Find matching filenames below the current directory
find . -type f	Find regular files recursively
grep "TEXT" FILE	Find matching text
grep -n "TEXT" FILE	Include line numbers
grep -r "TEXT" DIR	Search recursively

find . -name "*.log"
grep -n "error" job.out

Archives

Command	Action
tar -czf data.tar.gz data/	Create a gzip-compressed archive
tar -xzf data.tar.gz	Extract it
zip -r data.zip data/	Create a ZIP archive
unzip data.zip	Extract ZIP

tar -czf results.tar.gz results/
tar -xzf results.tar.gz

Permissions

Command	Action
ls -l	Show permissions, owner, and size
chmod +x script.sh	Add executable permission
chmod 600 FILE	Owner read/write only
chmod 644 FILE	Owner read/write; others read-only

ls -l run.sh
chmod +x run.sh
./run.sh

Disk usage

Command	Action
df -h	Filesystem capacity and free space
du -sh DIR	Total directory usage
du -h --max-depth=1	Usage one level below the current directory
ls -lh	File sizes

du -sh project
du -h --max-depth=1
df -h

Processes

ps -u $USER lists your processes; top monitors processes interactively; kill PID signals a process to terminate.

ps -u $USER
kill 12345

Use the scheduler for long computations. Login nodes are for brief checks and file management.

Text editors

nano

nano run.sh

Ctrl+O saves, Enter confirms the filename, and Ctrl+X exits.

vim

vim run.sh

Press i to insert text and Esc to leave insert mode. Use :wq to save and quit, or :q! to quit without saving.

Common workflows

Create a project layout:

mkdir -p ~/project/data ~/project/scripts ~/project/results
cd ~/project

Follow job output or error logs:

tail -f job.out
tail -f job.err

Archive results:

tar -czf results.tar.gz results/

Find large directories and files:

du -h --max-depth=1
ls -lh

Prefer letters, digits, underscores, and hyphens in filenames. Check pwd and ls before important file operations. Read .out, .err, and application logs when scripts fail. Use COMMAND --help when unsure about an option.