Linux Basics: Commands You’ll Actually Use

Navigation

pwd            # show current directory
ls -la         # list all files (including hidden) with details
cd /path       # change directory
cd ..          # go up one folder
mkdir test     # create folder
touch file.txt # create empty file

Reading files

cat file.txt         # print entire file
less file.txt        # scroll through file
head -n 20 file.txt  # first 20 lines
tail -n 20 file.txt  # last 20 lines
grep -n "admin" file.txt  # search for "admin" with line numbers

Permissions (important for security)

Permissions are a core security concept. Learn them early: read (r), write (w), execute (x).

ls -l                 # view permissions
chmod 644 file.txt    # rw-r--r--
chmod 755 script.sh   # rwxr-xr-x
chown user:user file  # change owner and group

Processes

ps aux | head         # view processes
top                   # live process view
kill -9 PID           # kill a process by PID (use carefully)
whoami                # current user
id                    # user + groups

Networking checks

ip a                  # show interfaces + IPs
ip r                  # show routes
ss -tulpen            # show listening ports + processes
curl -I https://example.com  # fetch headers only
ping -c 4 8.8.8.8     # basic connectivity check

Finding things

find . -name "*.conf"         # find files by name
find / -perm -4000 2>/dev/null # find SUID binaries (advanced)
which python                  # locate a command
whereis ssh                   # find binary + docs

Pro tip: keep notes like a pro

Create a “commands.md” file and add what you use often. Your future self will thank you.