Linux Cheat Sheet

Tab = autocomplete
Ctrl + R = reverse search command history
Ctrl + C = stop a running command
Ctrl + A / Ctrl + E = start/end of line
history = list past commands

man <cmd>            # full manual (q to quit)
<cmd> --help         # quick usage
info <cmd>           # alternative docs (often more structured)
which <cmd>          # where a command comes from
type <cmd>           # alias/function/builtin or file?
apropos <keyword>    # search manpages by keyword

pwd                 # where am I
ls                  # list files
ls -lah             # long + all + human sizes
cd /path            # change dir
cd ..               # up one
cd -                # back to previous dir
mkdir -p a/b/c      # create nested dirs
tree -L 2           # directory tree (if installed)

touch file.txt      # create/update timestamp
cp src dst          # copy
cp -r dir1 dir2     # copy directory
mv old new          # move/rename
rm file             # delete
rm -r dir           # delete directory
rm -rf dir          # force delete (danger)
cat file            # print file
less file           # view with paging (q quits, /search)
head -n 20 file     # first 20 lines
tail -n 20 file     # last 20 lines
tail -f file.log    # follow log output
stat file           # detailed metadata

find . -name "*.log"                 # find by name
find . -type f -mtime -7             # files modified in last 7 days
grep "needle" file                   # search text in file
grep -R "needle" .                   # recursive search
grep -RIn "needle" .                 # recursive + line numbers + ignore binary
rg "needle"                          # ripgrep (faster, if installed)

ln -s TARGET LINK              # create symlink
ln -sfn TARGET LINK            # replace existing symlink safely

ls -l LINK                     # show where it points
readlink LINK                  # print target path
readlink -f LINK               # resolve to final absolute path

rm LINK                        # remove symlink (doesn't delete target)
unlink LINK                    # same as rm for symlinks

find . -type l                 # list symlinks
find . -xtype l                # find broken symlinks

cp -a SRC DST                  # copy while preserving symlinks
cp -aL SRC DST                 # copy files symlinks point to (dereference)

cmd1 | cmd2          # pipe output into another command
cmd > out.txt        # write (overwrite)
cmd >> out.txt       # append
cmd 2> err.txt       # stderr to file
cmd > out.txt 2>&1   # stdout+stderr to same file
cmd < in.txt         # read file as input
tee out.txt          # write to file AND show on screen

ls -l                      # see permissions
chmod 644 file             # rw-r--r--
chmod +x script.sh         # make executable
chown user:group file      # change owner/group (sudo often needed)
sudo <cmd>                 # run as admin

ps aux | less              # list processes
top                        # live view (or htop if installed)
pgrep -a nginx             # find process by name
kill <pid>                 # ask process to stop
kill -9 <pid>              # force kill (last resort)
pkill -f "pattern"         # kill matching command line
cmd &                      # run in background
jobs                       # list background jobs
fg %1                      # bring job 1 to foreground
bg %1                      # resume job 1 in background
nice -n 10 cmd             # lower priority

df -h                      # disk usage by filesystem
du -sh *                   # size of each item in current dir
free -h                    # RAM usage
lsblk                      # block devices (disks/partitions)
mount | less               # mounted filesystems

tar -czf archive.tgz dir/      # create .tgz
tar -xzf archive.tgz           # extract .tgz
zip -r archive.zip dir/        # zip folder
unzip archive.zip              # unzip
gzip file                      # file.gz
gunzip file.gz                 # unzip gzip

ip a                       # show IPs (modern)
ip r                       # routes
ping -c 4 8.8.8.8          # connectivity test
curl -I https://example.com # fetch headers
curl -L https://...        # follow redirects
wget <url>                 # download (if installed)
ss -tulpn                  # listening ports/services
dig example.com             # DNS lookup (if installed)

ssh user@host                  # remote shell
ssh -i key.pem user@host       # with key
scp file user@host:/path/      # copy file to remote
rsync -avh dir/ user@host:/path/  # fast sync (great for backups)

uname -a                    # kernel/system info
hostnamectl                 # host details (systemd distros)
uptime                      # how long running + load
dmesg | less                # kernel messages
journalctl -xe              # system logs (systemd)
journalctl -u nginx --since "1 hour ago"

whoami                 # current user
id                     # user/group IDs
groups                 # groups you belong to
echo $PATH             # env var
export VAR=value       # set for current session
source ~/.bashrc       # reload shell config
“Every day” text tricks
wc -l file             # count lines
sort file | uniq -c    # count duplicates
cut -d',' -f1 file.csv # first CSV column
awk '{print $1}' file  # first whitespace-separated column
sed -n '1,20p' file    # print lines 1-20