Linux/Bash 치트시트

ls -la /var/log
ls -lah --sort=size   # sort by size, human-readable

cd /var/log          # absolute path
cd ../config         # relative path
cd ~                 # home directory
cd -                 # previous directory

mkdir -p /opt/app/{config,logs,data}
mkdir -p src/{components,utils,hooks}

cp file.txt backup.txt
cp -r src/ src_backup/
cp -a /var/www/ /backup/www/   # preserve permissions & timestamps

mv old_name.txt new_name.txt      # rename
mv *.log /var/log/archive/        # move multiple files
mv -i file.txt /dest/             # prompt before overwrite

rm file.txt
rm -rf /tmp/build_*
rm -i important.txt   # interactive (confirm before delete)

find /var/log -name "*.log" -mtime -7
find . -type f -size +100M
find . -name "*.tmp" -delete
find . -type f -name "*.js" ! -path "*/node_modules/*"

ln -s /opt/app/current /opt/app/v2.1.0
ln -sf /etc/nginx/sites-available/mysite /etc/nginx/sites-enabled/

cat /etc/hostname
cat -n script.sh          # with line numbers
cat file1.txt file2.txt > merged.txt

head -20 access.log       # first 20 lines
tail -50 error.log        # last 50 lines
tail -f /var/log/syslog   # follow in real-time

grep -r "ERROR" /var/log/
grep -rn "TODO" src/          # with line numbers
grep -ri "password" . --include="*.env"
grep -v "^#" config.ini       # exclude comment lines

wc -l access.log              # line count
find . -name "*.py" | wc -l   # count Python files
cat README.md | wc -w         # word count

sort access.log | uniq -c | sort -rn | head -20
cut -d":" -f1 /etc/passwd | sort

less /var/log/syslog
# /pattern   search forward
# ?pattern   search backward
# n/N        next/prev match
# q          quit

cut -d":" -f1,3 /etc/passwd        # fields 1 and 3
cut -d"," -f2-4 data.csv           # fields 2 to 4
echo "hello world" | cut -c1-5     # first 5 characters

awk '{print $1, $4}' access.log         # print columns 1 and 4
awk -F":" '{print $1}' /etc/passwd     # custom delimiter
df -h | awk '$5 > 80 {print $6, $5}'  # disks over 80%

chmod 755 deploy.sh           # rwxr-xr-x
chmod 644 config.yml          # rw-r--r--
chmod +x script.sh            # add execute
chmod -R 750 /opt/app/        # recursive

chown www-data:www-data /var/www/html/
chown -R deploy:deploy /opt/app/
chown root:docker /var/run/docker.sock

umask              # show current mask
umask 022          # new files: 644, dirs: 755
umask 077          # new files: 600, dirs: 700 (strict)

sudo apt update
sudo -u postgres psql          # run as another user
sudo !!                        # re-run last command as root
su - deploy                    # switch to user with login shell

chgrp developers /shared/project/
chgrp -R www-data /var/www/

ps aux | grep nginx
ps aux --sort=-%mem | head -10     # top 10 by memory
ps -eo pid,ppid,%cpu,%mem,cmd --sort=-%cpu | head

top -o %MEM                   # sort by memory
htop                          # interactive (install: apt install htop)
top -bn1 | head -20           # batch mode, non-interactive

kill 12345                    # graceful SIGTERM
kill -9 12345                 # force SIGKILL
pkill -f "node server.js"     # kill by command pattern
killall nginx                 # kill all by name

nohup python train.py > output.log 2>&1 &
nohup ./long_task.sh &
disown %1                     # detach job from terminal

# Ctrl+Z to suspend current process
jobs                          # list jobs
bg %1                         # resume job 1 in background
fg %1                         # bring job 1 to foreground

systemctl status nginx
systemctl restart nginx
systemctl enable --now docker  # enable + start
journalctl -u nginx -f         # follow service logs

curl -s https://api.example.com/status | jq .
curl -X POST -H "Content-Type: application/json" \
  -d '{"key":"value"}' https://api.example.com/data
curl -o file.zip https://example.com/file.zip
curl -I https://example.com    # headers only

ssh user@192.168.1.100
ssh -i ~/.ssh/key.pem ec2-user@host
scp file.txt user@host:/tmp/
scp -r user@host:/var/log/ ./logs/

ss -tlnp                      # TCP listening ports
ss -tunap | grep :3000        # who is using port 3000
netstat -tlnp                 # (legacy) listening ports

ping -c 4 google.com
dig example.com A             # A record
dig +short example.com        # short output
nslookup example.com

wget https://example.com/file.tar.gz
wget -q -O - https://get.docker.com | sh
wget -r -np https://example.com/docs/

ip addr show
ip route show                 # routing table
ip -4 addr show eth0          # IPv4 only
hostname -I                   # all IP addresses

df -h
df -h /                       # root partition only
df -hT                        # include filesystem type

du -sh /var/log/*
du -sh * | sort -rh | head -10    # largest items
du -sh --max-depth=1 /home/

free -h
watch -n 2 free -h            # monitor every 2 seconds

uname -a                      # kernel version
uptime                        # how long running
lsb_release -a                # distro info
cat /etc/os-release           # OS details

lsblk                         # list block devices
lsblk -f                      # with filesystem info
mount | grep /dev/sd
sudo mount /dev/sdb1 /mnt/usb

dmesg | tail -20
journalctl -xe                # recent errors
journalctl --since "1 hour ago"
journalctl -u docker -f       # follow docker logs

sed 's/old/new/g' file.txt             # replace all
sed -i 's/localhost/0.0.0.0/g' config  # in-place edit
sed -n '10,20p' file.txt              # print lines 10-20
sed '/^#/d' config.ini                # delete comment lines

# Sum a column
awk '{sum+=$1} END {print sum}' numbers.txt
# Print lines where field > threshold
awk -F"," '$3 > 1000 {print $1, $3}' sales.csv
# Count occurrences
awk '{count[$1]++} END {for(k in count) print k, count[k]}' log.txt

echo "Hello World" | tr '[:upper:]' '[:lower:]'
echo "hello:world" | tr ':' '\n'
cat file.txt | tr -d '\r'      # remove carriage returns
cat file.txt | tr -s ' '       # squeeze repeated spaces

find . -name "*.log" | xargs rm
cat urls.txt | xargs -n1 curl -sO
find . -name "*.py" | xargs grep "import os"
echo "a b c" | xargs -n1 echo   # one per line

echo "deploy started" | tee deploy.log
command 2>&1 | tee -a output.log   # append mode

diff -u old.conf new.conf > changes.patch
patch < changes.patch
diff -rq dir1/ dir2/           # compare directories

tar -czf backup.tar.gz /opt/app/
tar -czf logs-$(date +%Y%m%d).tar.gz /var/log/*.log
tar -cjf archive.tar.bz2 src/     # bzip2 (higher compression)

tar -xzf backup.tar.gz
tar -xzf backup.tar.gz -C /opt/restore/
tar -tzf backup.tar.gz             # list contents only

zip -r project.zip src/ docs/
zip -e secure.zip secret.txt       # encrypted
unzip project.zip -d /opt/project/

gzip access.log                    # creates access.log.gz
gunzip access.log.gz               # decompress
zcat access.log.gz | grep "ERROR"  # read without extracting

rsync -avz src/ dest/
rsync -avz --delete /opt/app/ user@host:/opt/app/
rsync -avz --exclude="node_modules" . remote:/project/