Linux & server commands

pwd

cd /var/log && cd ~

ls -lah --sort=size

tree -L 2 -d /etc

mkdir -p projects/app/{src,test}

cp -a backup/. /restore/

mv old.txt archive/new.txt

rm -rf build_tmp/

touch app.log && ls -l app.log

less +F /var/log/syslog

tail -n 100 -f /var/log/nginx/access.log

wc -l *.csv

history | grep docker
!42

which python3; type -a ls

alias ll='ls -alh'

diff -u old.conf new.conf
cmp -s bin1 bin2

paste a.txt b.txt
join -t: file1 file2

cat -n src/app.tsx
cat -b ~/.bashrc | head -40

nl -ba nginx.conf | less
nl -v10 -i10 log.txt   # start at 10, step 10

less -N /etc/ssh/sshd_config
less -NS long.csv   # -S = chop long lines horizontally

bat package.json
bat -n main.go
bat --theme=GitHub --wrap=never README.md

vim +"set number" config.yml
:set nu
:set relativenumber
:42   # jump to line 42
:set nowrap

fold -w 80 wide.txt
fmt -w 72 memo.txt

grep -n "function " src/*.ts
grep -nR "TODO" . --include='*.go'

grep -Rni 'ERROR' /var/log/myapp
grep -E '50[0-9]|timeout' access.log
grep -v '^#' /etc/nginx/nginx.conf

grep -E '(Failed|Invalid)' auth.log

grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' log.txt

rg 'TODO|FIXME' src/
rg -l 'import react' --type ts
rg -n --hidden 'password'

sed -i.bak 's/api\.old/api.new/g' *.yaml
sed -n '100,200p' huge.log
sed '/^$/d' file.txt  # drop blank lines

awk '{print $1,$NF}' access.log
awk -F: '$3>=1000 {print $1}' /etc/passwd
awk '{sum+=$1} END {print sum}' nums.txt

find . -name '*.log' -mtime +7 | xargs gzip
kubectl get pods -o name | xargs -I{} kubectl logs {} --tail=5
xargs -a urls.txt -P4 curl -s -o /dev/null -w '%{url_effective}\n'

cut -d' ' -f1,7 access.log
cut -c1-80 wide.txt

cat file | tr '[:upper:]' '[:lower:]'
tr -d '\r' < win.txt > unix.txt

sort -t: -k3 -n /etc/passwd
sort ips.txt | uniq -c | sort -rn

kubectl apply -f app.yaml 2>&1 | tee apply.log
./deploy.sh | tee >(grep -i error >&2)

chmod 644 file.txt
chmod u+x script.sh

sudo chown -R www-data:www-data /var/www

umask 027

sudo -u postgres psql
sudo visudo

su - deploy
sudo su -

id
groups $USER

passwd
sudo passwd alice

getfacl /shared
setfacl -m u:bob:rwx /shared

ps aux | grep nginx
ps -ef --forest

htop -u $USER

pgrep -af node
pidof sshd

kill -15 $PID
kill -9 $PID  # last resort

sleep 100 &
jobs
fg %1

nohup ./long_job.sh >out.log 2>&1 &

nice -n 10 heavy_cmd
sudo renice -n -5 -p $PID

timeout 30s curl -v slow.api/health

watch -n2 'df -h /'

systemctl status nginx
systemctl is-active docker

systemctl list-units --failed
systemctl list-units --type=service --state=running
systemctl list-timers

crontab -l
crontab -e
sudo crontab -l -u www-data

curl -I https://example.com
curl -d '{}' -H 'Content-Type: application/json' URL

wget -O file.zip https://cdn/file.zip

ssh user@host
scp file user@host:/tmp/

ping -c 4 1.1.1.1

traceroute example.com

dig +short A api.example.com
host -t MX example.com

ss -tlnp
ss -tan sport = :443

netstat -tulpn 2>/dev/null | grep LISTEN

nc -vz db.internal 5432
cat foo | nc host 1234

sudo iptables -L -n -v
sudo nft list ruleset

ip addr show
ip route
ip link set eth0 up

mtr -rwzbc 100 example.com

openssl s_client -connect api.example.com:443 -servername api.example.com </dev/null
openssl s_client -showcerts -connect host:443 2>/dev/null | openssl x509 -noout -dates

whois example.com
whois 203.0.113.9

resolvectl status
resolvectl query api.example.com

df -h
 df -h /var

du -sh *
sudo du -xh /var | sort -rh | head

lsblk -f
sudo blkid

mount | column -t
sudo mount /dev/sdb1 /mnt

free -h
watch -n1 free -h

grep -E 'Mem|Swap' /proc/meminfo

sync && sudo umount /usb

find /var/log -type f -size +100M
find . -mtime +30

ncdu /
ncdu -x /var

sudo iotop -oPa  # only active, accum, all processes

journalctl -u nginx -f --since '1 hour ago'
journalctl -b -p err

dmesg -T | tail -50
dmesg | grep -i oom

strace -p $PID -f -e trace=network

sudo lsof -iTCP:443 -sTCP:LISTEN
sudo lsof -i :8080
sudo lsof -p $PID
sudo lsof +D /var/log 2>/dev/null | head

sudo fuser -v 443/tcp
sudo fuser -km /mnt/stale   # kill holders — careful

sudo perf top -p $PID
sudo perf record -g -p $PID sleep 15 && sudo perf report

sudo gdb -p $PID -batch -ex 'thread apply all bt' -ex q

sudo tcpdump -i any port 443 -nn -c 20

iostat -xz 1
vmstat 1 5

ss -s

uptime
w

last -10
sudo lastb | head

docker ps -a
docker ps -s

docker images
docker image prune -a

docker build -t myapp:1 .
docker push registry/myapp:1

docker run -d -p 8080:80 --name web nginx
docker run -it --rm alpine sh

docker exec -it web bash

docker logs -f --tail 100 web

docker inspect -f '{{.NetworkSettings.IPAddress}}' web

docker stats --no-stream

docker compose up -d
docker compose logs -f api

docker network ls
docker volume prune

docker system df
docker system prune -a

kubectl get pods -A
kubectl get nodes -o wide

kubectl describe pod mypod -n prod

kubectl logs deploy/api -f --tail=200
kubectl logs pod/x -p

kubectl exec -it mypod -n prod -- /bin/sh

kubectl apply -f manifest.yaml
kubectl apply -k overlays/dev

kubectl delete pod stuck-pod --force --grace-period=0

kubectl port-forward svc/grafana 3000:3000

kubectl rollout status deploy/api
kubectl rollout undo deploy/api

kubectl config use-context staging
kubectl config get-contexts

kubectl top pods
kubectl top nodes

kubectl get events -n prod --sort-by=.lastTimestamp

helm list -A
helm upgrade --install mychart ./chart -n prod
helm rollback myrelease 1 -n prod

sudo apt update && sudo apt upgrade -y
sudo apt install -y nginx curl
apt-cache search postgres

dpkg -l | grep nginx
dpkg -L nginx
sudo apt-file search bin/jpegtran

sudo dnf install -y git
sudo dnf upgrade --refresh
sudo yum repolist all

rpm -qa | grep kernel
rpm -ql nginx
rpm -qi bash
rpm -qf /usr/bin/python3

snap list
sudo snap install kubectl --classic
flatpak remote-ls | head

tar czf backup.tgz /etc/nginx
tar xzf release.tar.gz
tar tvf backup.tar | head

gzip -k big.log
zcat access.log.gz | head

zip -r dist.zip build/
unzip -l archive.zip

rsync -avz ./site/ user@host:/var/www/
rsync -av --delete src/ backup/src/
rsync -e ssh -avz data/ backup-host:/data/

git clone https://github.com/org/repo.git
git status
git log -3 --oneline
git diff --stat origin/main

env | sort
printenv PATH
export MY_VAR=test

ssh-keygen -t ed25519 -C 'you@company.com'
eval $(ssh-agent) && ssh-add ~/.ssh/id_ed25519

aws sts get-caller-identity
aws configure list
aws ec2 describe-instances --filters Name=tag:Env,Values=prod --query ...
aws logs tail /ecs/my-service --since 10m --follow

terraform fmt -recursive
terraform init
terraform plan -out=tfplan
terraform apply tfplan

kubectl get pods -o json | jq '.items[].metadata.name'
aws ec2 describe-instances | jq '.Reservations[].Instances[].InstanceId'