Ops Command Cheatsheet

• 2019/04/06

Linux

• Check for zombie processes

ps aux | grep [\<]defunct\>

• Show parents/children

ps auxf

• Kill a process

sudo kill -9 {PID}

• Disk usage

du -sh /path/to/dir

• Free space

df -h /path/to/dir

• CPU usage

top

• Memory usage

free -m

• List files sorted by mtime

ls -lrt

• List users

sudo cat /etc/passwd

• Switch user

sudo su - username

• SSH bastion config

cat ~/.ssh/config

• CPU details

sudo less /proc/cpuinfo

Shell

• Capture ls output into an array and loop:

items=(`ls -l`)
for item in ${items[@]}
do
  # work
 done

• Discard stdout:

./script.sh > /dev/null

• Append stdout to a file:

./script.sh >> filename.log

Apache

• Service status

sudo service httpd status

• Test config (vhosts, etc.)

sudo service httpd configtest

• Graceful restart

sudo service httpd graceful

DNS

• Query records

dig domain.com

• Lookup domain info

nslookup domain.com

• Check ownership

whois domain.com

MySQL

• Service status / restart

sudo service mysqld status
sudo service mysqld restart

• Log in

mysql -u USER -h HOST -p

• Show databases / tables

SHOW DATABASES;
SHOW TABLES;

• Show global variables

SHOW GLOBAL VARIABLES;
SHOW GLOBAL VARIABLES LIKE 'pattern';

• List users / grants

SELECT Host, User FROM mysql.user;
SHOW GRANTS FOR 'user';

Cron

• Service status

sudo service crond status

• View jobs

crontab -l