linux-random.md

Linux Random

Memory usage:

$ free -h
$ ps -eo pmem,pcpu,vsize,pid,cmd | sort -k 1 -nr | head -5

Files by size:

$ du -hs /data/* | sort -h

What route will be used in route table to get to an address:

$ ip route get 10.85.131.138

Find and replace:

$ find ./ -type f -exec sed -i -e 's/apple/orange/g' {} \;

Find and replace with a backreference:

$ sed -E 's/\*([-A-ZÄÖÜÝŞŇÇŽa-zäöüýşňçž ]+)\*/\\emph{\1}/g'

Format json:

$ echo '{"foo": "lorem", "bar": "ipsum"}' | python -mjson.tool
$ echo '{"foo": "lorem", "bar": "ipsum"}' | jq

Check if host is reachable using netcat on given port:

$ nc -zv 192.0.0.5 22

Copy files to remote hosts:

$ scp -r sourcedir/ [email protected]:/dest/dir/

Sudo with current users environment variables:

$ sudo -E <command>

Systemctl

$ systemctl list-unit-files --state=enabled

View journal logs

$ journalctl -u nginx.service --since today

Loop through files to do something:

$ for f in *.jpg; do echo "$f"; done

Check which ports the server is listening on

$ netstat -antup

Execute as another user

$ sudo -u admin whoami

Tracing

$ tcptraceroute my-site.com 443
# equivalent to
$ traceroute -T -O info -p 443  my-site.com