Disk space

Use df / disk-free to check for free disk space:

df -h

Check file permissions

ls -ld <directory>

Create directories and forcing parents to be created

mkdir -p /parent/child

System info

Use neofetch.

sudo apt install neofetch
neofetch

Generate random keys

openssl rand -base64 36

Check docker logs

docker logs <container-name> # Basic
docker logs -f <container-name> # Paginate through
docker logs --tail 100 <container-name> # Limit lines
docker logs <container-name> | grep password