Useful Linux filesystem commands

pwd            # where am I
ls -lah        # long list, human sizes, include hidden files
cd -           # jump back to the previous directory

find . -name '*.log'          # by name
find . -type f -size +100M    # files larger than 100MB
grep -rn 'TODO' src/          # recursive search with line numbers

du -sh *          # size of each item in the current directory
du -sh * | sort -h# same, sorted smallest to largest
df -h             # free space per mounted filesystem

chmod +x script.sh   # make executable
chmod 644 file       # owner read/write, everyone else read
chown user:group file