# Change a file's owner:
chown <user> <file>

# Change a file's owner and group:
chown <user>:<group> <file>

# Set user to match group value
chown <user>: <file>

# Set group to match user value
chown :<group> <file>

# Change a directory's owner recursively:
chown -R <user> <directory>

# Change ownership to match another file:
chown --reference=<reference-file> <file>
