# vi /etc/aliases
APPEND 
name1 alias1
name2 alias2

# postalias /etc/aliases

# grep ^alias main.cf
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases

# service postfix reload
or
# service postfix restart

# postconf -n

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
canonical_maps = hash:/etc/postfix/sender_canonical
command_directory = /usr/sbin