Which difference between /etc/aliases and virtual_alias_maps in Postfix and where should I put aliases from local accounts to virtual user accounts (i.e. from root to firstname.lastname@example.org)?
/etc/aliases is for compatibility with sendmail and is processed only by postfix/local delivery agent. Local LDA is used for domains on mydestination. The query is only for user local part (e.g. johndoe) as the awnser.
virtual_alias_maps is always processed and the query is by full email (e.g. email@example.com) as the awnser.