id 1 User Commands id display current user and group ID names id -a The id command displays the current real and effective user and group ID names or values. If the value does not have a corresponding entry in /etc/passwd or /etc/group, the value will be displayed without the corresponding name. The optional -a flag will display the group set on systems which support multiple concurrent group membership. /etc/group Group account information. /etc/passwd User account information. getgid2 , getgroups2 , getuid2