Pourquoi "useradd" ne fonctionne-t-il pas pour ajouter un utilisateur au groupe principal?

Note: useradd est un utilitaire de bas niveau et il est fortement recommandé d'utiliser adduser (ou usermod) à la place sur les systèmes Ubuntu/Debian

• You are better off using the id -Gn username command to check primary/secondary membership rather than relying on /etc/group

• The -g option to useradd sets the primary (or login) group of a new user

  • If set to an existing group, this will not be reflected in /etc/group
  • But you can see the existing GID in /etc/passwd or using id -Gn username
  • Example (group izx is gid 1000): $ sudo useradd -g izx tom $ grep ^izx /etc/group izx:x:1000: $ grep ^tom /etc/passwd tom:x:1008:1000::/home/tom:/bin/sh $ id -Gn tom izx

• The -G option to useradd sets the secondary (or supplementary) group(s) of a new user

  • These memberships will be reflected in /etc/group and using id -Gn username
  • But not in /etc/passwd (compare to -g above)
  • Example (group izx is gid 1000): $ sudo useradd -G izx harry $ grep ^izx /etc/group izx:x:1000:harry $ grep ^harry /etc/passwd harry:x:1009:1009::/home/harry:/bin/sh $ id -Gn harry harry izx