Estou tentando decifrar algum código de terminal [duplicado]

Question

O que significa -a e -G ? Obrigado.

sudo usermod -a -G www-data username

    

Answer 1

De man usermod :

   -a, --append
       Add the user to the supplementary group(s). Use only with the -G option.

   -G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
       A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no
       intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option.

       If the user is currently a member of a group which is not listed, the user will be removed from the group. This behaviour can be
       changed via the -a option, which appends the user to the current supplementary group list.

Em suma, sudo usermod -aG www-data username adiciona o usuário username ao grupo www-data .