Users on Linux

Add user

adduser - interactive user adding
useradd - also adding users, but with parameters (not-interactively)

Change password

passwd
passwd other_username

Remove user

userdel # removes user account, but keeps its home folder
userdel -r # removes user account and its home folder

Users and groups

Add a existing user to the existing group:

usermod -a -G my-group my-username

Other examples

List groups that the user is a member of:

groups user_name

Actualize user/group membership database:

# logout + login
# OR
newgrp group_name # logs the user to the group

Group for new files

There are a couple ways to do this (source):

1. You can change the default group for all files created in a particular directory by setting the setgid flag on the directory ( chmod g+s _dir_ ). New files in the directory will then be created with the group of the directory (set using chgrp <group> <dir> ). This applies to any program that creates files in the directory.

   Note that this is automagically inherited for new subdirectories (as of Linux 3.10), however, if sub-directories were already present, this change won't be applied to them (use the -R flag for that).

2. If the setgid flag is not set, then the default group will be set to the current group id of the creating process. Although this can be set using the newgrp command, that creates a new shell that is difficult to use within a shell script. If you want to execute a particular command (or set of commands) with the changed group, use the command sg <group> <command> .

   sg is not a POSIX standard command but is available on Linux.