Change a users primary group after login Post: 302106439

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Top Forums UNIX for Advanced & Expert Users Change a users primary group after login Post 302106439 by Perderabo on Thursday 8th of February 2007 12:53:22 PM

02-08-2007

Administrator Emeritus

Unix has been designed to render such an operation as unneeded. So why do you want to do this? A user can access files based on secondary groups. If you are concerned about controlling the gid of newly created files, you can do that by setting the sgid bit in the directory. I checked the man page for chmod on AIX 5.3 and I found this language:

Quote:

S_ISGID Enables the setgid attribute for an executable file. A process executing this program acquires the access rights of the group of the file. Also, enables the group-inheritance attribute for a directory. Files created in this directory have a group equal to the group of the directory.

In the old days, we would need to change the primary group because secondary groups had not been invented. The newgrp command still exists in many versions of unix, including AIX, and you can use it if you want. But don't be surprised if you don't like it very much.

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LEARN ABOUT BSD

newgrp

NEWGRP(1)							   User Commands							 NEWGRP(1)

NAME

       newgrp - log in to a new group

SYNOPSIS

       newgrp [-] [group]

DESCRIPTION

       The newgrp command is used to change the current group ID during a login session. If the optional - flag is given, the user's environment
       will be reinitialized as though the user had logged in, otherwise the current environment, including current working directory, remains
       unchanged.

       newgrp changes the current real group ID to the named group, or to the default group listed in /etc/passwd if no group name is given.
       newgrp also tries to add the group to the user groupset. If not root, the user will be prompted for a password if she does not have a
       password (in /etc/shadow if this user has an entry in the shadowed password file, or in /etc/passwd otherwise) and the group does, or if
       the user is not listed as a member and the group has a password. The user will be denied access if the group password is empty and the user
       is not listed as a member.

       If there is an entry for this group in /etc/gshadow, then the list of members and the password of this group will be taken from this file,
       otherwise, the entry in /etc/group is considered.

CONFIGURATION

       The following configuration variables in /etc/login.defs change the behavior of this tool:

       SYSLOG_SG_ENAB (boolean)
	   Enable "syslog" logging of sg activity.

FILES

       /etc/passwd
	   User account information.

       /etc/shadow
	   Secure user account information.

       /etc/group
	   Group account information.

       /etc/gshadow
	   Secure group account information.

SEE ALSO

       id(1), login(1), su(1), sg(1), gpasswd(1), group(5), gshadow(5).

shadow-utils 4.5						    01/25/2018								 NEWGRP(1)

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