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17. Sets effective, real, and saved user ID.
18. Changes directory to the user’s home directory.
19. Executes shell.
5.11.3.4 mingetty
mingetty, the minimal Linux getty, is invoked from /sbin/init when the system transitions from
single-user mode to multi-user mode. mingetty opens a pseudo tty port, prompts for a login name, and
invokes /bin/login to authenticate. Refer to the mingetty man page for more detailed information.
mingetty follows these steps:
1. Sets language.
2. Parses command-line setup options such as timeout and the alternate login program.
3. Updates the utmp file with pseudo tty information.
4. Prompts for login name.
5. Execs the login program.
The steps that are relevant to the identification and authorization subsystem are step 4, which prompts for the
user’s login name, and step 5, which executes the login program. The administrator can also use a
command-line option to terminate the program if a user name is not entered within a specific amount of time.
5.11.3.5 newgrp
The newgrp command changes the group ID using the group password for authentication. If run with a
command, it runs the command as a child shell and control returns to the parent, whose GID remains
unaltered. If run without a command argument, it execs an interactive shell. If no group is specified, the GID
from /etc/passwd is used. For more information on newgrp, see the newgrp(8) man page.
newgrp typically follows these processing steps:
1. Opens audit.
2. Sets its locale and message catalog information.
3. Gets its own name.
4. Opens its log file.
5. Gets its own gid.
6. Initializes environment variable handling.
7. Gets its own passwd entry.
8. Exits if there is no passwd entry.
9. Processes the command line.
10. Gets the group name of the group.
11. Checks all group with same GID for user membership.
12. Gets the shadow group name.
13. Check to see if the user needs to authenticate to take on the new GID.
14. Prompts for a password of authentication is necessary.
15. Logs the result.
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