fedora16 note---user&group

1、configure umask in /etc/bashrc

2、when the home directory is created, default configuration files are copied into it from the /etc/skel/ directory.

3、useradd [options]  username

Option	Description
-c 'comment'	comment can be replaced with any string. This option is generally used to specify the full name of a user.
-d home_directory	Home directory to be used instead of default /home/username/.
-e date	Date for the account to be disabled in the format YYYY-MM-DD.
-f days	Number of days after the password expires until the account is disabled. If 0 is specified, the account is disabled immediately after the password expires. If -1 is specified, the account is not be disabled after the password expires.
-g group_name	Group name or group number for the user's default group. The group must exist prior to being specified here.
-G group_list	List of additional (other than default) group names or group numbers, separated by commas, of which the user is a member. The groups must exist prior to being specified here.
-m	Create the home directory if it does not exist.
-M	Do not create the home directory.
-N	Do not create a user private group for the user.
-p password	The password encrypted with crypt.
-r	Create a system account with a UID less than 1000 and without a home directory.
-s	User's login shell, which defaults to /bin/bash.
-u uid	User ID for the user, which must be unique and greater than 999.

4、groupadd[options]group_name

Option	Description
-f, --force	When used with -g gid and gid already exists, groupadd will choose another unique gid for the group.
-g gid	Group ID for the group, which must be unique and greater than 999.
-K, --key key=value	Override /etc/login.defs defaults.
-o, --non-unique	Allow to create groups with duplicate.
-p, --password password	Use this encrypted password for the new group.
-r	Create a system group with a GID less than 1000.

5、chage [options] username

	Description
-d  days	Specifies the number of days since January 1, 1970 the password was changed.
-E date	Specifies the date on which the account is locked, in the format YYYY-MM-DD. Instead of the date, the number of  days since January 1, 1970 can also be used.
-I days	Specifies the number of inactive days after the password expiration before locking the account. If the value is 0, the account is not locked after the password expires.
-l	Lists current account aging settings.
-m days	Specify the minimum number of days after which the user must change passwords. If the value is 0, the password does not expire.
-M days	Specify the maximum number of days for which the password is valid. When the number of days specified by this option plus the number of days specified with the-d option is less than the current day, the user must change passwords before using the account.
-W days	Specifies the number of days before the password expiration date to warn the user.

6、To assign a null password instead, use the following command:   passwd -d  username
7、commands

• chage(1) — A command to modify password aging policies and account expiration.
• gpasswd(1) — A command to administer the /etc/group file.
• groupadd(8) — A command to add groups.
• grpck(8) — A command to verify the /etc/group file.
• groupdel(8) — A command to remove groups.
• groupmod(8) — A command to modify group membership.
• pwck(8) — A command to verify the /etc/passwd and /etc/shadow files.
• pwconv(8) — A tool to convert standard passwords to shadow passwords.
• pwunconv(8) — A tool to convert shadow passwords to standard passwords.
• useradd(8) — A command to add users.
• userdel(8) — A command to remove users.
• usermod(8) — A command to modify users.