chgroup Command

Purpose

Changes attributes for groups.

Syntax

chgroup [ -R load_module ] Attribute=Value ... Group

Description

Attention: Do not use the chgroup command if you have a Network Information Service (NIS) database installed on your system, as this could cause serious system database inconsistencies.

The chgroup command changes attributes for the group specified by the Group parameter. The group name must already exist. To change an attribute, specify the attribute name and the value you want to change it to in the Attribute=Value parameter.

To change the attributes for a group that was created with an alternate Identification and Authentication (I&A) mechanism, the -R flag can be used to specify the I&A loadable module. Load modules are defined in the /usr/lib/security/methods.cfg file.

You can use the Users application in Web-based System Manager (wsm) to change user characteristics. You could also use the System Management Interface Tool (SMIT) smit chgroup fast path to run this command.

Changing the ID for an account can compromise system security and as a result one should not do so. However, when the ID is changed using the chgroup command, ID collision checking is also controlled by the dist_uniqid attribute in the usw stanza of the /etc/security/login.cfg file. The behavior of ID collision control is the same as that described for the mkgroup command.

Restrictions on Changing Groups

To ensure the security of group information, there are restrictions on using the chgroup command. Only the root user or users with UserAdmin or aix.security.group.change authorization can use the chgroup command to change any group. These changes include:

Make a group an administrative group by setting the admin attribute to true.
Change any attributes of an administrative group.
Add users to an administrative group's administrators list.

An administrative group is a group with the admin attribute set to true. Members of the security group can change the attributes of nonadministrative groups including adding users to the list of administrators.

Flag

Item	Description
-R	Specifies the loadable I&A module used to change user's attributes.

Attributes

You change attributes by specifying an Attribute=Value parameter. If you have the proper authority you can set the following group attributes:

Item	Description
adms	Defines the users who can perform administrative tasks for the group, such as setting the members and administrators of the group. This attribute is ignored if admin = true, since only the root user can alter a group defined as administrative. The Value parameter is a list of comma-separated user login names. If you do not specify a Value parameter, all the administrators are removed.
admin	Defines the administrative status of the group. You can specify the following values: true Defines the group as administrative. Only the root user can change the attributes of groups defined as administrative. false Defines a standard group. The attributes of these groups can be changed by the root user or a member of the security group. This is the default value.
id	The group ID. The Value parameter is a unique integer string. Changing this attribute compromises system security and, for this reason, you should not change this attribute.
projects	Defines the list of projects to which the user's processes can be assigned. The value is a list of comma-separated project names and is evaluated from left to right. The project name should be a valid project name as defined in the system. If an invalid project name is found on the list, it will be reported as an error.
users	A list of one or more users in the form: User1,User2,...,Usern. Separate group member names with commas. Each user must be defined in the database configuration files. You cannot remove users from their primary group.
efs_initialks_mode	Specifies the initial mode of the group keystore. You can specify the following values: admin Root or other security privileged system users can open the group keystore using the admin key. guard Root users cannot open the group keystore using the admin key. The default value is admin. The attribute specifies the initial mode of the group keystore. You can use the attribute with the mkgroup command. After the keystore has been created, changing the attribute value with the chuser, chgroup, or chsec command, or manual editing does not change the mode of the keystore unless the keystore is deleted and a new one is created. To change the keystore mode, use the efskeymgr command. Restriction: The attribute is valid only when the system is EFS-enabled.
efs_keystore_algo	Specifies the algorithm that is used to generate the private key of the group during the keystore creation. You can specify the following values: RSA_1024 RSA_2048 RSA_4096 The default value is RSA_1024. You can use the attribute with the mkgroup command. After the keystore has been created, changing the value of this attribute with the chuser, chgroup, or chsec command, or manual editing does not regenerate the private key unless the keystore is deleted and a new one is created. To change the algorithm for the keys, use the efskeymgr command. Restriction: The attribute is valid only when the system is EFS-enabled.
efs_keystore_access	Specifies the database type of the group keystore. You can specify the following values: file Creates the */var/efs/groups/grpname/keystore* keystore file associated with the group. none The keystore is not created. All other keystore attributes have no effect. The default value is file. Restriction: The attribute is valid only when the system is EFS-enabled.

The adms and admin attributes are set in the /etc/security/group file. The remaining attributes are set in the /etc/group file. If any of the attributes you specify with the chgroup command are invalid, the command makes no changes at all.

Exit Status

This command returns the following exit values:

Item	Description
0	The command runs successfully and all requested changes are made.
>0	An error occurred. The printed error message gives further details about the type of failure.

Security

Access Control

This command should grant execute (x) access only to the root user and the security group. This command should be installed as a program in the trusted computing base (TCB). The command should be owned by the root user with the setuid (SUID) bit set.

Auditing Events

Event	Information
GROUP_Change	group, attributes

Files Accessed

Mode	File
rw	/etc/group
rw	/etc/security/group
r	/etc/passwd

Attention RBAC users and Trusted AIX® users: This command can perform privileged operations. Only privileged users can run privileged operations. For more information about authorizations and privileges, see Privileged Command Database in Security. For a list of privileges and the authorizations associated with this command, see the lssecattr command or the getcmdattr subcommand.

Limitations

Changing a group's attributes may not be supported by all loadable I&A modules. If the loadable I&A module does not support changing a group's attributes, an error is reported.

Examples

To add sam and carol to the finance group, which currently only has frank as a member, type:
```
chgroup users=sam,carol,frank  finance
```
To remove frank from the finance group, but retain sam and carol, and to remove the administrators of the finance group, type:
```
chgroup users=sam,carol adms= finance
```
In this example, two attribute values were changed. The name frank was omitted from the list of members, and the value for the adms attribute was left blank.
To change the LDAP I&A loadable module group user's attribute, type:
```
chgroup -R LDAP users=sam,frank monsters
```

Files

Item	Description
/usr/bin/chgroup	Specifies the path to the chgroup command.
/etc/group	Contains the basic attributes of groups.
/etc/security/group	Contains the extended attributes of groups.
/etc/passwd	Contains the basic attributes of users.