Managing User Accounts and User Environments in Oracle® Solaris 11.2

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Updated: September 2014
 
 

User Account Components

This section describes the various components of a user account.

User (Login) Names

User names, also called login names, enable users to access their own systems and remote systems that have the appropriate access privileges. You must choose a user name for each user account that you create.

Consider establishing a standard way of assigning user names so that they are easier for you to track. Also, names should be easy for users to remember. A simple scheme when selecting a user name is to use the first name initial and first seven letters of the user's last name. For example, John Smith becomes jsmith. If this scheme results in duplicate names, you can use the first initial, middle initial, and the first six characters of the user's last name. For example, John Jay Smith becomes jjsmith.

    If this scheme still results in duplicate names, consider using the following scheme to create a user name:

  • Using the first initial, middle initial, and first five characters of the user's last name

  • Adding the number 1, or 2, or 3, and so on, until you have a unique name


Note -  User names must be distinct from any mail aliases that are known to the system or to a NIS domain. Otherwise, mail might be delivered to the alias rather than to the actual user.

For detailed guidelines on setting up user (login) names, see Guidelines for Assigning User Names, User IDs, and Group IDs.

User ID Numbers

A user identification number (UID) is associated with each user name. The UID number identifies the user name to any system on which the user attempts to log in. It also is used by systems to identify the owners of files and directories. If you create user accounts for a single individual on a number of different systems, always use the same user name and ID number. In that way, the user can easily move files between systems without ownership problems.

UID numbers must be a whole number that is less than or equal to 2147483647. UID numbers are required for both regular user accounts and special system accounts. The following table lists the UID numbers that are reserved for user accounts and system accounts.

Table 1-1  Reserved UID Numbers
UID Numbers
User or Login Accounts
Description
0 – 99
root, daemon, bin, sys, and so on
Reserved for use by the operating system
100 – 2147483647
Regular users
General purpose accounts
60001 and 65534
nobody and nobody4
NFS Anonymous users
60002
noaccess
Non-trusted users

Do not assign UIDs 0 through 99. These UIDs are reserved for allocation by Oracle Solaris. By definition, root always has UID 0, daemon has UID 1, and pseudo-user bin has UID 2. In addition, you should give uucp logins and pseudo user logins, such as who, tty, and ttytype, low UIDs so that they fall at the beginning of the passwd file.

For additional guidelines on setting up UIDs, see Guidelines for Assigning User Names, User IDs, and Group IDs.

As with user (login) names, you should adopt a scheme for assigning unique UID numbers. Some companies assign unique employee numbers. Then, administrators add a number to the employee number to create a unique UID number for each employee.

To minimize security risks, you should avoid reusing the UIDs from deleted accounts. If you must reuse a UID, remove the account information completely so that the new user is not affected by attributes set for a former user. For example, a former user might have been included in a printer deny list. However, denying access to that printer might be inappropriate for the new user.

Using Large User IDs and Group IDs

UIDs and group IDs (GIDs) can be assigned up to the maximum value of a signed integer, or 2147483647.

The following table describes UID and GID limitations.

Table 1-2  Large UID and GID Limitation Summary
UID or GID
Limitations
262144 or greater
Users who use the cpio command with the default archive format to copy a file see an error message for each file. The UIDs and GIDs are set to nobody in the archive.
2097152 or greater
Users who use the cpio command with the -H odc format or the pax -x cpio command to copy files see an error message returned for each file. The UIDs and GIDs are set to nobody in the archive.
1000000 or greater
Users who use the ar command have their UIDs and GIDs set to nobody in the archive.
2097152 or greater
Users who use the tar command, the cpio -H ustar command, or the pax -x tar command have their UIDs and GIDs set to nobody.

UNIX Groups

A group is a collection of users who can share files and other system resources. For example, users who working on the same project could be formed into a group. A group is traditionally known as a UNIX group.

Each group must have a name, a group identification (GID) number, and a list of user names that belong to the group. A GID number identifies the group internally to the system.

    The two types of groups that a user can belong to are as follows:

  • Primary group – Specifies a group that the operating system assigns to files that are created by the user. Each user must belong to a primary group.

  • Supplemental groups – Specifies one or more groups to which a user also belongs. Users can belong to up to 1024 supplemental groups.

For detailed guidelines on setting up group names, see Guidelines for Assigning User Names, User IDs, and Group IDs.

Sometimes, a user's secondary group is not important. For example, ownership of files reflect the primary group, not any secondary groups. Other applications, however, might rely on a user's secondary group memberships. For example, a user has to be a member of the sysadmin group (group 14) to use the Admintool software in previous Oracle Solaris releases. However, it does not matter if group 14 is the user's current primary group.

The groups command lists the groups that a user belongs to. A user can have only one primary group at a time. However, users can temporarily change their primary group to any other group in which the user is a member by using the newgrp command.

When adding a user account, you must assign a primary group for a user or accept the default group, staff (group 10). The primary group should already exist. If the primary group does not exist, specify the group by a GID number. User names are not added to primary groups because the list might become too long. Before you can assign users to a new secondary group, you must create the group and assign it a GID number.

Groups can be local to a system or managed through a name service. To simplify group administration, you should use a name service such as NIS or a directory service such as LDAP. These services enable you to centrally manage group memberships.

User Passwords

You can specify a password for a user when you add the user. Or, you can force the user to specify a password when the user first logs in to the system. Although user names are publicly known, passwords must be kept secret and known only to users. Each user account should be assigned a password.

    User passwords must comply with the following syntax:

  • Password length is defined by the value PASSLENGTH in the /etc/default/password file.

    The default password hashing algorithm is SHA256. As a result, user passwords are no longer limited to eight characters as in previous Oracle Solaris releases. The eight-character limitation applies only to passwords that use the older crypt_unix (5) algorithm, which has been preserved for backward compatibility with any existing passwd file entries and NIS maps.

    New passwords must match the complexity rules within the maximum number of characters that are allowed for the password algorithm. Thus, if you are using the crypt_unix algorithm and you type a 20-character password, the password must match the complexity rules within the first 8 characters. If the password algorithm is any of the other algorithms, the password must match the complexity rules within the full password that is entered, which is 20 in this example.

  • Each password must meet the configured complexity constraints that are specified in the /etc/default/passwd file.

  • Each password must not be a member of the configured dictionary as specified in the /etc/default/passwd file.

  • New passwords must not be contained in a name service's password history.

Password rules are explained in detail in the passwd (1) man page.

To make your computer systems more secure, users should change their passwords periodically. For a high level of security, you should require users to change their passwords every six weeks. Once every three months is adequate for lower levels of security. System administration logins (such as root and sys) should be changed monthly, or whenever a person who knows the root password leaves the company or is reassigned.

Many breaches of computer security involve guessing a legitimate user's password. You should make sure that users avoid using proper nouns, names, login names, and other passwords that a person might guess just by knowing something about the user.

    Good choices for passwords include the following:

  • Phrases (beammeup).

  • Nonsense words made up of the first letters of every word in a phrase. For example, swotrb for SomeWhere Over The RainBow.

  • Words with numbers or symbols substituted for letters. For example, sn00py for snoopy.

    Do not use these choices for passwords:

  • Your name (spelled forwards, backwards, or jumbled)

  • Names of family members or pets

  • Car license numbers

  • Telephone numbers

  • Social Security numbers

  • Employee numbers

  • Words related to a hobby or interest

  • Seasonal themes, such as Santa in December

  • Any word in the dictionary

Home Directories

The home directory is the portion of a file system that is allocated to a user for storing private files. The amount of space you allocate for a home directory depends on the size of the system on which the directory is hosted, the kinds of files the user creates, the file size, and the number of files that are created.

A home directory can be located either on the user's local system or on a remote file server. In either case, by convention the home directory should be created as /export/home/username. For a large site, you should store home directories on a server. Use a separate file system for each user for example, /export/home/alice or /export/home/bob. By creating separate file systems for each user, you can set properties or attributes based on each user's needs.

Regardless of where their home directory is located, users usually access their home directories through a mount point named /home/username. When AutoFS is used to mount home directories, you are not permitted to create any directories under the /home mount point on any system. The system recognizes the special status of /home when AutoFS is active. For more information about auto-mounting home directories, see Autofs Administration in Managing Network File Systems in Oracle Solaris 11.2 .

To use a home directory from anywhere on the network, you should always refer to the home directory as $HOME, not as /export/home/username. The latter is machine-specific. In addition, any symbolic links that are created in a user's home directory should use relative paths (for example, ../../../x/y/x) so that the links are valid no matter where the home directory is mounted.

For more information about how home directories are added when you create user accounts by using the command-line interface, see Guidelines for Setting Up User Accounts.

Naming Services

If you are managing user accounts for a large site, you might want to consider using a name or directory service such as LDAP or NIS. A name or directory service enables you to store user account information in a centralized manner instead of storing user account information in every system's /etc files. When you use a name service or a directory service for user accounts, users can move from system to system using the same user account without having their information duplicated on every system. Using a naming service or a directory service also ensures consistent user account information.

User's Work Environment

Besides having a home directory to create and store files, users need an environment that gives them access to the tools and resources they need to do their work. When a user logs in to a system, the user's work environment is determined by initialization files. These files are defined by the user's startup shell, which can vary depending on the release.

A good strategy for managing the user's work environment is to provide customized user initialization files, such as .bash_profile, .bash_login, .kshrc, or .profile, in the user's home directory.


Note -  Do not use system initialization files, such as /etc/profile or /etc/.login, to manage a user's work environment. These files reside locally on systems and are not centrally administered. For example, if AutoFS is used to mount the user's home directory from any system on the network, you would have to modify the system initialization files on each system to ensure a consistent environment whenever a user moved from system to system.

For detailed information about customizing user initialization files for users, see About the User's Work Environment.