This chapter provides guidelines and planning information for managing user accounts and groups. It also provides overview information about setting up user accounts and groups in a network environment. This chapter includes information about the files used to store user account and group information and about customizing the user's work environment.
This is a list of the concept information in this chapter.
For step-by-step instructions on managing user accounts and groups, see Chapter 3, Setting Up and Maintaining User Accounts and Groups (Tasks).
In this Solaris release, role-based access control (RBAC) provides a flexible way to package superuser privileges for assignment to user accounts so that you don't have to give all superuser privileges to a user that needs to solve a specific problem.
See "Role-Based Access Control" in System Administration Guide, Volume 2 for more information.
One of the basic system administration tasks is to set up a user account for each user at a site. A typical user account includes the information a user needs to log in and use a system (without having the system's root password). User account information consists of four main components:
Also, when you set up a user account, you can add the user to predefined groups of users. A typical use of groups is to set up file and directory access only to users who are part of a group (using the group permissions on a file or directory).
For example, you might have a directory containing top secret files that only a few users should be able to access. You could set up a group called topsecret that include the users working on the top secret project, and you could set up the top secret files with read permission for the topsecret group. That way, only the users in the topsecret group would be able to read the files.
There is also a special type of user account called a role, which is used to give selected users special privileges. See "Role-Based Access Control" in System Administration Guide, Volume 2 for more information.
The following sections describe some guidelines and planning information for creating user accounts.
If you are managing user accounts for a large site, you might want to consider using a name service such as NIS or NIS+. A name 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 using a name service for user accounts, users can move from system to system using the same user account without having site-wide user account information duplicated in every system's /etc files. Using a name service also promotes centralized and consistent user account information.
User names, also called login names, let users access their own systems and remote systems that have the appropriate access privileges. You must choose a user name for each user account you create. User names must:
Be unique within your organization, which might span multiple domains
Contain from two to eight letters and numerals (the first character must be a letter and at least one character must be a lowercase letter)
It is helpful to establish a standard way of forming user names, and the 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, Ziggy Ignatz becomes zignatz. If that 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, Ziggy Top Ignatz becomes ztignatz. If that still results in duplicate names, you can use the first initial, middle initial, first five characters of the user's last name, and the number 1, or 2, or 3, and so on, until you have a unique name.
Each new user name must be distinct from any mail aliases known to the system or to an NIS or NIS+ domain. Otherwise, mail might be delivered to the alias rather than to the actual user.
Associated with each user name is a user identification (UID) number. The UID number identifies the user name to any system on which the user attempts to log in, and it 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 user ID. In that way, the user can easily move files between systems without ownership problems.
UID numbers must be a whole number less than or equal to 2147483647, and they are required for both regular user accounts and special system accounts. The table below lists the UID numbers reserved for user accounts and system accounts.
Table 2-1 Reserved UID Numbers
User ID Numbers |
Login Accounts |
Reserved For ... |
---|---|---|
0 - 99 |
root, daemon, bin, sys, etc. |
System accounts |
100 - 2147483647 |
Regular users |
General purpose accounts |
60001 |
nobody |
Unauthenticated users |
60002 |
noaccess |
Compatibility with Solaris 2.0 and compatible versions and SVR4 releases |
Although UID numbers 0 through 99 are reserved, you can add a user with one of these numbers. However, do not use them for regular user accounts. 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, like who, tty, and ttytype, low UIDs so they fall at the beginning of the passwd file.
As with user (login) names, you should adopt a scheme to assign unique UIDs. Some companies assign unique employee numbers, and administrators add 1000 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, "wipe the slate clean" so the new user is not affected by attributes set for a former user. For example, a former user might have been denied access to a printer--by being included in a printer deny list--but that attribute might not be appropriate for the new user. If need be, you can use duplicate UIDs in an NIS+ domain if the supply of unique UIDs is exhausted.
Previous Solaris software releases used 32-bit data types to contain the user IDs (UIDs) and group IDs (GIDs), but UIDs and GIDs were constrained to a maximum useful value of 60000. Starting with the Solaris 2.5.1 release and compatible versions, the limit on UID and GID values has been raised to the maximum value of a signed integer, or 2147483647.
UIDs and GIDs over 60000 do not have full functionality and are incompatible with many Solaris features, so avoid using UIDs or GIDs over 60000.
The table below describes interoperability issues with previous Solaris and Solaris product releases.
Table 2-2 Interoperability Issues for UIDs/GIDs Over 60000
Category |
Product/Command |
Issues/Cautions |
---|---|---|
NFSTM Interoperability |
SunOSTM 4.0 NFS software and compatible versions |
NFS server and client code truncates large UIDs and GIDs to 16 bits. This can create security problems if SunOS 4.0 and compatible machines are used in an environment where large UIDs and GIDs are being used. SunOS 4.0 and compatible systems require a patch. |
Name Service Interoperability |
NIS name service File-based name service |
Users with UIDs above 60000 can log in or use the su command on systems running the Solaris 2.5 and compatible versions, but their UIDs and GIDs will be set to 60001 (nobody). |
|
NIS+ name service |
Users with UIDs above 60000 are denied access on systems running Solaris 2.5 and compatible versions and the NIS+ name service. |
Printed UIDs/GIDs |
OpenWindows File Manager |
Large UIDs and GIDs do not display correctly if the OpenWindowsTM File Manager is used with the extended file listing display option. |
Table 2-3 Large UID/GID Limitation Summary
Although user names are publicly known, passwords must be kept secret and known only to users. Each user account should be assigned a password, which is a combination of six to eight letters, numbers, or special characters. You can set a user's password when you create the user account and have the user change it when logging in to a system for the first time.
To make your computer systems more secure, ask users to 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:
Phrases (beammeup)
Nonsense words made up of the first letters of every word in a phrase (swotrb for SomeWhere Over The RainBow)
Words with numbers or symbols substituted for letters (sn00py for snoopy)
Do not use these choices for passwords:
Your name, forwards, backwards, or jumbled
Names of family members or pets
Car license numbers
Telephone numbers
Social Security numbers
Employee numbers
Names related to a hobby or interest
Seasonal themes, such as Santa in December
Any word in the dictionary
If you are using NIS+ or the /etc files to store user account information, you can set up password aging on a user's password. Password aging enables you to force users to change their passwords periodically or to prevent a user from changing a password before a specified interval. If you want to prevent an intruder from gaining undetected access to the system by using an old and inactive account, you can also set a password expiration date when the account become disabled.
The home directory is the portion of a file system allocated to a user for storing private files. The amount of space you allocate for a home directory depends on the kinds of files the user creates and the type of work done. As a general rule, you should allocate at least 15 Mbytes of disk space for each user's home directory.
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 /export/homen directory to facilitate backing up and restoring home directories (for example, /export/home1, /export/home2).
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 automounting home directories, see System Administration Guide, Volume 3.
To use the home directory anywhere on the network, you should always refer to it as $HOME, not as /export/home/username. The latter is machine-specific. In addition, any symbolic links created in a user's home directory should use relative paths (for example, ../../../x/y/x), so the links will be valid no matter where the home directory is mounted.
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 that are defined by the user's startup shell, such as the C, Korn, or Bourne shell.
A good strategy for managing the user's work environment is to provide customized user initialization files (.login, .cshrc, .profile) in the user's home directory. See "Customizing a User's Work Environment" for detailed information about customizing user initialization files for users. After you create the customized user initialization files, you can add them to a user's home directory when you create a new user account.
A recommended one-time task is to set up separate directories, called skeleton directories, on a server (you can use the same server where the user's home directories are stored). The skeleton directories enable you to store customized user initialization files for different types of users.
Do not use system initialization files (/etc/profile, /etc/.login) to manage a user's work environment, because they 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, then you would have to modify the system initialization files on each system to ensure a consistent environment when a user moved from system to system.
Another way to customize user accounts is through role-based access control. See "Role-Based Access Control" in System Administration Guide, Volume 2 for more information.
A group is a collection of users who can share files and other system resources. For example, the set of users 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 identifies the group internally to the system. The two types of groups that a user can belong to are:
Primary group - Specifies a group that the operating system assigns to files created by the user. Each user must belong to a primary group.
Secondary groups - Specifies one or more groups to which a user also belongs. Users can belong to up to 16 secondary groups.
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 memberships. For example, a user has to be a member of the sysadmin group (group 14) to use the Admintool software, but it doesn't matter if group 14 is his or her 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, the user can temporarily change the user's primary group (with the newgrp command) to any other group in which the user is a member.
When adding a user account, you must assign a primary group for a user or accept the default: staff (group 10). The primary group should already exist (if it doesn't exist, specify the group by a GID number). User names are not added to primary groups. If they were, 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 can be managed through a name service. To simplify group administration, you should use a name service like NIS+, which enables you to centrally manage group memberships.
The table below lists the recommended tools for managing users and groups.
Table 2-4 Recommended Tools for Managing Users and Groups
If You Are Managing Users and Groups ... |
The Recommended Tool Is ... |
And You Will Need ... |
To Start This Tool See ... |
---|---|---|---|
On remote and/or local systems in a networked, name service (NIS, NIS+) environment |
AdminSuiteTM 2.3's User and Group Manager (graphical user interface) |
Graphics monitor running an X window environment such as CDE | |
On a local system |
Admintool (graphical user interface) |
Graphics monitor running an X window system such as CDE |
Chapter 3, Setting Up and Maintaining User Accounts and Groups (Tasks) |
The Solaris commands useradd and groupadd also let you set up users and groups on a local system; however, the commands do not change name service maps or tables. The table below describes the Solaris command used to manage user accounts and groups if you are not using AdminSuite 2.3 or Admintool.
Table 2-5 Managing User Accounts and Groups by Using Solaris Commands
Task |
If You Use This Name Service ... |
Then Use These Commands |
---|---|---|
Add a User Account |
NIS+ |
nistbladm nisclient |
|
NIS |
useradd make |
|
None |
useradd |
Modify a User Account |
NIS+ |
nistbladm |
|
NIS |
usermod make |
|
None |
usermod |
Delete a User Account |
NIS+ |
nistbladm nisclient |
|
NIS |
userdel make |
|
None |
userdel |
Set Up User Account Defaults |
NIS+ |
not available |
|
NIS |
useradd -D make |
|
None |
useradd -D |
Disable a User Account |
NIS+ |
nistbladm |
|
NIS |
passwd -r nis -l make |
|
None |
passwd -r files -l |
Change a User's Password |
NIS+ |
passwd -r nisplus |
|
NIS |
passwd -r nis |
|
None |
passwd -r files |
Sort User Accounts |
NIS+ |
niscat sort |
|
NIS |
ypcat sort |
|
None |
awk sort |
Find a User Account |
NIS+ |
nismatch |
|
NIS |
ypmatch |
|
None |
grep |
Add a Group |
NIS+ |
nistbladm |
|
NIS |
groupadd make |
|
None |
groupadd |
Modify Users in a Group |
NIS+ |
nistbladm |
|
NIS |
groupmod make |
|
None |
groupmod |
Delete a Group |
NIS+ |
nistbladm |
|
NIS |
groupdel make |
|
None |
groupdel |
Admintool is a graphical user interface that enables you to set up user accounts on a local system.
Unless you define a user name or UID number that conflicts with an existing one, you should never need to modify a user account's login name or UID number. Use the following steps if two user accounts have duplicate user names or UID numbers:
If two user accounts have duplicate UID numbers, use Admintool to remove one account and re-add it with a different UID number. You cannot use Admintool to modify a UID number of an existing user account.
If two user account have duplicate user names, use Admintool to modify one of the accounts and change the user name.
If you do use Admintool to change a user name, the home directory's ownership is changed (if a home directory exists for the user).
One part of a user account that you can change is a user's group memberships. Admintool's Modify option lets you add or delete a user's secondary groups. Alternatively, you can use the Groups window to directly modify a group's member list.
You can also modify the following parts of a user account:
Comment
Login shell
Passwords
Home directory
When you delete a user account with Admintool, the software deletes the entries in the passwd and group files. In addition, you can delete the files in the user's home directory.
Although you can't create customized user initialization files with Admintool, you can populate a user's home directory with user initialization files located in a specified "skeleton" directory.
You can customize the user initialization templates in the /etc/skel directory and then copy them to users' home directories.
You can use Admintool for password administration, which includes specifying a normal password for a user account, enabling users to create their own passwords during their first login, disabling or locking a user account, or specifying expiration dates and password aging information.
Password aging is not supported by the NIS name service.
Occasionally, you might need to temporarily or permanently disable a login account. Disabling or locking a user account means that an invalid password, *LK*, is assigned to the user account, preventing future logins.
The easiest way to disable a user account is to use Admintool to lock the password for an account. You can also enter an expiration date in the Expiration Date field to set how long the user account is disabled.
Other ways to disable a user account is to set up password aging or to change the user's password.
Depending on your site policy, you can store user account and group information in a name service or a local system's /etc files. In the NIS+ name service, information is stored in tables, and in the NIS name service, information is stored in maps.
To avoid confusion, the location of the user account and group information is generically referred to as a file rather than a file, table, or map.
Most of the user account information is stored in the passwd file. However, password encryption and password aging is stored in the passwd file when using NIS or NIS+ and in the /etc/shadow file when using /etc files. Password aging is not available when using NIS.
Group information is stored in the group file.
The fields in the passwd file are separated by colons and contain the following information:
username:password:uid:gid:comment:home-directory:login-shell |
For example:
kryten:x:101:100:Kryten Series 4000 Mechanoid:/export/home/kryten:/bin/csh |
The table below describes the passwd file fields.
Table 2-6 Fields in the passwd File
Field Name |
Description |
---|---|
username |
Contains the user or login name. User names should be unique and consist of 1-8 letters (A-Z, a-z) and numerals (0-9). The first character must be a letter, and at least one character must be a lowercase letter. User names cannot contain underscores or spaces. |
password |
Contains an x, a placeholder for the encrypted password. The encrypted password is stored in the shadow file. |
uid |
Contains a user identification (UID) number that identifies the user to the system. UID numbers for regular users should range from 100 to 60000. All UID numbers should be unique. |
gid |
Contains a group identification (GID) number that identifies the user's primary group. Each GID number must be a whole number between 0 and 60002 (60001 and 60002 are assigned to nobody and noaccess, respectively). |
Usually contains the full name of the user. (This field is informational only.) It is sometimes called the GECOS field because it was originally used to hold the login information needed to submit batch jobs to a mainframe running GECOS (General Electric Computer Operating System) from UNIX systems at Bell Labs. |
|
home-directory |
Contains user's home directory path name. |
login-shell |
Contains the user's default login shell, which can be /bin/sh, /bin/csh or /bin/ksh. Table 2-13 contains a description of shell features. |
The default Solaris passwd file contains entries for standard daemons, processes usually started at boot time to perform some system-wide task, such as printing, network administration, and port monitoring.
root:x:0:1:Super-User:/:/sbin/sh daemon:x:1:1::/: bin:x:2:2::/usr/bin: sys:x:3:3::/: adm:x:4:4:Admin:/var/adm: lp:x:71:8:Line Printer Admin:/usr/spool/lp: uucp:x:5:5:uucp Admin:/usr/lib/uucp: nuucp:x:9:9:uucp Admin:/var/spool/uucppublic:/usr/lib/uucp/uucico listen:x:37:4:Network Admin:/usr/net/nls: nobody:x:60001:60001:Nobody:/: noaccess:x:60002:60002:No Access User:/: nobody4:x:65534:65534:SunOS 4.x Nobody:/: |
User Name |
User ID |
Description |
---|---|---|
root |
0 |
Superuser account |
daemon |
1 |
Umbrella system daemon associated with updating calendars, and so forth |
bin |
2 |
Administrative daemon associated with running system binaries to perform some routine system task |
sys |
3 |
Administrative daemon associated with system logging or updating files in temporary directories |
adm |
4 |
Administrative daemon associated with system logging |
|
71 |
Line printer daemon |
uucp |
5 |
uucp daemon |
nuucp |
6 |
uucp daemon |
listen |
37 |
Network listener daemon |
nobody |
60001 |
Anonymous user account, assigned by an NFS server when a request is received from an unauthorized root user. The nobody user account is assigned to software processes that do not need nor should have any special permissions. |
noaccess |
60002 |
Account assigned to a user or a process that needs access to a system through some application but without actually logging in. |
nobody4 |
65534 |
SunOS 4.0 or 4.1 version of nobody user account. |
The fields in the shadow file are separated by colons and contain the following information:
username:password:lastchg:min:max:warn:inactive:expire |
For example:
rimmer:86Kg/MNT/dGu.:8882:0::5:20:8978 |
The table below describes the shadow file fields.
Table 2-8 Fields in the shadow File
The fields in the group file are separated by colons and contain the following information:
group-name:group-password:gid:user-list |
For example:
bin::2:root,bin,daemon |
The table below describes the group file fields.
Table 2-9 Fields in the group File
The default Solaris group file contains the following system groups that support some system-wide task, such as printing, network administration, and electronic mail. Many of these having corresponding entries in the passwd file.
root::0:root other::1: bin::2:root,bin,daemon sys::3:root,bin,sys,adm adm::4:root,adm,daemon uucp::5:root,uucp mail::6:root tty::7:root,tty,adm lp::8:root,lp,adm nuucp::9:root,nuucp staff::10: daemon::12:root,daemon sysadmin::14:root nobody::60001: noaccess::60002: nogroup::65534: |
Group Name |
Group ID |
Description |
---|---|---|
root |
0 |
Superuser group |
other |
1 |
|
bin |
2 |
Administrative group associated with running system binaries |
sys |
3 |
Administrative group associated with system logging or temporary directories |
adm |
4 |
Administrative group associated with system logging |
uucp |
5 |
Group associated with uucp functions |
|
6 |
Electronic mail group |
tty |
7 |
Group associated with tty devices |
|
8 |
Line printer group |
nuucp |
9 |
Group associated with uucp functions |
staff |
10 |
General administrative group |
daemon |
12 |
Daemon group |
sysadmin |
14 |
Administratve group associated with Admintool and Solstice AdminSuite tools |
nobody |
60001 |
Anonymous group assigned by an NFS server when a request is received from an unauthorized root user |
noaccess |
60002 |
|
nogroup |
65534 |
|
Part of setting up a user's home directory is providing user initialization files for the user's login shell. A user initialization file is a shell script that sets up a work environment for a user after the user logs in to a system. Basically, you can perform any task in a user initialization file that you can do in a shell script, but its primary job is to define the characteristics of a user's work environment, such as a user's search path, environment variables, and windowing environment. Each login shell has its own user initialization file (or files), which are listed in the table below.
Table 2-11 User Initialization Files for Bourne, C, and Korn Shells
Shell |
User Initialization File |
Purpose |
---|---|---|
$HOME/.profile |
Defines user's environment at login
|
|
$HOME/.cshrc |
Defines user's environment for all C shells; invoked after login shell |
|
|
Defines user's environment at login
|
|
Defines user's environment at login |
||
|
Defines user's environment at login in the file; specified by the Korn shell's ENV environment variable |
The Solaris environment provides default user initialization files for each shell in the /etc/skel directory on each system, as shown in the table below.
Table 2-12 Default User Initialization Files
Shell |
Default File |
---|---|
| |
You can use these files as a starting point and modify them to create a standard set of files that provide the work environment common to all users, or you can modify them to provide the working environment for different types of users. See "How to Customize User Initialization Files" for step-by-step instructions on how to create sets of user initialization files for different types of users.
When you use Admintool to create a new user account and select the create home directory option, the following files are created, depending on which login shell is selected:
Shell |
Files Created |
---|---|
C |
The /etc/skel/local.cshrc and the /etc/skel/local.login files are copied into the user's home directory and are renamed .cshrc and .login. |
Bourne and Korn |
The /etc/skel/local.profile file is copied into the user's home directory and renamed .profile. |
If you use the useradd command to add a new user account and specify the /etc/skel directory by using the -k and -m options, all three /etc/skel/local* and /etc/skel/.profile files are copied into the user's home directory. At this point, you'll need to rename them to whatever is appropriate for the user's login shell.
The user initialization files can be customized by both the administrator and the user. This important feature can be accomplished with centrally located and globally distributed user initialization files, called site initialization files. Site initialization files enable you to continually introduce new functionality to the user's work environment, while enabling the user to customize the user's initialization file.
When you reference a site initialization file in a user initialization file, all updates to the site initialization file are automatically reflected when the user logs in to the system or when a user starts a new shell. Site initialization files are designed for you to distribute site-wide changes to users' work environments that you did not anticipate when you added the users.
Any customization that can be done in a user initialization file can be done in a site initialization file. These files typically reside on a server (or set of servers), and appear as the first statement in a user initialization file. Also, each site initialization file must be the same type of shell script as the user initialization file that references it.
To reference a site initialization file in a C-shell user initialization file, place a line similar to the following at the beginning of the user initialization file:
source /net/machine-name/export/site-files/site-init-file |
To reference a site initialization file in a Bourne- or Korn-shell user initialization file, place a line similar to the following at the beginning of the user initialization file:
. /net/machine-name/export/site-files/site-init-file |
You should not add specific references to the local system in the user's initialization file. You want the instructions in a user initialization file to be valid regardless of the system to which the user logs in. For example:
To make a user's home directory available anywhere on the network, always refer to the home directory with the variable $HOME. For example, use $HOME/bin; do not use /export/home/username/bin. $HOME works when the user logs in to another system, when home directories are automounted.
To access files on a local disk, use global path names, like /net/machine-name/directory-name. Any directory referenced by /net/machine-name can be mounted automatically on any system on which the user logs in, assuming the system is running AutoFS.
The table below lists basic shell features that each shell provides, which can help you determine what you can and can't do when creating user initialization files for each shell.
Table 2-13 Basic Features of Bourne, C, and Korn Shells
Feature |
Bourne |
C |
Korn |
---|---|---|---|
Known as the standard shell in UNIX |
Yes |
No |
No |
Compatible syntax with Bourne shell |
- |
No |
Yes |
Job control |
Yes |
Yes |
Yes |
History list |
No |
Yes |
Yes |
Command-line editing |
No |
Yes |
Yes |
Aliases |
No |
Yes |
Yes |
Single-character abbreviation for login directory |
No |
Yes |
Yes |
Protection from overwriting (noclobber) |
No |
Yes |
Yes |
Setting to ignore Control-d (ignoreeof) |
No |
Yes |
Yes |
Enhanced cd |
No |
Yes |
Yes |
Initialization file separate from .profile |
No |
Yes |
Yes |
Logout file |
No |
Yes |
A shell maintains an environment that includes a set of variables defined by the login program, the system initialization file, and the user initialization files. In addition, some variables are defined by default. A shell can have two types of variables:
Environment variables - Variables that are exported to all processes spawned by the shell. Their settings can be seen with the env command. A subset of environment variables, like PATH, affects the behavior of the shell itself.
Shell (local) variables - Variables that affect only the current shell. In the C shell, a set of these shell variables have a special relationship to a corresponding set of environment variables. These shell variables are user, term, home, and path. The value of the environment variable counterpart is initially used to set the shell variable.
In the C shell, you use the lowercase names with the set command to set shell variables and use uppercase names with the setenv command to set environment variables. If you set a shell variable, the shell sets the corresponding environment variable and vice versa. For example, if you update the path shell variable with a new path, the shell also updates the PATH environment variable with the new path.
In the Bourne and Korn shells, you use the uppercase names with the setenv command to set both shell and environment variables. You also have to use the export command to finish setting environment variables. For all shells, you generally refer to shell and environment variables by their uppercase names.
In a user initialization file, you can customize a user's shell environment by changing the values of the predefined variables or by specifying additional variables. The table below shows how to set environment variables in a user initialization file.
Table 2-14 Setting Environment Variables in a User Initialization File
If You Want to Set a User's Environment Variables for The ... |
Then Add the Following Line to the User Initialization File ... |
---|---|
setenv MAIL /var/mail/ripley |
|
VARIABLE=value; export VARIABLE Example: MAIL=/var/mail/ripley;export MAIL |
The table below describes environment and shell variables you might want to customize in a user initialization file. For more information about variables used by the different shells, see sh(1), ksh(1), or csh(1).
Table 2-15 Shell and Environment Variable Descriptions
When the user executes a command by using the full path, the shell uses that path to find the command. However, when users specify only a command name, the shell searches the directories for the command in the order specified by the PATH variable. If the command is found in one of the directories, the shell executes it.
A default path is set by the system, but most users modify it to add other command directories. Many user problems related to setting up the environment and accessing the right version of a command or a tool can be traced to incorrectly defined paths.
Here are some guidelines for setting up efficient PATH variables:
If security is not a concern, put the current working directory (.) first in the path. However, including the current working directory in the path poses a security risk that you might want to avoid, especially for superuser.
Keep the search path as short as possible. The shell searches each directory in the path. If a command is not found, long searches can slow down system performance.
The search path is read from left to right, so you should put directories for commonly used commands at the beginning of the path.
Make sure directories are not duplicated in the path.
Avoid searching large directories, if possible. Put large directories at the end of the path.
Put local directories before NFSTM mounted directories to lessen the chance of "hanging" when the NFS server does not respond and to reduce unnecessary network traffic.
The following examples show how to set a user's default path to include the home directory and other NFS mounted directories (the current working directory is specified first in the path). In a C-shell user initialization file, you would add the following:
set path=(. /usr/bin $HOME/bin /net/glrr/files1/bin) |
In a Bourne- or Korn-shell user initialization file, you would add the following:
PATH=.:/usr/bin:/$HOME/bin:/net/glrr/files1/bin export PATH |
The LANG and LC environment variables specify the locale-specific conversions and conventions for the shell, like time zones, collation orders, and formats of dates, time, currency, and numbers. In addition, you can use the stty command in a user initialization file to set whether the system will support multibyte characters.
LANG sets all possible conversions and conventions for the given locale. If you have special needs, you can set various aspects of localization separately through these LC variables: LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_NUMERIC, LC_MONETARY, and LC_TIME.
The table below describes some of the values for the LANG and LC environment variables.
Table 2-16 Values for LANG and LC Variables
Value |
Locale |
---|---|
de |
German |
fr |
French |
iso_8859_1 |
English and European |
it |
Italian |
japanese |
Japanese |
korean |
Korean |
sv |
Swedish |
tchinese |
Taiwanese |
The following examples show how to set the locale using the LANG environment variables. In a C-shell user initialization file, you would add the following:
setenv LANG DE |
In a Bourne- or Korn-shell user initialization file, you would add the following:
LANG=DE; export LANG |
When you create a file or directory, the default file permissions assigned to the file or directory are controlled by the user mask. The user mask is set by the umask command in a user initialization file. You can display the current value of the user mask by typing umask and pressing Return.
The user mask can be set with a three-digit octal value. The first digit sets permissions for the user; the second sets permissions for group; the third sets permissions for other (also referred to as "world"). Note that if the first digit is zero, it is not displayed. For example, if umask is set to 022, 22 is displayed.
To determine the umask value you want to set, subtract the value of the permissions you want from 666 (for a file) or 777 (for a directory). The remainder is the value to use with the umask command. For example, suppose you want to change the default mode for files to 644 (rw-r--r--). The difference between 666 and 644 is 022, which is the value you would use as an argument to the umask command.
You can also determine the umask value you want to set by using the table below, which shows the file and directory permissions that are created for each of the octal values of umask.
Table 2-17 Permissions for umask Values
umask Octal Value |
File Permissions |
Directory Permissions |
---|---|---|
0 |
rw- |
rwx |
1 |
rw- |
rw- |
2 |
r-- |
r-x |
3 |
r-- |
r-- |
4 |
-w- |
-wx |
5 |
-w- |
-w- |
6 |
--x |
--x |
7 |
--- (none) |
--- (none) |
The following line in a user initialization file sets the default file permissions to rw-rw-rw-.
umask 000 |
The following sections provide examples of user and site initialization files that you can use to start customizing your own initialization files. Many of the examples use system names and paths that you need to change for your particular site.
PATH=$PATH:$HOME/bin:/usr/local/bin:/usr/ccs/bin:. 1 MAIL=/var/mail/$LOGNAME 2 NNTPSERVER=server1 3 MANPATH=/usr/share/man:/usr/local/man 4 PRINTER=printer1 5 umask 022 6 export PATH MAIL NNTPSERVER MANPATH PRINTER 7 |
Defines the user's shell search path.
Defines the path to the user's mail file.
Defines the user's Usenet news server.
Defines the user's search path for man pages.
Defines the user's default printer.
Sets the user's default file creation permissions.
Sets the listed environment variables.
set path=($PATH $HOME/bin /usr/local/bin /usr/ccs/bin) 1 setenv MAIL /var/mail/$LOGNAME 2 setenv NNTPSERVER server1 3 setenv PRINTER printer1 4 alias h history 5 umask 022 6 source /net/server2/site-init-files/site.login 7 |
Defines the user's shell search path.
Defines the path to the user's mail file.
Defines the user's Usenet news server.
Defines the user's default printer.
Creates an alias for the history command (the user will need to type only h to run the history command).
Sets the user's default file creation permissions.
Sets the listed environment variables.
The following shows an example site initialization file in which a user can choose a particular version of an application.
# @(#)site.login main: echo "Application Environment Selection" echo "" echo "1. Application, Version 1" echo "2. Application, Version 2" echo "" echo -n "Type 1 or 2 and press Return to set your application environment: " set choice = $< if ( $choice !~ [1-2] ) then goto main endif switch ($choice) case "1": setenv APPHOME /opt/app-v.1 breaksw case "2": setenv APPHOME /opt/app-v.2 endsw |
This site initialization file could be referenced in a user's .cshrc file (C shell users only) with the following line:
source /net/server2/site-init-files/site.login |
In this line, the site initialization file is named site.login and is located on a server named server2. This line also assumes that the automounter is running on the user's system.