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System Administration Guide, Volume I

Where User Account and Group Information Is Stored

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.

Note -

To avoid confusion, the location of the user account and group information will be 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.

Fields in the passwd 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:/export/home/kryten:/bin/csh

Table 1-6 describes the passwd file fields.

Table 1-6 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).

comment

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 1-11 contains a description of shell features.

Fields in the Shadow File

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

Table 1-7 describes the shadow file fields.

Table 1-7 Fields in the shadow File

Field Name 

Description 

username

Contains the user or login name. 

password

May contain the following entries: a 13-character encrypted user password; the string *LK*, which indicates an inaccessible account; or the string NP, which indicates no password for the account.

lastchg

Indicates the number of days between January 1, 1970, and the last password modification date. 

min

Contains the minimum number of days required between password changes. 

max

Contains the maximum number of days the password is valid before the user is prompted to specify a new password. 

inactive

Contains the number of days a user account can be inactive before being locked. 

expire

Contains the absolute date when the user account expires. Past this date, the user cannot log in to the system.

Fields in the Group 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

Table 1-8 describes the group file fields.

Table 1-8 Fields in the group File

Field Name 

Description 

group-name

Contains the name assigned to the group. For example, members of the chemistry department in a university may be called chem. Group names can have a maximum of nine characters.

group-password

Usually contains an asterisk or is empty. The group-password field is a relic of earlier versions of UNIX. If a group has a password, the newgrp command prompts users to enter it. However, there is no utility to set the password.

gid

Contains the group's GID number. It must be unique on the local system, and should be unique across the entire organization. Each GID number must be a whole number between 0 and 60002. Numbers under 100 are reserved for system default group accounts. User defined groups can range from 100 to 60000. (60001 and 60002 are reserved and assigned to nobody and noaccess, respectively.)

user-list

Contains a list of comma-separated list of user names, representing the user's secondary group memberships. Each user can belong to a maximum of 16 secondary groups.

UNIX User Groups

By default, all Solaris 7 systems have these groups: 


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:
nobody::60001:
noaccess::60002:
nogroup::65534: