Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

passwd(5) [suse man page]

PASSWD(5)						     Linux Programmer's Manual							 PASSWD(5)

NAME
passwd - password file DESCRIPTION
Passwd is a text file, that contains a list of the system's accounts, giving for each account some useful information like user ID, group ID, home directory, shell, etc. Often, it also contains the encrypted passwords for each account. It should have general read permission (many utilities, like ls(1) use it to map user IDs to usernames), but write access only for the superuser. In the good old days there was no great problem with this general read permission. Everybody could read the encrypted passwords, but the hardware was too slow to crack a well-chosen password, and moreover, the basic assumption used to be that of a friendly user-community. These days many people run some version of the shadow password suite, where /etc/passwd has asterisks (*) instead of encrypted passwords, and the encrypted passwords are in /etc/shadow which is readable by the superuser only. Regardless of whether shadow passwords are used, many sysadmins use an asterisk in the encrypted password field to make sure that this user can not authenticate him- or herself using a password. (But see the Notes below.) If you create a new login, first put an asterisk in the password field, then use passwd(1) to set it. There is one entry per line, and each line has the format: account:password:UID:GID:GECOS:directory:shell The field descriptions are: account the name of the user on the system. It should not contain capital letters. password the encrypted user password, an asterisk (*), or the letter 'x'. (See pwconv(8) for an explanation of 'x'.) UID the numerical user ID. GID the numerical primary group ID for this user. GECOS This field is optional and only used for informational purposes. Usually, it contains the full username. GECOS means General Electric Comprehensive Operating System, which has been renamed to GCOS when GE's large systems division was sold to Honeywell. Dennis Ritchie has reported: "Sometimes we sent printer output or batch jobs to the GCOS machine. The gcos field in the password file was a place to stash the information for the $IDENTcard. Not elegant." directory the user's $HOME directory. shell the program to run at login (if empty, use /bin/sh). If set to a nonexistent executable, the user will be unable to login through login(1). FILES
/etc/passwd NOTES
If you want to create user groups, their GIDs must be equal and there must be an entry in /etc/group, or no group will exist. If the encrypted password is set to an asterisk, the user will be unable to login using login(1), but may still login using rlogin(1), run existing processes and initiate new ones through rsh(1), cron(8), at(1), or mail filters, etc. Trying to lock an account by simply chang- ing the shell field yields the same result and additionally allows the use of su(1). SEE ALSO
login(1), passwd(1), su(1), getpwent(3), getpwnam(3), group(5), shadow(5) COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 1998-01-05 PASSWD(5)

Check Out this Related Man Page

PASSWD(5)						     Linux Programmer's Manual							 PASSWD(5)

NAME
passwd - password file DESCRIPTION
The /etc/passwd file is a text file that describes user login accounts for the system. It should have read permission allowed for all users (many utilities, like ls(1) use it to map user IDs to usernames), but write access only for the superuser. In the good old days there was no great problem with this general read permission. Everybody could read the encrypted passwords, but the hardware was too slow to crack a well-chosen password, and moreover the basic assumption used to be that of a friendly user-community. These days many people run some version of the shadow password suite, where /etc/passwd has an 'x' character in the password field, and the encrypted passwords are in /etc/shadow, which is readable by the superuser only. If the encrypted password, whether in /etc/passwd or in /etc/shadow, is an empty string, login is allowed without even asking for a pass- word. Note that this functionality may be intentionally disabled in applications, or configurable (for example using the "nullok" or "nonull" arguments to pam_unix.so). If the encrypted password in /etc/passwd is "*NP*" (without the quotes), the shadow record should be obtained from an NIS+ server. Regardless of whether shadow passwords are used, many system administrators use an asterisk (*) in the encrypted password field to make sure that this user can not authenticate him- or herself using a password. (But see NOTES below.) If you create a new login, first put an asterisk (*) in the password field, then use passwd(1) to set it. Each line of the file describes a single user, and contains seven colon-separated fields: name:password:UID:GID:GECOS:directory:shell The field are as follows: name This is the user's login name. It should not contain capital letters. password This is either the encrypted user password, an asterisk (*), or the letter 'x'. (See pwconv(8) for an explanation of 'x'.) UID The privileged root login account (superuser) has the user ID 0. GID This is the numeric primary group ID for this user. (Additional groups for the user are defined in the system group file; see group(5)). GECOS This field (sometimes called the "comment field") is optional and used only for informational purposes. Usually, it contains the full username. Some programs (for example, finger(1)) display information from this field. GECOS stands for "General Electric Comprehensive Operating System", which was renamed to GCOS when GE's large systems division was sold to Honeywell. Dennis Ritchie has reported: "Sometimes we sent printer output or batch jobs to the GCOS machine. The gcos field in the password file was a place to stash the information for the $IDENTcard. Not elegant." directory This is the user's home directory: the initial directory where the user is placed after logging in. The value in this field is used to set the HOME environment variable. shell This is the program to run at login (if empty, use /bin/sh). If set to a nonexistent executable, the user will be unable to login through login(1). The value in this field is used to set the SHELL environment variable. FILES
/etc/passwd NOTES
If you want to create user groups, there must be an entry in /etc/group, or no group will exist. If the encrypted password is set to an asterisk (*), the user will be unable to login using login(1), but may still login using rlogin(1), run existing processes and initiate new ones through rsh(1), cron(8), at(1), or mail filters, etc. Trying to lock an account by simply changing the shell field yields the same result and additionally allows the use of su(1). SEE ALSO
login(1), passwd(1), su(1), getpwent(3), getpwnam(3), crypt(3), group(5), shadow(5) COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2012-05-03 PASSWD(5)
Man Page