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passwd(5) [redhat man page]

PASSWD(5)							   File formats 							 PASSWD(5)

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 user names), 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 *'s 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 a star 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 a star 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 or a star. 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 user name. 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 non-existing executable, the user will be unable to login through login(1). NOTE
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 a star, 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(1), 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). FILES
/etc/passwd SEE ALSO
passwd(1), login(1), su(1), group(5), shadow(5) 1998-01-05 PASSWD(5)

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PASSWD(5)						   File Formats and Conversions 						 PASSWD(5)

passwd - the password file DESCRIPTION
/etc/passwd contains one line for each user account, with seven fields delimited by colons (":"). These fields are: o login name o optional encrypted password o numerical user ID o numerical group ID o user name or comment field o user home directory o optional user command interpreter The encrypted password field may be blank, in which case no password is required to authenticate as the specified login name. However, some applications which read the /etc/passwd file may decide not to permit any access at all if the password field is blank. If the password field is a lower-case "x", then the encrypted password is actually stored in the shadow(5) file instead; there must be a corresponding line in the /etc/shadow file, or else the user account is invalid. If the password field is any other string, then it will be treated as an encrypted password, as specified by crypt(3). The comment field is used by various system utilities, such as finger(1). The home directory field provides the name of the initial working directory. The login program uses this information to set the value of the $HOME environmental variable. The command interpreter field provides the name of the user's command language interpreter, or the name of the initial program to execute. The login program uses this information to set the value of the $SHELL environmental variable. If this field is empty, it defaults to the value /bin/sh. FILES
/etc/passwd User account information. /etc/shadow optional encrypted password file /etc/passwd- Backup file for /etc/passwd. Note that this file is used by the tools of the shadow toolsuite, but not by all user and password management tools. SEE ALSO
crypt(3), getent(1), getpwnam(3), login(1), passwd(1), pwck(8), pwconv(8), pwunconv(8), shadow(5), su(1), sulogin(8). shadow-utils 05/25/2012 PASSWD(5)
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