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diff --git a/man5/passwd.5 b/man5/passwd.5 new file mode 100644 index 0000000..9b9a136 --- /dev/null +++ b/man5/passwd.5 @@ -0,0 +1,160 @@ +.\" Copyright (c) 1993 Michael Haardt (michael@moria.de), +.\" Fri Apr 2 11:32:09 MET DST 1993 +.\" +.\" SPDX-License-Identifier: GPL-2.0-or-later +.\" +.\" Modified Sun Jul 25 10:46:28 1993 by Rik Faith (faith@cs.unc.edu) +.\" Modified Sun Aug 21 18:12:27 1994 by Rik Faith (faith@cs.unc.edu) +.\" Modified Sun Jun 18 01:53:57 1995 by Andries Brouwer (aeb@cwi.nl) +.\" Modified Mon Jan 5 20:24:40 MET 1998 by Michael Haardt +.\" (michael@cantor.informatik.rwth-aachen.de) +.TH passwd 5 2023-02-05 "Linux man-pages 6.05.01" +.SH NAME +passwd \- password file +.SH DESCRIPTION +The +.I /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 +.BR ls (1) +use it to map user IDs to usernames), but write access only for the +superuser. +.PP +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 +.I /etc/passwd +has an \[aq]x\[aq] character in the password field, +and the encrypted passwords are in +.IR /etc/shadow , +which is readable by the superuser only. +.PP +If the encrypted password, whether in +.I /etc/passwd +or in +.IR /etc/shadow , +is an empty string, login is allowed without even asking for a password. +Note that this functionality may be intentionally disabled in applications, +or configurable (for example using the +.RB \[dq] nullok \[dq] +or +.RB \[dq] nonull \[dq] +arguments to +.BR pam_unix (8)). +.PP +If the encrypted password in +.I /etc/passwd +is "\fI*NP*\fP" (without the quotes), +the shadow record should be obtained from an NIS+ server. +.PP +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 themself using a +password. +(But see NOTES below.) +.PP +If you create a new login, first put an asterisk (*) in the password field, +then use +.BR passwd (1) +to set it. +.PP +Each line of the file describes a single user, +and contains seven colon-separated fields: +.PP +.in +4n +.EX +name:password:UID:GID:GECOS:directory:shell +.EE +.in +.PP +The field are as follows: +.TP 12 +.I name +This is the user's login name. +It should not contain capital letters. +.TP +.I password +This is either the encrypted user password, +an asterisk (*), or the letter \[aq]x\[aq]. +(See +.BR pwconv (8) +for an explanation of \[aq]x\[aq].) +.TP +.I UID +The privileged +.I root +login account (superuser) has the user ID 0. +.TP +.I GID +This is the numeric primary group ID for this user. +(Additional groups for the user are defined in the system group file; see +.BR group (5)). +.TP +.I 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, +.BR finger (1)) +display information from this field. +.IP +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." +.TP +.I 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 +.B HOME +environment variable. +.TP +.I shell +This is the program to run at login (if empty, use +.IR /bin/sh ). +If set to a nonexistent executable, the user will be unable to login +through +.BR login (1). +The value in this field is used to set the +.B SHELL +environment variable. +.SH FILES +.I /etc/passwd +.SH NOTES +If you want to create user groups, there must be an entry in +.IR /etc/group , +or no group will exist. +.PP +If the encrypted password is set to an asterisk (*), the user will be unable +to login using +.BR login (1), +but may still login using +.BR rlogin (1), +run existing processes and initiate new ones through +.BR rsh (1), +.BR cron (8), +.BR 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 +.BR su (1). +.SH SEE ALSO +.BR chfn (1), +.BR chsh (1), +.BR login (1), +.BR passwd (1), +.BR su (1), +.BR crypt (3), +.BR getpwent (3), +.BR getpwnam (3), +.BR group (5), +.BR shadow (5), +.BR vipw (8) |