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1 | .\" Copyright (c) 1993 Michael Haardt (michael@moria.de), Fri Apr 2 11:32:09 MET DST 1993 |
| 2 | .\" | |
| 3 | .\" This is free documentation; you can redistribute it and/or | |
| 4 | .\" modify it under the terms of the GNU General Public License as | |
| 5 | .\" published by the Free Software Foundation; either version 2 of | |
| 6 | .\" the License, or (at your option) any later version. | |
| 7 | .\" | |
| 8 | .\" The GNU General Public License's references to "object code" | |
| 9 | .\" and "executables" are to be interpreted as the output of any | |
| 10 | .\" document formatting or typesetting system, including | |
| 11 | .\" intermediate and printed output. | |
| 12 | .\" | |
| 13 | .\" This manual is distributed in the hope that it will be useful, | |
| 14 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 15 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 16 | .\" GNU General Public License for more details. | |
| 17 | .\" | |
| 18 | .\" You should have received a copy of the GNU General Public | |
| 19 | .\" License along with this manual; if not, write to the Free | |
| 20 | .\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, | |
| 21 | .\" USA. | |
| 22 | .\" | |
| 23 | .\" Modified Sun Jul 25 10:46:28 1993 by Rik Faith (faith@cs.unc.edu) | |
| 24 | .\" Modified Sun Aug 21 18:12:27 1994 by Rik Faith (faith@cs.unc.edu) | |
| 25 | .\" Modified Sun Jun 18 01:53:57 1995 by Andries Brouwer (aeb@cwi.nl) | |
| 26 | .\" Modified Mon Jan 5 20:24:40 MET 1998 by Michael Haardt | |
| 27 | .\" (michael@cantor.informatik.rwth-aachen.de) | |
| 28 | .TH PASSWD 5 1998-01-05 "File formats" "Linux Programmer's Manual" | |
| 29 | .SH NAME | |
| 30 | passwd \- password file | |
| 31 | .SH DESCRIPTION | |
| 32 | .B Passwd | |
| 33 | is a text file, that contains a list of the system's accounts, | |
| 34 | giving for each account some useful information like user ID, | |
| 35 | group ID, home directory, shell, etc. | |
| 36 | Often, it also contains the encrypted passwords for each account. | |
| 37 | It should have general read permission (many utilities, like | |
| 38 | .BR ls (1) | |
| 39 | use it to map user IDs to user names), but write access only for the | |
| 40 | superuser. | |
| 41 | .PP | |
| 42 | In the good old days there was no great problem with this general | |
| 43 | read permission. Everybody could read the encrypted passwords, but the | |
| 44 | hardware was too slow to crack a well-chosen password, and moreover, the | |
| 45 | basic assumption used to be that of a friendly user-community. These days | |
| 46 | many people run some version of the shadow password suite, where | |
| 47 | .I /etc/passwd | |
| 48 | has *'s instead of encrypted passwords, and the encrypted passwords are in | |
| 49 | .I /etc/shadow | |
| 50 | which is readable by the superuser only. | |
| 51 | .PP | |
| 52 | Regardless of whether shadow passwords are used, many sysadmins | |
| 53 | use a star in the encrypted password field to make sure | |
| 54 | that this user can not authenticate him- or herself using a | |
| 55 | password. (But see the Notes below.) | |
| 56 | .PP | |
| 57 | If you create a new login, first put a star in the password field, | |
| 58 | then use | |
| 59 | .BR passwd (1) | |
| 60 | to set it. | |
| 61 | .PP | |
| 62 | There is one entry per line, and each line has the format: | |
| 63 | .sp | |
| 64 | .RS | |
| 65 | account:password:UID:GID:GECOS:directory:shell | |
| 66 | .RE | |
| 67 | .sp | |
| 68 | The field descriptions are: | |
| 69 | .sp | |
| 70 | .RS | |
| 71 | .TP 1.0in | |
| 72 | .I account | |
| 73 | the name of the user on the system. It should not contain capital letters. | |
| 74 | .TP | |
| 75 | .I password | |
| 76 | the encrypted user password or a star. | |
| 77 | .TP | |
| 78 | .I UID | |
| 79 | the numerical user ID. | |
| 80 | .TP | |
| 81 | .I GID | |
| 82 | the numerical primary group ID for this user. | |
| 83 | .TP | |
| 84 | .I GECOS | |
| 85 | This field is optional and only used for informational purposes. | |
| 86 | Usually, it contains the full user name. GECOS means General Electric | |
| 87 | Comprehensive Operating System, which has been renamed to GCOS when | |
| 88 | GE's large systems division was sold to Honeywell. Dennis Ritchie has | |
| 89 | reported: "Sometimes we sent printer output or batch jobs to the GCOS | |
| 90 | machine. The gcos field in the password file was a place to stash the | |
| 91 | information for the $IDENTcard. Not elegant." | |
| 92 | .TP | |
| 93 | .I directory | |
| 94 | the user's $HOME directory. | |
| 95 | .TP | |
| 96 | .I shell | |
| 97 | the program to run at login (if empty, use | |
| 8478ee02 | 98 | .IR /bin/sh ). |
| fea681da MK |
99 | If set to a non-existing executable, the user will be unable to login |
| 100 | through | |
| 101 | .BR login (1). | |
| 102 | .RE | |
| 103 | .SH NOTE | |
| 104 | If you want to create | |
| 105 | user groups, their GIDs must be equal and there must be an entry in | |
| 106 | \fI/etc/group\fP, or no group will exist. | |
| 107 | .PP | |
| 108 | If the encrypted password is set to a star, the user will be unable | |
| 109 | to login using | |
| 110 | .BR login (1), | |
| 111 | but may still login using | |
| 112 | .BR rlogin (1), | |
| 113 | run existing processes and initiate new ones through | |
| 114 | .BR rsh (1), | |
| 115 | .BR cron (1), | |
| 116 | .BR at (1), | |
| 117 | or mail filters, etc. Trying to lock an account by simply changing the | |
| 118 | shell field yields the same result and additionally allows the use of | |
| 119 | .BR su (1). | |
| 120 | .SH FILES | |
| 121 | .I /etc/passwd | |
| 122 | .SH "SEE ALSO" | |
| 123 | .BR login (1), | |
| 124 | .BR passwd (1), | |
| 125 | .BR su (1), | |
| 126 | .BR group (5), | |
| 127 | .BR shadow (5) |