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Diffstat (limited to 'man/man1/login.1')
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diff --git a/man/man1/login.1 b/man/man1/login.1 new file mode 100644 index 0000000..eaa39db --- /dev/null +++ b/man/man1/login.1 @@ -0,0 +1,489 @@ +'\" t +.\" Title: login +.\" Author: Julianne Frances Haugh +.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/> +.\" Date: 11/08/2022 +.\" Manual: User Commands +.\" Source: shadow-utils 4.13 +.\" Language: English +.\" +.TH "LOGIN" "1" "11/08/2022" "shadow\-utils 4\&.13" "User Commands" +.\" ----------------------------------------------------------------- +.\" * Define some portability stuff +.\" ----------------------------------------------------------------- +.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.\" http://bugs.debian.org/507673 +.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html +.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.ie \n(.g .ds Aq \(aq +.el .ds Aq ' +.\" ----------------------------------------------------------------- +.\" * set default formatting +.\" ----------------------------------------------------------------- +.\" disable hyphenation +.nh +.\" disable justification (adjust text to left margin only) +.ad l +.\" ----------------------------------------------------------------- +.\" * MAIN CONTENT STARTS HERE * +.\" ----------------------------------------------------------------- +.SH "NAME" +login \- begin session on the system +.SH "SYNOPSIS" +.HP \w'\fBlogin\fR\ 'u +\fBlogin\fR [\-p] [\-h\ \fIhost\fR] [\fIusername\fR] [\fIENV=VAR\fR...] +.HP \w'\fBlogin\fR\ 'u +\fBlogin\fR [\-p] [\-h\ \fIhost\fR] \-f \fIusername\fR +.HP \w'\fBlogin\fR\ 'u +\fBlogin\fR [\-p] \-r\ \fIhost\fR +.SH "DESCRIPTION" +.PP +The +\fBlogin\fR +program is used to establish a new session with the system\&. It is normally invoked automatically by responding to the +\fIlogin:\fR +prompt on the user\*(Aqs terminal\&. +\fBlogin\fR +may be special to the shell and may not be invoked as a sub\-process\&. When called from a shell, +\fBlogin\fR +should be executed as +\fBexec login\fR +which will cause the user to exit from the current shell (and thus will prevent the new logged in user to return to the session of the caller)\&. Attempting to execute +\fBlogin\fR +from any shell but the login shell will produce an error message\&. +.PP +The user is then prompted for a password, where appropriate\&. Echoing is disabled to prevent revealing the password\&. Only a small number of password failures are permitted before +\fBlogin\fR +exits and the communications link is severed\&. +.PP +If password aging has been enabled for your account, you may be prompted for a new password before proceeding\&. You will be forced to provide your old password and the new password before continuing\&. Please refer to +\fBpasswd\fR(1) +for more information\&. +.PP +After a successful login, you will be informed of any system messages and the presence of mail\&. You may turn off the printing of the system message file, +/etc/motd, by creating a zero\-length file +\&.hushlogin +in your login directory\&. The mail message will be one of "\fIYou have new mail\&.\fR", "\fIYou have mail\&.\fR", or "\fINo Mail\&.\fR" according to the condition of your mailbox\&. +.PP +Your user and group ID will be set according to their values in the +/etc/passwd +file\&. The value for +\fB$HOME\fR, +\fB$SHELL\fR, +\fB$PATH\fR, +\fB$LOGNAME\fR, and +\fB$MAIL\fR +are set according to the appropriate fields in the password entry\&. Ulimit, umask and nice values may also be set according to entries in the GECOS field\&. +.PP +On some installations, the environmental variable +\fB$TERM\fR +will be initialized to the terminal type on your tty line, as specified in +/etc/ttytype\&. +.PP +An initialization script for your command interpreter may also be executed\&. Please see the appropriate manual section for more information on this function\&. +.PP +A subsystem login is indicated by the presence of a "*" as the first character of the login shell\&. The given home directory will be used as the root of a new file system which the user is actually logged into\&. +.PP +The +\fBlogin\fR +program is NOT responsible for removing users from the utmp file\&. It is the responsibility of +\fBgetty\fR(8) +and +\fBinit\fR(8) +to clean up apparent ownership of a terminal session\&. If you use +\fBlogin\fR +from the shell prompt without +\fBexec\fR, the user you use will continue to appear to be logged in even after you log out of the "subsession"\&. +.SH "OPTIONS" +.PP +\fB\-f\fR +.RS 4 +Do not perform authentication, user is preauthenticated\&. +.sp +Note: In that case, +\fIusername\fR +is mandatory\&. +.RE +.PP +\fB\-h\fR +.RS 4 +Name of the remote host for this login\&. +.RE +.PP +\fB\-p\fR +.RS 4 +Preserve environment\&. +.RE +.PP +\fB\-r\fR +.RS 4 +Perform autologin protocol for rlogin\&. +.RE +.PP +The +\fB\-r\fR, +\fB\-h\fR +and +\fB\-f\fR +options are only used when +\fBlogin\fR +is invoked by root\&. +.SH "CAVEATS" +.PP +This version of +\fBlogin\fR +has many compilation options, only some of which may be in use at any particular site\&. +.PP +The location of files is subject to differences in system configuration\&. +.PP +The +\fBlogin\fR +program is NOT responsible for removing users from the utmp file\&. It is the responsibility of +\fBgetty\fR(8) +and +\fBinit\fR(8) +to clean up apparent ownership of a terminal session\&. If you use +\fBlogin\fR +from the shell prompt without +\fBexec\fR, the user you use will continue to appear to be logged in even after you log out of the "subsession"\&. +.PP +As with any program, +\fBlogin\fR\*(Aqs appearance can be faked\&. If non\-trusted users have physical access to a machine, an attacker could use this to obtain the password of the next person coming to sit in front of the machine\&. Under Linux, the SAK mechanism can be used by users to initiate a trusted path and prevent this kind of attack\&. +.SH "CONFIGURATION" +.PP +The following configuration variables in +/etc/login\&.defs +change the behavior of this tool: +.PP +\fBCONSOLE\fR (string) +.RS 4 +If defined, either full pathname of a file containing device names (one per line) or a ":" delimited list of device names\&. Root logins will be allowed only upon these devices\&. +.sp +If not defined, root will be allowed on any device\&. +.sp +The device should be specified without the /dev/ prefix\&. +.RE +.PP +\fBCONSOLE_GROUPS\fR (string) +.RS 4 +List of groups to add to the user\*(Aqs supplementary groups set when logging in on the console (as determined by the CONSOLE setting)\&. Default is none\&. + +Use with caution \- it is possible for users to gain permanent access to these groups, even when not logged in on the console\&. +.RE +.PP +\fBDEFAULT_HOME\fR (boolean) +.RS 4 +Indicate if login is allowed if we can\*(Aqt cd to the home directory\&. Default is no\&. +.sp +If set to +\fIyes\fR, the user will login in the root (/) directory if it is not possible to cd to her home directory\&. +.RE +.PP +\fBENV_HZ\fR (string) +.RS 4 +If set, it will be used to define the HZ environment variable when a user login\&. The value must be preceded by +\fIHZ=\fR\&. A common value on Linux is +\fIHZ=100\fR\&. +.RE +.PP +\fBENV_PATH\fR (string) +.RS 4 +If set, it will be used to define the PATH environment variable when a regular user login\&. The value is a colon separated list of paths (for example +\fI/bin:/usr/bin\fR) and can be preceded by +\fIPATH=\fR\&. The default value is +\fIPATH=/bin:/usr/bin\fR\&. +.RE +.PP +\fBENV_SUPATH\fR (string) +.RS 4 +If set, it will be used to define the PATH environment variable when the superuser login\&. The value is a colon separated list of paths (for example +\fI/sbin:/bin:/usr/sbin:/usr/bin\fR) and can be preceded by +\fIPATH=\fR\&. The default value is +\fIPATH=/sbin:/bin:/usr/sbin:/usr/bin\fR\&. +.RE +.PP +\fBENV_TZ\fR (string) +.RS 4 +If set, it will be used to define the TZ environment variable when a user login\&. The value can be the name of a timezone preceded by +\fITZ=\fR +(for example +\fITZ=CST6CDT\fR), or the full path to the file containing the timezone specification (for example +/etc/tzname)\&. +.sp +If a full path is specified but the file does not exist or cannot be read, the default is to use +\fITZ=CST6CDT\fR\&. +.RE +.PP +\fBENVIRON_FILE\fR (string) +.RS 4 +If this file exists and is readable, login environment will be read from it\&. Every line should be in the form name=value\&. +.sp +Lines starting with a # are treated as comment lines and ignored\&. +.RE +.PP +\fBERASECHAR\fR (number) +.RS 4 +Terminal ERASE character (\fI010\fR += backspace, +\fI0177\fR += DEL)\&. +.sp +The value can be prefixed "0" for an octal value, or "0x" for an hexadecimal value\&. +.RE +.PP +\fBFAIL_DELAY\fR (number) +.RS 4 +Delay in seconds before being allowed another attempt after a login failure\&. +.RE +.PP +\fBFAILLOG_ENAB\fR (boolean) +.RS 4 +Enable logging and display of +/var/log/faillog +login failure info\&. +.RE +.PP +\fBFAKE_SHELL\fR (string) +.RS 4 +If set, +\fBlogin\fR +will execute this shell instead of the users\*(Aq shell specified in +/etc/passwd\&. +.RE +.PP +\fBFTMP_FILE\fR (string) +.RS 4 +If defined, login failures will be logged in this file in a utmp format\&. +.RE +.PP +\fBHUSHLOGIN_FILE\fR (string) +.RS 4 +If defined, this file can inhibit all the usual chatter during the login sequence\&. If a full pathname is specified, then hushed mode will be enabled if the user\*(Aqs name or shell are found in the file\&. If not a full pathname, then hushed mode will be enabled if the file exists in the user\*(Aqs home directory\&. +.RE +.PP +\fBISSUE_FILE\fR (string) +.RS 4 +If defined, this file will be displayed before each login prompt\&. +.RE +.PP +\fBKILLCHAR\fR (number) +.RS 4 +Terminal KILL character (\fI025\fR += CTRL/U)\&. +.sp +The value can be prefixed "0" for an octal value, or "0x" for an hexadecimal value\&. +.RE +.PP +\fBLASTLOG_ENAB\fR (boolean) +.RS 4 +Enable logging and display of /var/log/lastlog login time info\&. +.RE +.PP +\fBLOGIN_RETRIES\fR (number) +.RS 4 +Maximum number of login retries in case of bad password\&. +.RE +.PP +\fBLOGIN_STRING\fR (string) +.RS 4 +The string used for prompting a password\&. The default is to use "Password: ", or a translation of that string\&. If you set this variable, the prompt will not be translated\&. +.sp +If the string contains +\fI%s\fR, this will be replaced by the user\*(Aqs name\&. +.RE +.PP +\fBLOGIN_TIMEOUT\fR (number) +.RS 4 +Max time in seconds for login\&. +.RE +.PP +\fBLOG_OK_LOGINS\fR (boolean) +.RS 4 +Enable logging of successful logins\&. +.RE +.PP +\fBLOG_UNKFAIL_ENAB\fR (boolean) +.RS 4 +Enable display of unknown usernames when login failures are recorded\&. +.sp +Note: logging unknown usernames may be a security issue if an user enter her password instead of her login name\&. +.RE +.PP +\fBMAIL_CHECK_ENAB\fR (boolean) +.RS 4 +Enable checking and display of mailbox status upon login\&. +.sp +You should disable it if the shell startup files already check for mail ("mailx \-e" or equivalent)\&. +.RE +.PP +\fBMAIL_DIR\fR (string) +.RS 4 +The mail spool directory\&. This is needed to manipulate the mailbox when its corresponding user account is modified or deleted\&. If not specified, a compile\-time default is used\&. The parameter CREATE_MAIL_SPOOL in +/etc/default/useradd +determines whether the mail spool should be created\&. +.RE +.PP +\fBMAIL_FILE\fR (string) +.RS 4 +Defines the location of the users mail spool files relatively to their home directory\&. +.RE +.PP +The +\fBMAIL_DIR\fR +and +\fBMAIL_FILE\fR +variables are used by +\fBuseradd\fR, +\fBusermod\fR, and +\fBuserdel\fR +to create, move, or delete the user\*(Aqs mail spool\&. +.PP +If +\fBMAIL_CHECK_ENAB\fR +is set to +\fIyes\fR, they are also used to define the +\fBMAIL\fR +environment variable\&. +.PP +\fBMOTD_FILE\fR (string) +.RS 4 +If defined, ":" delimited list of "message of the day" files to be displayed upon login\&. +.RE +.PP +\fBNOLOGINS_FILE\fR (string) +.RS 4 +If defined, name of file whose presence will inhibit non\-root logins\&. The contents of this file should be a message indicating why logins are inhibited\&. +.RE +.PP +\fBPORTTIME_CHECKS_ENAB\fR (boolean) +.RS 4 +Enable checking of time restrictions specified in +/etc/porttime\&. +.RE +.PP +\fBQUOTAS_ENAB\fR (boolean) +.RS 4 +Enable setting of resource limits from +/etc/limits +and ulimit, umask, and niceness from the user\*(Aqs passwd gecos field\&. +.RE +.PP +\fBTTYGROUP\fR (string), \fBTTYPERM\fR (string) +.RS 4 +The terminal permissions: the login tty will be owned by the +\fBTTYGROUP\fR +group, and the permissions will be set to +\fBTTYPERM\fR\&. +.sp +By default, the ownership of the terminal is set to the user\*(Aqs primary group and the permissions are set to +\fI0600\fR\&. +.sp +\fBTTYGROUP\fR +can be either the name of a group or a numeric group identifier\&. +.sp +If you have a +\fBwrite\fR +program which is "setgid" to a special group which owns the terminals, define TTYGROUP to the group number and TTYPERM to 0620\&. Otherwise leave TTYGROUP commented out and assign TTYPERM to either 622 or 600\&. +.RE +.PP +\fBTTYTYPE_FILE\fR (string) +.RS 4 +If defined, file which maps tty line to TERM environment parameter\&. Each line of the file is in a format something like "vt100 tty01"\&. +.RE +.PP +\fBULIMIT\fR (number) +.RS 4 +Default +\fBulimit\fR +value\&. +.RE +.PP +\fBUMASK\fR (number) +.RS 4 +The file mode creation mask is initialized to this value\&. If not specified, the mask will be initialized to 022\&. +.sp +\fBuseradd\fR +and +\fBnewusers\fR +use this mask to set the mode of the home directory they create if +\fBHOME_MODE\fR +is not set\&. +.sp +It is also used by +\fBlogin\fR +to define users\*(Aq initial umask\&. Note that this mask can be overridden by the user\*(Aqs GECOS line (if +\fBQUOTAS_ENAB\fR +is set) or by the specification of a limit with the +\fIK\fR +identifier in +\fBlimits\fR(5)\&. +.RE +.PP +\fBUSERGROUPS_ENAB\fR (boolean) +.RS 4 +Enable setting of the umask group bits to be the same as owner bits (examples: 022 \-> 002, 077 \-> 007) for non\-root users, if the uid is the same as gid, and username is the same as the primary group name\&. +.sp +If set to +\fIyes\fR, +\fBuserdel\fR +will remove the user\*(Aqs group if it contains no more members, and +\fBuseradd\fR +will create by default a group with the name of the user\&. +.RE +.SH "FILES" +.PP +/var/run/utmp +.RS 4 +List of current login sessions\&. +.RE +.PP +/var/log/wtmp +.RS 4 +List of previous login sessions\&. +.RE +.PP +/etc/passwd +.RS 4 +User account information\&. +.RE +.PP +/etc/shadow +.RS 4 +Secure user account information\&. +.RE +.PP +/etc/motd +.RS 4 +System message of the day file\&. +.RE +.PP +/etc/nologin +.RS 4 +Prevent non\-root users from logging in\&. +.RE +.PP +/etc/ttytype +.RS 4 +List of terminal types\&. +.RE +.PP +$HOME/\&.hushlogin +.RS 4 +Suppress printing of system messages\&. +.RE +.PP +/etc/login\&.defs +.RS 4 +Shadow password suite configuration\&. +.RE +.SH "SEE ALSO" +.PP +\fBmail\fR(1), +\fBpasswd\fR(1), +\fBsh\fR(1), +\fBsu\fR(1), +\fBlogin.defs\fR(5), +\fBnologin\fR(5), +\fBpasswd\fR(5), +\fBsecuretty\fR(5), +\fBgetty\fR(8)\&. |