LOGIN(1)

名称
login - 在系统上启动回话

大纲

login [-p] [-h host] [用户名] [ENV=VAR...]

login [-p] [-h host] -f 用户名

login [-p] -r host

描述

The login program is used to establish a new session with the system. It is normally invoked automatically by responding to the login: prompt on the user's terminal. login may be special to the shell and may not be invoked as a sub-process. When called from a shell, login should be executed as exec login 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 login from any shell but the login shell will produce an error message.

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 login exits and the communications link is severed.

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 passwd(1) for more information.

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 "You have new mail.", "You have mail.", or "No Mail." according to the condition of your mailbox.

Your user and group ID will be set according to their values in the /etc/passwd file. The value for $HOME, $SHELL, $PATH, $LOGNAME, and $MAIL 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.

On some installations, the environmental variable $TERM will be initialized to the terminal type on your tty line, as specified in /etc/ttytype.

命令解释器的初始化脚本也可能执行。请参考手册中相应的章节来获取关于此功能的更多信息。

在登录 shell 中以第一个字符是“*”标注的是子系统登录。给定的主目录将被用于用户实际登录的新文件系统的根。

The login program is NOT responsible for removing users from the utmp file. It is the responsibility of getty(8) and init(8) to clean up apparent ownership of a terminal session. If you use login from the shell prompt without exec, the user you use will continue to appear to be logged in even after you log out of the "subsession".

选项

-f
    不要执行认证，用户已经预认证过。

    Note: In that case, username is mandatory.

-h
    此登录的远程主机名。

-p
    保留环境。

-r
    为 rlogin (远程登录)执行 autologin (自动登录)协议。

The -r, -h and -f options are only used when login is invoked by root.

CAVEATS

This version of login has many compilation options, only some of which may be in use at any particular site.

文件的位置由系统配置决定。

The login program is NOT responsible for removing users from the utmp file. It is the responsibility of getty(8) and init(8) to clean up apparent ownership of a terminal session. If you use login from the shell prompt without exec, the user you use will continue to appear to be logged in even after you log out of the "subsession".

As with any program, login's 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.

配置文件

The following configuration variables in /etc/login.defs change the behavior of this tool:

CONSOLE (string)
    如果定义了，或者是包含设备名(没行一个)的文件的完整路径名，或者是“:”分隔的设备名列表。将只会在这写设备上允许 root 登录。

    如果没有定义，可以在任何设备上使用 root。

    指定的设备时不带 /dev/ 前缀。

CONSOLE_GROUPS (string)
    List of groups to add to the user's 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.

DEFAULT_HOME (boolean)
    如果不能 cd 到主目录时，说明是否允许登录。默认是否。

    If set to yes, the user will login in the root (/) directory if it is not possible to cd to her home directory.

ENV_HZ (string)
    If set, it will be used to define the HZ environment variable when a user login. The value must be preceded by HZ=. A common value on Linux is HZ=100.

ENV_PATH (string)
    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 /bin:/usr/bin) and can be preceded by PATH=. The default value is PATH=/bin:/usr/bin.

ENV_SUPATH (string)
    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 /sbin:/bin:/usr/sbin:/usr/bin) and can be preceded by PATH=. The default value is PATH=/sbin:/bin:/usr/sbin:/usr/bin.

ENV_TZ (string)
    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 TZ= (for example TZ=CST6CDT), or the full path to the file containing the timezone specification (for example /etc/tzname).

    If a full path is specified but the file does not exist or cannot be read, the default is to use TZ=CST6CDT.

ENVIRON_FILE (string)
    如果此文件存在，并且可读，将会从中读取登录环境。所有行都必须是 name=value 的格式。

    以 # 开头的行将视为注释，并被忽略。

ERASECHAR (number)
    Terminal ERASE character (010 = backspace, 0177 = DEL).

    此值可以使用前缀“0”表示八进制，“0x”表示十六进制。

FAIL_DELAY (number)
    登录失败后，等待多少秒才再允许登录。

FAILLOG_ENAB (boolean)
    Enable logging and display of /var/log/faillog login failure info.

FAKE_SHELL (string)
    If set, login will execute this shell instead of the users' shell specified in /etc/passwd.

FTMP_FILE (string)
    如果定义，登录失败会以 utmp 格式记录在此文件中。

HUSHLOGIN_FILE (string)
    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's 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's home directory.

ISSUE_FILE (string)
    如果定义了，此文件将在每次的登录提示之前现实。

KILLCHAR (number)
    Terminal KILL character (025 = CTRL/U).

    此值可以使用前缀“0”表示八进制，“0x”表示十六进制。

LASTLOG_ENAB (boolean)
    允许记录和显示 /var/log/lastlog 登录时间信息。

LOGIN_RETRIES (number)
    密码错误时，重试的最大次数。

LOGIN_STRING (string)
    此字符串用于提示输入密码。默认是 "Password: "，或者翻译了的结果(汉语中翻译为了“密码：”)。如果设置了此变量，提示不会被翻译。

    If the string contains %s, this will be replaced by the user's name.

LOGIN_TIMEOUT (number)
    最大登录时间(以秒为单位)。

LOG_OK_LOGINS (boolean)
    允许记录成功登录。

LOG_UNKFAIL_ENAB (boolean)
    在记录到登录失败时，允许记录未知用户名。

    注意：如果用户不小心将密码输入到了登录名中，记录未知用户名可能是一个安全隐患。

MAIL_CHECK_ENAB (boolean)
    启用登录时检查和现实邮箱状态。

    如果 shell 的启动文件已经检查了邮件("mailx -e" 或者其它同功能的工具)，您应该禁用它。

MAIL_DIR (string)
    邮箱目录。修改或删除用户账户时需要处理邮箱，如果没有指定，将使用编译时指定的默认值。

MAIL_FILE (string)
    定义用户邮箱文件的位置(相对于主目录)。

The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and userdel to create, move, or delete the user's mail spool.

If MAIL_CHECK_ENAB is set to yes, they are also used to define the MAIL environment variable.

MOTD_FILE (string)
    If defined, ":" delimited list of "message of the day" files to be displayed upon login.

NOLOGINS_FILE (string)
    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.

PORTTIME_CHECKS_ENAB (boolean)
    Enable checking of time restrictions specified in /etc/porttime.

QUOTAS_ENAB (boolean)
    Enable setting of resource limits from /etc/limits and ulimit, umask, and niceness from the user's passwd gecos field.

TTYGROUP (string), TTYPERM (string)
    The terminal permissions: the login tty will be owned by the TTYGROUP group, and the permissions will be set to TTYPERM.

    By default, the ownership of the terminal is set to the user's primary group and the permissions are set to 0600.

    TTYGROUP can be either the name of a group or a numeric group identifier.

    If you have a write 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.

TTYTYPE_FILE (string)
    If defined, file which maps tty line to TERM environment parameter. Each line of the file is in a format something like "vt100 tty01".

ULIMIT (number)
    Default ulimit value.

UMASK (number)
    文件模式创建掩码初始化为此值。如果没有指定，掩码初始化为 022。

    useradd and newusers use this mask to set the mode of the home directory they create if HOME_MODE is not set.

    It is also used by login to define users' initial umask. Note that this mask can be overridden by the user's GECOS line (if QUOTAS_ENAB is set) or by the specification of a limit with the K identifier in limits(5).

USERGROUPS_ENAB (boolean)
    如果 uid 和 gid 相同，用户名和主用户名也相同，使非 root 组的组掩码位和属主位相同 (如：022 -> 002, 077 -> 007)。

    If set to yes, userdel will remove the user's group if it contains no more members, and useradd will create by default a group with the name of the user.

文件

/var/run/utmp
    当前登录会话的列表。

/var/log/wtmp
    先前的登录会话列表。

/etc/passwd
    用户账户信息。

/etc/shadow
    安全用户账户信息。

/etc/motd
    System message of the day file.

/etc/nologin
    阻止非 root 用户登录。

/etc/ttytype
    终端类型列表。

$HOME/.hushlogin
    阻止现实系统信息。

/etc/login.defs
    Shadow 密码套件配置。

参见

mail(1), passwd(1), sh(1), su(1), login.defs(5), nologin(5), passwd(5), securetty(5), getty(8).