LOGIN(1)

名称
login - 在系统上启动回话

大纲

login [-p] [-h host] [username] [ENV=VAR...]

login [-p] [-h host] -f username

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:

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
    阻止显示系统信息。

/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).