有个疑问，关于login命令

[kuangtuxue]

刚开始学linux没多久，今天发现login命令有些问题
在虚拟机里面装的centos6.5系统，然后在tty终端登录成功之后
如果登录的是root用户，此时再用login命令则会直接退出登录。
如果登录的是普通用户，此时再用login命令尝试登录其他用户就会报错：login incorrect
但是如果退出登录后，随便登录哪个用户都可以……

我就是没搞明白，为什么只有在未登录的情况下才可以正常登录，login命令难道不能实现切换用户的作用吗？必须得先退出？
另外，root用户用login命令为啥会直接登出？？？


这是日志

Mar 28 19:59:31 centos01 unix_chkpwd[3643]: check pass; user unknow
Mar 28 19:59:33 centos01 unix_chkpwd[3644]: check pass; user unknown
Mar 28 19:59:33 centos01 unix_chkpwd[3644]: password check failed for user (cv)
Mar 28 19:59:33 centos01 login: pam_unix(login:auth): authentication failure; logname=cx uid=500 euid=500 tty=tty3 ruser= rhost=  user=cv
Mar 28 19:59:35 centos01 login: FAILED LOGIN 1 FROM (null) FOR cv, Authentication failure

这是pam.d里的login文件

#%PAM-1.0
auth [user_unknown=ignore success=ok ignore=ignore default=bad] pam_securetty.so
auth       include      system-auth
account    required     pam_nologin.so
account    include      system-auth
password   include      system-auth
# pam_selinux.so close should be the first session rule
#session    required     pam_selinux.so close
session    required     pam_loginuid.so
session    optional     pam_console.so
# pam_selinux.so open should only be followed by sessions to be executed in the user context
session    required     pam_selinux.so open
session    required     pam_namespace.so
session    optional     pam_keyinit.so force revoke
session    include      system-auth
-session   optional     pam_ck_connector.sozz

这是pam.d里的system-auth文件

#%PAM-1.0
# This file is auto-generated.
# User changes will be destroyed the next time authconfig is run.
auth        required      pam_env.so
auth        sufficient    pam_fprintd.so
auth        sufficient    pam_unix.so nullok try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet
auth        required      pam_deny.so

account     required      pam_unix.so
account     sufficient    pam_localuser.so
account     sufficient    pam_succeed_if.so uid < 500 quiet
account     required      pam_permit.so

password    requisite     pam_cracklib.so try_first_pass retry=3 type=
password    sufficient    pam_unix.so sha512 shadow nullok try_first_pass use_authtok
password    required      pam_deny.so

session     optional      pam_keyinit.so revoke
session     required      pam_limits.so
session     [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid
session     required      pam_unix.so

[aabbabababaa]

没这样用过login，切换用户，一般用su

[kuangtuxue]

引用 1 楼 aabbabababaa 的回复:

没这样用过login，切换用户，一般用su

我已经知道答案了，这就是命令本身的设置。