我的系统是基于intel Atom的主板，没有视频卡，可以通过串口（波特率为115200）和以太网端口进行通信。我通过PXE安装了CentOS，安装后系统第一次重新启动。以下是通过串行控制台输出的最后几行。之后通过键盘输入时响应。
[ OK ] Started Notify NFS peers of a restart.
[ OK ] Started Logout off all iSCSI sessions on shutdown.
[ OK ] Reached target Remote File Systems (Pre).
[ OK ] Reached target Remote File Systems.
Starting Permit User Sessions...
Starting Crash recovery kernel arming...
Starting Availability of block devices...
[ OK ] Started System Logging Service.
[ OK ] Started OpenSSH server daemon.
[ OK ] Started Availability of block devices.
[ OK ] Started Permit User Sessions.
[ OK ] Started Job spooling tools.
[ OK ] Started Serial Getty on ttyS0.
[ OK ] Reached target Login Prompts.
[ OK ] Started Command Scheduler.
Starting Terminate Plymouth Boot Screen...
[ OK ] Created slice User Slice of root.
[ OK ] Started Session c1 of user root.
[ 20.825375] fuse init (API version 7.22)
****0`3鎬~x饉****[ 31.791710] XFS (sdb1): Mounting V5 Filesystem
[ 31.875202] XFS (sdb1): Ending clean mount
~x饉[ 48.919242] TCP: lp registered
所以登录提示无法正确输出，无法输入用户名和密码并登录。您可以看到最后一行和最后第三行的开头有一些乱码。我怀疑这些是登录提示，但由于某种原因以异常模式输出。
现在我仍然可以通过ssh登录，并且我检查了serial-getty@服务的状态。
[root@CentOS ~]# systemctl status [email protected]
● [email protected] - Serial Getty on ttyS0
Loaded: loaded (/usr/lib/systemd/system/[email protected]; enabled; vendor preset: disabled)
Active: active (running) since Fri 2015-01-02 00:20:42 CST; 28min ago
Docs: man:agetty(8)
man:systemd-getty-generator(8)
http://0pointer.de/blog/projects/serial-console.html
Main PID: 5242 (agetty)
CGroup: /system.slice/system-serial\x2dgetty.slice/[email protected]
└─5242 /sbin/agetty --keep-baud 115200 ttyS0 linux
Jan 02 00:20:42 CentOS systemd[1]: Started Serial Getty on ttyS0.
所以请大家帮忙并给一些建议。多谢！
答案1
看来我找到原因了ModemManager.service与ttyS0冲突。禁用此服务后，启动过程恢复。