课程第13次

botang

按照启动时，所执行功能的多少顺序来排序：
rd.break<systemd.unit=emergency.target<systemd.unit=rescue.target

rd.break是在内存根文件系统中，
emergency.target已经在硬盘根文件系统中了（xfs/ext4/ext3......），但是刚刚切换进去，硬盘根文件系统还是只读的，
rescue.target是emergency.target加上：

1. mount  -o remount,rw /

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只要是硬盘根就要密码，所以要初始化root的密码，必须进入rd.break。

--------------------------
1. rd.break
2. chroot /sysroot
3. mount -o remount,rw /
4. passwd
5. touch /.autorelabel
6. exit
7. reboot
--------------------------------------如果selinux策略出问题：/etc/selinux/config  permisive

---------------------------------------RHEL7里的/sbin/init:

1. [root@server3 grub2]# vim grub.cfg
   
2. [root@server3 grub2]# ls -l /sbin/init
   
3. lrwxrwxrwx. 1 root root 22 Jun 29 05:06 /sbin/init -> ../lib/systemd/systemd
   
4. [root@server3 grub2]#
   

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4 a. A ke rnel and i n itra mfs are loaded from disk.
9 b. All units for the default targ et are started.
3 c. The boot loader presents the user with a menu.
5 d. The ke rnel initial izes and lau nches /sbin/init from the initra mfs.
1 e. The system firmware loads the boot loader.
7 f. The system root file system is mou nted read-on ly on /sys root.
6 g. Basic hardwa re initial ization takes place.
8 h. The root fi le system is switched, and control is passed ove r to a new systemd insta nce.
2 i. The boot loader loads its configuration from disk.
----------------------------------------------------------------------------用以下命令破坏bios+mbr的引导头：

1. [root@desktop3 ~]# dd if=/dev/zero of=/dev/sda bs=446 count=1

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