虚拟机修改root密码

1,挂载虚拟机的img 文件

mount -o loop,offset=$((512*1060290)) vm.img /opt/

chroot /opt

ONE-NODE239:/# df

Filesystem           1K-blocks      Used Available Use% Mounted on

/dev/xvda2             3662668   1127288   2535380  31% /

proc                   3662668   1127288   2535380  31% /proc

sysfs                  3662668   1127288   2535380  31% /sys

debugfs                3662668   1127288   2535380  31% /sys/kernel/debug

udev                   3662668   1127288   2535380  31% /dev

devpts                 3662668   1127288   2535380  31% /dev/pts

proc                   3662668   1127288   2535380  31% /var/lib/ntp/proc

ONE-NODE239:/# ls

bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  sbin  srv  sys  tmp  usr  var

ONE-NODE239:/# 

2，重挂根目录，使之可读写

ONE-NODE239:/# mount -o remount,rw /

3，修改root密码

a,如果此时改root密码出现如下错误

ONE-NODE239:/etc# passwd 

Changing password for root.

New Password: 

Bad password: too simple

Reenter New Password: 

Cannot open /dev/urandom for reading: No such file or directory

Cannot create salt for blowfish crypt

Error: Password NOT changed.

passwd: Authentication token manipulation error

b,请执行以下步骤

exit 

mount --bind /dev/ /opt/dev/

chroot /opt/

ONE-NODE239:/# passwd 

Changing password for root.

New Password: 

Bad password: too simple

Reenter New Password: 

Password changed.

ONE-NODE239:/# 

4,此时修改密码成功,我们需要卸载目录，重挂根，重启机器

 # umount /opt/

umount: /opt: device is busy.

        (In some cases useful info about processes that use

         the device is found by lsof(8) or fuser(1))

卸载报错

umount /opt/dev/

umount /opt

5,重启输入密码，修改成功。