切换 root 时 cannot execute ljy ： NO such file or directory

1、问题 

jd@ubuntu:~$ su -
Password: 
Cannot execute ljy: No such file or directory

2、找原因

cat /etc/passwd

root:x:0:0:root:/root :ljy
daemon:x:-7:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13:proxy:/bin:/bin/sh

3、解决

修改为：/bin/bash

root:x:0:0:root:/root:/bin/bash

jd@ubuntu:~$ su -
Password: 
root@ubuntu:~# ^C

若修改为：/bin/sh

jd@ubuntu:~$ su -
Password: 
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