The best way to edit /etc/passwd, or shadow or group file is to use vipw command. Traditionally (under UNIX and Linux) if you use vi to edit /etc/passwd file and same time a user try to change a password while root editing file, then the user's change will not entered into file. To avoid this problem and to put a lock while editing file, use vipw and vigr command which will edit the files /etc/passwd and /etc/group respectively. If you pass -s option to these command, then they will edit the shadow versions of those files i.e. /etc/shadow and /etc/gshadow, respectively.
The main purpose of locks is to prevent file corruption. Do not use vi or other text editor to edit password file. Syntax:
- vipw -s : Edit /etc/passwd file
- vigr -s : Edit /etc/group file
Where,
- -s : Secure file editing
An example
Login as a root user:
# vipw -s
On other terminal login as normal user (for example vivek) and issue command passwd to change vivek’s password:
$ passwd
(current) UNIX password:
Enter new UNIX password:
Retype new UNIX password:
passwd: Authentication token lock busy
As you see it returned with an error "passwd: Authentication token lock busy"
This will avoid /etc/shadow file corruption.
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{ 4 comments… read them below or add one }
Nice tip. thanks.
I think you need a correction in this article.
vipw will edit /etc/passwd file
vigr will edit /etc/group file
AND
vipw -s will edit /etc/shadow file
vigr -s will edit /etc/gshadow file
Hi Gagan,
I believe the given tip in the forum is correct. You can take a clear look by using vipw -s, it will redirect you to passwd file. I am confident saying, shadow file contains password information in encrypted format, which we wont find using this comand. :)
Sricharan,
I can say with confidence and certainty that Gagan Brahmi was correct about your post, I saw his comment after reading and using the commands you suggested, and my /etc/shadow, and /etc/gshadow file were missing my change, and the passwd and group file still contained he information I was removing while trying to create my first chroot jail.
So to anyone reading this page that is learning linux and creating a chroot jail, only use the vipw, and vigr to edit your passwd and group files. Do not add the -s switch or you will be editing your shadow files and could potentially brick your system.