Understanding /etc/passwd

NotionCommotion · 03-30-2014, 11:17 AM

Please help me understand what the following means:

Code:

[Michael@michaels ~]$ grep Michael /etc/passwd
Michael:x:501:501::/home/Michael:/bin/bash
[Michael@michaels ~]$

Below is my understanding:

My username
My shadowed password
My userid
A group id created just for me? When is this number different than my userid?
Why is nothing shown between the two colons? What belongs here?
My home directory
My shell

Code:

[root@michaels Michael]# grep Michael /etc/group
Michael:x:501:
[root@michaels Michael]#

My group name
What is the x for?
My group id
Any other usernames (surprisingly to me, not user ids) separated by commas.

Thanks

kirukan · 03-30-2014, 11:31 AM

If you learn linux, hope your can refer some materials and books rather asking questions here. I think others also will agree with me.
see this link have better explanation or you can check the manpage for /etc/passwd
http://www.cyberciti.biz/faq/underst...d-file-format/

NotionCommotion · 03-30-2014, 11:41 AM

Thanks kirukan, I am using a book (Visual Quickstart Guide), but it didn't address the "User ID Info".

joe_2000 · 03-30-2014, 12:23 PM

I think kirukan's link covers your questions on /etc/password.

The x in /etc/group is a password field again. Yes - there can be group passwords in Linux. I did not know either.
You get an extra group created just for you, and the group id is the same as your userid by default. If that group id is already in use you'll probably get a different one. You can also manually change it.

The other user names are the members of the group

NotionCommotion · 03-30-2014, 12:31 PM

Thanks Joe, Yes, I discovered that groups could have passwords as well. Don't know how they are applied, but guess I will cross that bridge when I have a use for it.

Madhu Desai · 03-30-2014, 12:38 PM

Quote:

Originally Posted by NotionCommotion

Why is nothing shown between the two colons? What belongs here?

Its called GECOS. Simply put its nothing but a comment. Its usually filled by user's full name or employee id.

Code:

# man 5 passwd
# useradd -c "Dummy Doodle McDonalds" dummy
# grep dummy /etc/passwd
dummy:x:502:502:Dummy Doodle McDonalds:/home/dummy:/bin/bash

# finger dummy
Login: dummy          			Name: Dummy Doodle McDonalds
Directory: /home/dummy              	Shell: /bin/bash
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