UNIX for Dummies Questions & Answers

Code:

[root@localhost root]# uname -a
Linux localhost.localdomain 2.4.20-8 #1 Thu Mar 13 17:54:28 EST 2003 i686 i686 i386 GNU/Linux
[root@localhost root]# useradd 4141421248
useradd: invalid user name '4141421248'

why???

The first character has to be alphabetic

passwd(4) – password file (man pages section 4: File Formats) - Sun Microsystems

I don't think so.
Because no rule says that.
And one of my friend told me that can work in his system.

Did you read the man page

username

is the user's login name.

The login (login) and role (role) fields accept a string of no more than eight bytes consisting of characters from the set of alphabetic characters, numeric characters, period (.), underscore (_), and hyphen (-). The first character should be alphabetic and the field should contain at least one lower case alphabetic character. A warning message is displayed if these restrictions are not met.

The login and role fields must contain at least one character and must not contain a colon ( or a newline (\n).

Thank you dinjo_jo for your reply.
I tried that in another computer whose OS is RHEL5.2, and that works!
So I am very confused! Maybe it's because of the difference of the OS.
Can you try that in your computer , and let me know if it works?

It can be different on different OS'es and it can be different on same OS if just configured different. So it makes no sense if everybody here in the forum starts trying it out for you.

Maybe your OS has some password checking config files (via pam) like:

Code:

/etc/pam_pwcheck.conf

or

Code:

/etc/pam.d/common-password

Check your OS for similar configs - maybe there is a hint in your man page for useradd too.

useradd works differently on different variants you will need to figure it out on your machine.