[CentOS] Managing users and passwords

[Les Mikesell]

On 3/23/2011 10:45 PM, Todd Cary wrote:
> I plan to make my current Centos 4 HD a slave and install Centos
> 5.5 on a new HD (master).  Then comes the challenge of of moving
> all of my /home/"user" data to the new master.  I have some
> preliminary questions:
>
> Is this a good strategy for installing Centos 5.5: keep the
> Centos 4 on a slave disk?

It's a reasonable approach if you only have one computer.  Just pick the 
new 1st drive only (and remember your old one is already on the 2nd 
controller) in the installer.

> Will the Centos 5.5 detect the slave disk (Centos 4)?

It will see it at the hardware level but not do anything with it. You'll 
need to figure out the device name or label for the partition (and 
Centos5 will probably call it /dev/sd? instead of hd) and mount it 
somewhere.  You should also be able to configure a dual boot if you wanted.

> Is there a way to move the users, groups and passwords from one
> disk to the new Centos 5.5?

The files /etc/passwd, /etc/shadow, /etc/group, and /etc/gshadow have 
this information.  But don't just copy them over.  The accounts below 
uid 500 belong to the system and may be different between versions or 
depending on the installed software.  You can edit your old entries that 
you have added into the new corresponding files.  Or, for a small number 
of users, just 'adduser -u uid login_name', then 'passwd login_name' to 
set the password.

> IT departments must have servers go down or want to install a new
> version of Linux and have the same challenges.

Normally if there are enough machines/users for this to be a problem, 
there would be a central authentication mechanism like LDAP or active 
directory set up.  Servers for things other than direct login or file 
mapping often don't have many real users, though.

-- 
   Les Mikesell
    lesmikesell at gmail.com