Linux – Common user accounts between linux machines

Agree with SLESKE but to expand on his/her comments, you need to do a couple things first!

In Linux, the libraries that control logging in need to be redirected to use an LDAP backend as oppose to looking things up in /etc/passwd.

If you are using OpenLDAP then you will want to look at two things:

NSCD (Name Server Caching Daemon) which caches the LDAP queries. You will run this on each host where users log in.

NSSLDAP (Name Server Switch for LDAP) this is the glue that causes logins to query NSCD, which in turn, will query LDAP backend or NSSLDAP will query LDAP backend directly if NSCD is stale or not available.

So on each workstation you will need to install OpenLDAP, NSCD, and NSSLDAP if not part of your distribution. OpenLDAP is required to get the client libraries which know how to speak LDAP protocol.

Then you need to make edits to some files:

/etc/nscd.conf This file controls what gets cached. Here is a dump from one of my systems that acts as a Samba server:

    enable-cache            passwd          yes
    positive-time-to-live   passwd          10
    negative-time-to-live   passwd          3
    suggested-size          passwd          211
    check-files             passwd          yes
    persistent              passwd          yes
    shared                  passwd          yes
    max-db-size             passwd          33554432
    auto-propagate          passwd          yes

    enable-cache            group           yes
    positive-time-to-live   group           3600
    negative-time-to-live   group           3
    suggested-size          group           211
    check-files             group           yes
    persistent              group           yes
    shared                  group           yes
    max-db-size             group           33554432
    auto-propagate          group           yes

    enable-cache            hosts           yes
    positive-time-to-live   hosts           3600
    negative-time-to-live   hosts           3
    suggested-size          hosts           211
    check-files             hosts           yes
    persistent              hosts           yes
    shared                  hosts           yes
    max-db-size             hosts           33554432

You'll then need to modify your nsswitch.ldap file (read the DOCs on it, too much to go into here).

ONE VERY IMPORTANT THING!!!!

If your LDAP server is down, you want to make sure the local root account can still log in. Or if one of your workstations is having network issues, you'll want to make sure that you can still log in.

So when my Linux boxes boot up, I have a script that always copies a nsswitch.conf file into place that looks as follows:

passwd: compat group: compat

hosts: files dns networks: files

services: files protocols: files rpc: files ethers: files netmasks: files netgroup: files bootparams: files

automount: files aliases: files

and once I'm ready to use LDAP for logins, I replace the nsswitch.conf file with the following:

passwd: files ldap group: files ldap shadow: files ldap

hosts: files dns networks: files

services: files protocols: files rpc: files ethers: files netmasks: files netgroup: files bootparams: files

automount: files aliases: files

The former allows me to login locally and the latter allows both but due to caching by NSCD, it takes time for NSCD to get stale thus causing login delays or issues.

There is much more to be said on this but this hopefully gets you started.

BTW: I'm the developer of Pozix Linux and the Pozix Linux Small Business Server and we have over 400 Samba systems running much this way!

Agreed, TRS80's comments are valid but here is a script we use to create LDIF files from /etc/passwd files. The resulting LDIF file can be used to populate your LDAP database. You'll need to make sure that if you run this script on multiple workstations that you weed out duplicate account names so that you wind up with unique account names with unique UIDs.

cat /etc/passwd | while read i; do
  uid=`echo $i | cut -d : -f 1`
  uidNumber=`echo $i | cut -d : -f 3`
  gidNumber=`echo $i | cut -d : -f 4`
  gecos=`echo $i | cut -d : -f 5`
  homeDirectory=`echo $i | cut -d : -f 6`
  loginShell=`echo $i | cut -d : -f 6`
  userPassword=`cat /etc/shadow | grep $uid | cut -d : -f 2`

  echo "dn: cn=$gecos,ou=people,dc=mycompany,dc=com"
  echo "objectClass: account"
  echo "objectClass: posixAccount"
  echo "cn: $gecos"
  echo "uid: $uid"
  echo "uidNumber: $uidNumber"
  echo "gidNumber: $gidNumber"
  echo "homeDirectory: $homeDirectory"
  echo "loginShell: $loginShell"
  echo "userPassword: $userPassword"

done

You can create root privileges based on LDAP groups using sudo (see the manual for examples). You can even store your sudo configuration within LDAP.

See this question. Debian and LDAP for sudo