A super elegant way to migrate user accounts from one Linux server to another

Thanks to nixcraft for his how-to here:

http://www.cyberciti.biz/faq/howto-move-migrate-user-accounts-old-to-new-server/.
I had written a very overcomplicated script to accomplish all this (never underestimate the power of AWK!!!), and this simplified my life immensely :)


Setup UID filter limit:
# export UGIDLIMIT=500
Now copy /etc/passwd accounts to /root/passwd.mig using awk to filter out system account (i.e. only copy user accounts)
# awk -v LIMIT=$UGIDLIMIT -F: '($3>=LIMIT) && ($3!=65534)' /etc/passwd > /root/passwd.mig
Copy /etc/group
# awk -v LIMIT=$UGIDLIMIT -F: '($3>=LIMIT) && ($3!=65534)' /etc/group > /root/group.mig
Copy /etc/shadow
# awk -v LIMIT=$UGIDLIMIT -F: '($3>=LIMIT) && ($3!=65534) {print $1}' /etc/passwd | tee - |egrep -f - /etc/shadow > /root/shadow.mig

If you want the whole enchilada for moving users, here it is. Note: This is to be run AS ROOT from the NEW server (e.g. the server being migrated TO), and expects ssh key exchange to be done between the systems.

Be aware that you can well and hose your systems running things as root, and we hereby expressly disclaim any and all responsibility for any damage or problems of any sort caused by your use of this script. This code is supplied as a convenience and carries NO WARRANTY whatsoever.

#!/bin/bash

# Copyright (c)2010 rbTechnologies, LLC
# By Rubin Bennett <rbennett@thatitguy.com>

# Released under the terms and conditions of the GNU Public License version 2.


# A simple script to assist in server migrations from Linux to Linux

# IP address or hostname of source server (e.g. server your're migrating
# AWAY from
sourceServer=172.16.1.55

function syncusers() {
echo -n "Do you have backups of your existing passwd files? [y|N] "
read
if [ "$REPLY" != "y" ]
then
        echo "Please back your files up and run this script again."
        exit 1
else
        scp $sourceServer:/etc/passwd /tmp/passwd.$sourceServer
        scp $sourceServer:/etc/group /tmp/group.$sourceServer
        scp $sourceServer:/etc/shadow /tmp/shadow.$sourceServer

        # First, make a list of non-system users that need to be moved.

        export UGIDLIMIT=500
        awk -v LIMIT=$UGIDLIMIT -F: '($3 >= LIMIT) && ($3 != 65534)' /tmp/passwd.$sourceServer > /tmp/passwd.mig
        awk -v LIMIT=$UGIDLIMIT -F: '($3 >= LIMIT) && ($3 != 65534)' /tmp/group.$sourceServer >/tmp/group.mig
        awk -v LIMIT=$UGIDLIMIT -F: '($3 >= LIMIT) && ($3 != 65534) { print $1 }' /tmp/passwd.$sourceServer | tee - |egrep -f - /tmp/shadow.$sourceServer > /tmp/shadow.mig

        # Now copy non-duplicate entries in to the new server files...
        while IFS=: read user pass uid gid full home shell
        do
                line="$user:$pass:$uid:$gid:$full:$shell"
                exists=`grep $user /etc/passwd`
                if [ ! -z "$exists" ]
                then
                        echo "Copying entry for user $user to new system"
                        echo $line #>> /etc/passwd
                fi
        done </tmp/passwd.mig

        while IFS=: read group pass gid userlist
        do
                line="$group:$pass:$gid:$userlist"
                exists=`grep $group /etc/group`
                if [ ! -z "$exists" ]
                then
                        echo "Copying entry for group $group to new system"
                        echo $line #>> /etc/passwd
                fi
        done </tmp/group.mig

        while IFS=: read user pass lastchanged minimum maximum warn
        do
                line="$user:$pass:$lastchanged:$minimum:$maximum:$warn"
                exists=`grep $user /etc/passwd`
                if [ ! -z "$exists" ]
                then
                        echo "Copying entry for user $user to new system"
                        echo $line #>> /etc/shadow
                fi
        done </tmp/shadow.mig

fi
}

echo "Copying user accounts and passwords from /etc/passwd"
syncusers

exit 0
echo "Backing up config files"
for file in /etc/httpd/conf/httpd.conf
do
        scp $sourceServer:$file $file
done

echo "Scalix Data"
rsync -av --delete 172.16.1.5:/var/opt/scalix/xx/s/data/ /var/opt/scalix/xx/s/data/
echo "Samba Profiles"
rsync -av --delete 172.16.1.5:/var/lib/samba/profiles/ /var/lib/samba/profiles/
echo "Home directories"
rsync -av --delete 172.16.1.5:/home/ /home/
echo "Named data"
rsync -av --delete --exclude proc 172.16.1.5:/var/named/ /var/named/
echo "Copying webserver data"
rsync -av 172.16.1.5:/var/www/ /var/www/