WARNING - still work in progress!!!

Debian 6.0 Squeeze, however I think this doesn't depend on your GNU/Linux distribution.

• Migrating from: ejabberd-2.0.5-x86_84
• Migrating to: ejabberd-2.1.5-3+squeeze1

• dump database at old ejabberd

ejabberdctl backup /tmp/ejabberd.backup

• move backup(eg. by SCP) to new machine, if needed
• change hostname, if needed or got changed, as described in Migrate FAQ
• restore database as shown bellow. Skipping tables can be iterative process:

root@foo:~# sh /etc/init.d/ejabberd stop
root@foo:~# ejabberd debug
[...]
(ejabberd@foo)1> mnesia:restore("/tmp/ejabberd2.backup",[{skip_tables,[disco_publish]}]).
{aborted,{no_exists,user_caps}}
(ejabberd@foo)2> mnesia:restore("/tmp/ejabberd2.backup",[{skip_tables,[disco_publish,user_caps]}]). 
{aborted,{no_exists,user_caps_resources}}
(ejabberd@foo)3> mnesia:restore("/tmp/ejabberd2.backup",[{skip_tables,[disco_publish,user_caps,user_caps_resources]}]).
{atomic,[config,privacy,local_config,passwd,irc_custom,
         roster,last_activity,sr_user,offline_msg,route,motd,acl,s2s,
         vcard,caps_features,sr_group,mod_register_ip,vcard_search,
         motd_users,session,private_storage,pubsub_item,muc_room,
         pubsub_state,iq_response,muc_registered,muc_online_room|...]}
(ejabberd@foo)4>q().

• start ejabberd

root@foo:~# sh /etc/init.d/ejabberd start

• enjoy