According to the main tekkit 2.0 download page, Convenient Inventory is listed in the Mods featured list.
The file is named CI2.2.zip
if it is included in tekkit 2 it should be easy to locate this file
Currently I'm Running;
Ubuntu Server 11.10 x64 (VM)
McMyAdmin (Free)
Craftbukkit 1.0.1 (RB 1597)
Tekkit 1.1.4 (Tekkit.jar renamed to craftbukkit.jar)
and obviously Tekkit Client installed on minecraft client
And it works a dream, except my real pc has only 2gb and so its sluggish when i join the server from the client
I'm not a user of CentOs, but that sounds like you have permissions incorrectly setup...
I'm using;
Ubuntu 11.10 Server x64
McMyAdmin Personal
Tekkit 1.1.4
Craftbukkit 1.0.1
all i done to get Tekkit started was to rename the Tekkit "Server" Jar to craftbukkit.jar