It is possible to rename a volume group on Linux without rebooting the system and loading up a rescue image. This is very useful if, for example, you have a hard drive from a previous install from which you are trying to move data. The trick is to use the UUID of the volume group, not the volume group name, to rename it. Type as root:
vgrename -v <UUID of conflicting volume group> <New Name>
The “-v” will tell you exactly what is happening during the rename.