For convenience, innobackupex has a --copy-back option, which performs the restoration of a backup to the server’s datadir
$ innobackupex --copy-back /path/to/BACKUP-DIR
It will copy all the data-related files back to the server’s datadir, determined by the server’s my.cnf configuration file. You should check the last line of the output for a success message:
innobackupex: Finished copying back files. 111225 01:08:13 innobackupex: completed OK!
As files’ attributes will be preserved, in most cases you will need to change the files’ ownership to mysql before starting the database server, as they will be owned by the user who created the backup:
$ chown -R mysql:mysql /var/lib/mysql
Also note that all of these operations will be done as the user calling innobackupex, you will need write permissions on the server’s datadir.