Steps to install innobackupex on Ubuntu:
$ apt-key adv --keyserver keys.gnupg.net --recv-keys 1C4CBDCDCD2EFD2A
Add this to /etc/apt/sources.list, replacing VERSION precise with the name of your distribution:
deb repo.percona.com precise main
deb-src repo.percona.com precise main
Remember to update the local cache:
$ apt-get update
Now you can install Percona XtraBackup with:
$ apt-get install percona-xtrabackup