Those not familiar with the term B-side have to go back to the vinyl recording days. Singles were 45 RPM records that on their A-sides usually had a cut from a band's newly released album. Because singles had two sides, the B-sides often had a less known track that didn't appear on the album. Although the B-sides didn't (with some exceptions) achieve the popularity of the tracks on the A-sides, they were more or less bonus material and highly sought after by collectors.

Such "b-sides" will now be available for Ubuntu. Castro together with Mathieu Trudel-Lapierre assembled a PPA for these "killer Bs" that provide a selection of programs that Castro considers needing to be "classy" but couldn't be included in the standard installation due to CD space considerations. A metapackage called b-sides would load the bundle of software. Castro is already considering further packages especially for admins or KDE users.

Castro provided a b-sides list that includes OpenOffice, GNOME Do, Gwibber, Jokosher, Miro, Inkscape, gimp-data-extras and GNOME Scan. To install the apps, Ubuntu users can update their systems' software sources with the PPA and install the b-sides package.