Here's a typical example:
The part before the hyphen (
2.3.3) is the "upstream version". This is
the version of the release tarball from upstream that the package is
The part after the hyphen (
1ubuntu1) is the packaging revision. But
this splits further into the part before
ubuntu and the part after.
The part before (
1) is the Debian packaging revision the packaging in
Ubuntu is based on. The part after (also
1 in this case) is the Ubuntu
So here's how we can interpret this. The
ubuntu tells us that there
are Ubuntu specific changes that have been made in the package. The
string after it (
1) is the packaging revision assigned by the Ubuntu
developer, and suggests that it has only been modified once. Going
backwards, we can see that this Ubuntu modified package is based on
Debian's package of corosync version
2.3.3-1. The Debian maintainer
has assigned packaging revision
1 also, and his package is based on
corosync's upstream release version
This package has also been modified from Debian, since
present in the version string. It is on the second revision of packaging
modifications in Ubuntu, and these modifications are based on the eighth
Debian maintainer's packaging revision of upstream's 2.4.10 release.
Being in sync
The absence of an
ubuntu string inside the version number tells us
that this package source has not been modified from Debian. We usually
describe this as being "in sync" with Debian, which is a common goal for
us in Ubuntu for most packages. This is the first Debian packaging
revision of upstream haproxy's
Not directly based on Debian
-0ubuntu tells us that this package is not based on Debian's
packaging of upstream release
1.2.8 at all. This may be for a number
of reasons, which cannot be determined solely from the version number:
Ubuntu may have pushed ahead with a newer upstream release of
1.2.8before Debian uploaded it. This can happen when Ubuntu developers have a tighter deadline than Debian for a particular version. For example, since Ubuntu has a faster release cycle than Debian, it may be the case that a Debian maintainer hasn't had time to upload to Debian yet, but an Ubuntu developer wants to make the shorter deadline of an imminent Ubuntu release.
The package doesn't exist in Debian at all. This isn't ideal, but happens for very Ubuntu-specific packages. An example of this is
nvidia-304, which is a "restricted" component binary non-free driver.
Ubuntu developers have decided to deliberately diverge from Debian for some reason. We try to avoid this situation as much as possible, but the situation does exist for some packages.
This follows a common scheme used for updates to a stable release (a Stable Release Update, or SRU), where it is often necessary to "insert" a version in between the version in the stable release and version in a future release, so that upgrades to future releases still work correctly.
Use of this scheme isn't mandatory, but unless an Ubuntu developer is
trying to be misleading, this version string means that the second
Ubuntu modified packaging revision (
ubuntu2) of the first Debian
packaging revision (
-1) of the upstream vsftpd release
3.0.2 has had
one SRU (
.1) applied to it in the
14.04 release. See the wiki page
on security update
for more details of this scheme, which is also the recommended scheme to
use for non-security updates.
Another (possibly more) common pattern you'll see in SRU version numbers is:
This uses the same scheme. But here, "inserting" a version didn't need
14.04 style prefix since the same
1.1.5-3ubuntu3 didn't appear
in multiple releases. So, a little more straightforwardly, this has had
one SRU (
.1) applied to the third (
3) Ubuntu (
of the third (
-3) Debian packaging revision of upstream freeipmi
Comparing version numbers
Underpinning all of this is the definition of how Debian and Ubuntu
package version numbers are compared. A strict ordering is defined in
and familiarity with the scheme is essential for package maintainers.
When in doubt,
dpkg --compare-versions can verify the ordering for
It is useful to know that the way that autosync mechanism prevents
Ubuntu-specific changes from being overwritten is by detecting
ubuntu in the
version string. This is how, for example, no-change rebuilds are automatically
synced over, but regular packages with Ubuntu deltas present are not.
Unfortunately, there are many edge cases which make it difficult to write a comprehensive guide. Here are some that come to mind that you can expect to eventually come across:
Native packages (eg.
dpkg) have no packaging revision and so have no hyphen.
Hyphens are permitted in upstream version numbers, which leads to multiple hyphens in the Debian package version string!
Upstream release tarballs that contain files that cannot be redistributed by Debian or Ubuntu for legal reasons are modified by the maintainer to meet policy, and then grow something like
+dfsgto the "upstream" version string.
A tilde (
~) is defined to sort before anything else, including nothing. So it's used to "insert" a version before a standard one. This is commonly used in PPAs and backports.
Version epochs prefix a number followed by a colon to "reset" version numbers, for example when an upstream version numbering scheme changes and a newer version number would otherwise evaluate "backwards".
No change rebuilds lead to versions numbers like
Versions "in the middle". I've said things like "second" and "eighth" above, but without checking we don't know for example that there wasn't an extra
2.4.10-6.1revision in between
2.4.10-7, so this isn't strictly correct. We can't assume the number of versions that exist between two version strings based just on the version strings. The version numbering system is deliberately designed so that it is always possible to create a new version string in the middle.
Debian non-maintainer uploads (NMUs) use an additional suffix instead of bumping the first part of the packaging revision number as the maintainer would. This is to prevent any conflicts with an upload the maintainer might be preparing, and has the benefit of making it clear to others that an NMU took place.