What Debian version are the different Ubuntu versions based on?

You can find the Debian version on which your Ubuntu version is based in the file: /etc/debian_version

From 10.04 up to 21.04:

Ubuntu            Debian  
21.10  impish     bullseye/ sid   - 11
21.04  hirsute    bullseye/ sid   
20.10  groovy     bullseye/ sid
20.04  focal      bullseye/ sid
19.10  eoan       buster  / sid   - 10
19.04  disco      buster  / sid
18.10  cosmic     buster  / sid
18.04  bionic     buster  / sid
17.10  artful     stretch / sid   - 9
17.04  zesty      stretch / sid
16.10  yakkety    stretch / sid
16.04  xenial     stretch / sid
15.10  wily       jessie  / sid   - 8
15.04  vivid      jessie  / sid
14.10  utopic     jessie  / sid
14.04  trusty     jessie  / sid
13.10  saucy      wheezy  / sid   - 7
13.04  raring     wheezy  / sid
12.10  quantal    wheezy  / sid
12.04  precise    wheezy  / sid
11.10  oneiric    wheezy  / sid
11.04  natty      squeeze / sid   - 6
10.10  maverick   squeeze / sid
10.04  lucid      squeeze / sid

Sid is the development distribution of Debian.

You can find out the contents of the file without installing an entire system by view the sources for the package basefiles on Launchpad.


Unfortunately there is no direct mapping /etc/debian_version as mentioned in Jacob's answer gives a rough idea but it only really reflects one package and said package is a package that is locally modified in Ubuntu so won't be automatically pulled in from Debian.

In particular Ubuntu is often ahead of Debian on core packages like libc6. Trying to install a package built on Ubuntu on a contemporary version of Debian is likely to end up with version errors on libc6.

According to https://superuser.com/questions/407745/wrong-libc6-version-in-debian-squeeze-can-i-go-back Debian squeeze had libc6 2.11 . According to http://web.archive.org/web/20110705212424/http://packages.ubuntu.com/search?keywords=libc6 ubuntu 10.04 lucid also had libc6 2.11 . So the packages for 10.4 lucid are IMO the most likely to work on Squeeze.

Depending on what other libraries your program needs you may well find that a specific build for Debian squeeze is needed.