Get minor version of debian-slim - linux

Question

I am setting up my container creation pipeline and I need to be able to get the major AND minor version of the debian-slim build my container is built on.
I tried the following command:
docker run -it --rm -a stdout --entrypoint lsb_release MyContainer:1.0.0 -a
but that just returns:
Distributor ID: Debian
Description: Debian GNU/Linux 10 (buster)
Release: 10
Codename: buster
No minor version listed.
I have also tried:
docker run -it --rm -a stdout --entrypoint cat MyContainer:1.0.0 "/etc/os-release"
but that only outputs:
PRETTY_NAME="Debian GNU/Linux 10 (buster)"
NAME="Debian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
VERSION_CODENAME=buster
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
again, no minor version.
Is there a way to get the minor version? Does the container OS even know its full version number?

Answer 1

In fact, in the old days on Debian9, you could use lsb_release -a to get the minor version as next:
$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 9.5 (stretch)
Release: 9.5
Codename: stretch
You may know, /usr/bin/lsb_release will finally call /usr/lib/python3/dist-packages/lsb_release.py, the realization diff for this script between debian9 & debian10 made the difference.
In debian9, it's next:
def get_distro_information():
lsbinfo = get_lsb_information()
# OS is only used inside guess_debian_release anyway
for key in ('ID', 'RELEASE', 'CODENAME', 'DESCRIPTION',):
if key not in lsbinfo:
distinfo = guess_debian_release()
distinfo.update(lsbinfo)
return distinfo
else:
return lsbinfo
get_lsb_release will fetch the contents of /etc/lsb-release, but there is no file in debian release, so it returns none. Then the procedure have to fallback to guess_debian_release which will fetch the contents from /etc/debian_version, so you get the minor version.
In debian10, it's next:
def get_distro_information():
lsbinfo = get_os_release()
# OS is only used inside guess_debian_release anyway
for key in ('ID', 'RELEASE', 'CODENAME', 'DESCRIPTION',):
if key not in lsbinfo:
distinfo = guess_debian_release()
distinfo.update(lsbinfo)
return distinfo
else:
return lsbinfo
get_os_release will fetch the contents of /usr/lib/os-release, the contens is next:
PRETTY_NAME="Debian GNU/Linux 10 (buster)"
NAME="Debian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
VERSION_CODENAME=buster
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
As it already get the version, so nolonger fallback to guess_debian_release, so you did not get the minor version. The advantage I guess is if not use guess_debian_release, it will use less IO operation, but in my opinion, really countless (Also maybe some hardcoding for guess).
Finally, as a workaround, on debian10, you could use next to get the same behavior as debian 9:
$ LSB_OS_RELEASE="" lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 10.4 (buster)
Release: 10.4
Codename: buster

Answer 2

Should have looked a bit harder. (Found it right after posting)
Debian does it their own way by putting it in the custom, nonstandard, Debian specific file /etc/debian_version found only on Debian Linux:
docker run -it --rm -a stdout --entrypoint cat MyContainer:1.0.0 "/etc/debian_version"
<rant>Why do they not follow the standard of using lsb_release?</rant>