Remove unnecessary ruby-libs package

[y3ti]

Alpine version of ruby image installs unnecessary dependency ruby-libs.

$ docker container run --rm -ti ruby:2.3-alpine /bin/sh -c 'apk -vv info | grep ruby'
ruby-libs-2.3.1-r0 - Libraries necessary to run Ruby
.ruby-rundeps-0 - virtual meta package

$ docker container run --rm -ti ruby:2.3-alpine ruby -v
ruby 2.3.4p301 (2017-03-30 revision 58214) [x86_64-linux-musl]

Currently the image contains two versions of libruby.so: one created during
building process and one installed by apk:

$ docker container run --rm -ti ruby:2.3-alpine /bin/sh -c 'find . -name libruby.so*'
./usr/lib/libruby.so.2.3
./usr/lib/libruby.so.2.3.0
./usr/local/lib/libruby.so
./usr/local/lib/libruby.so.2.3
./usr/local/lib/libruby.so.2.3.0

Ruby uses correct libruby version:

$ docker container run --rm -ti ruby:2.3-alpine /bin/sh -c 'ldd /usr/local/bin/ruby'
/lib/ld-musl-x86_64.so.1 (0x5651cd9e5000)
libruby.so.2.3 => /usr/local/lib/libruby.so.2.3 (0x7ff147d4c000)
libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x5651cd9e5000)

I think we should not install ruby-libs from apk.
This commits removes ruby-libs from .ruby-rundeps.

[tianon]

I'm a little confused -- the actual change in the commits here doesn't seem to match what you've described. 😕 (grep -v libruby vs removing ruby-libs)

If that runDeps block is matching libruby from the ruby-libs package, that likely means we've got a binary compiled against it, which is something we'd need to fix too. 😞

[tianon]

Ah, it's this bit that causes the trouble -- we only know that we're linked against libruby.so.2.3, not the full path to the proper .so file. 😞

$ docker run -it --rm ruby:2.3-alpine sh
/ # scanelf --needed --nobanner --recursive /usr/local | awk '{ gsub(/,/, "\nso:", $2); print "so:" $2 }' | sort -u
so:libc.musl-x86_64.so.1
so:libcrypto.so.1.0.0
so:libffi.so.6
so:libgdbm.so.4
so:libgdbm_compat.so.4
so:libncursesw.so.6
so:libreadline.so.6
so:libruby.so.2.3
so:libssl.so.1.0.0
so:libyaml-0.so.2
so:libz.so.1
/ # 

[y3ti]

Yes, and we have two libruby.so installed.

grep -v libruby removes ruby-libs from dependencies list. My solution is only a workaround and I would like to point at the issue.

[yosifkit]

Thanks for finding the bug, but I would like to find a general solution to apply it to images other than ruby. Many official images that build from source on alpine use these same scanelf lines and might be have a similar problem.

🤔 😢

[ojab]

How about that?

[ojab]

whoops, copypaste error. See this commit, actually.