How do you handle libraries in /usr/lib/x86_64-linux-gnu/<subfolder>

[blackliner]

I am starting off with debian bookworm as a base image, and after utilizing this workaround (thanks @gfrankliu), I now have all required libraries installed.

One of them is libopenblas0, which is getting installed into /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblas.so.0. My program fails with ImportError: libopenblas.so.0: cannot open shared object file: No such file or directory, and I can fix it with these two lines in the containers entrypoint.sh:

echo "/usr/lib/x86_64-linux-gnu/openblas-pthread" > /etc/ld.so.conf.d/openblas.conf
ldconfig

Another way is to set LD_LIBRARY_PATH=/usr/lib/x86_64-linux-gnu/openblas-pthread, which is a bit more convinient with oci_image.

Is there a better way to tell ld about this additional location? How is dpkg doing it?

[gfrankliu]

Some deb packages come with "postinst" scripts. eg: , eg, libopenblas0-pthread_0.3.21+ds-4_amd64.deb, postinst script create those symlinks

#! /bin/sh
set -e

update-alternatives --install /usr/lib/x86_64-linux-gnu/libblas.so.3 \
                    libblas.so.3-x86_64-linux-gnu \
                    /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3 100

update-alternatives --install /usr/lib/x86_64-linux-gnu/liblapack.so.3 \
                    liblapack.so.3-x86_64-linux-gnu \
                    /usr/lib/x86_64-linux-gnu/openblas-pthread/liblapack.so.3 100

update-alternatives --install /usr/lib/x86_64-linux-gnu/libopenblas.so.0 \
                    libopenblas.so.0-x86_64-linux-gnu \
                    /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblas.so.0 100



exit 0

Since rules_distroless only takes the tar files, those libs aren't linked into /usr/lib/x86_64-linux-gnu, that's why your program can't find the shared libs in the standard directories.

I am not sure if there is already a feature request for this, or we will just have to live it with it, and add separate rules to create those symlinks.

[loosebazooka]

Yeah, rules_distroless probably wont have a way of auto applying post-install scripts. You can maintain a custom rule to do it for you for the packages that need it.

[blackliner]

Thanks, makes sense! Do you think there is a path forward using these postinst scripts with a dummy update-alternatives that just creates those symlinks?

For the short term solution, I would guess a similar approach to what you proposed previously should do it?

def symlink_files(name, srcs, from_dir, to_dir, **kwargs):
    """Create relative symlinks for all files in from_dir pointing to to_dir.
    
    For example, assume
        from_dir = /usr/bin
        to_dir   = /usr/local/bin
        touch      /usr/bin/foo.
    ls -al /usr/bin/foo
    lrwxrwxrwx 1 root root 20 /usr/bin/foo -> ../local/bin/foo
    """
    native.genrule(
        name = name,
        srcs = srcs,
        outs = [name + ".tar"],
        cmd = " ; ".join([
            # create a temporary directory and untar the files
            "SCRATCH=$$(mktemp -d )",
            "REALOUT=$$(realpath $@)",
            "mkdir -p $$SCRATCH/bundle",
            'for i in $(SRCS); do tar -xmf "$$i" -C $$SCRATCH/bundle ;done',
            "cd $$SCRATCH/bundle",
            "FROM_DIR=" + from_dir,
            "TO_DIR=" + to_dir,
            # remove leading / from the directories
            "FROM_DIR=$$(echo $$FROM_DIR | sed 's|^/||')",
            "TO_DIR=$$(echo $$TO_DIR | sed 's|^/||')",
            # find relative path from to_dir to from_dir
            "RELATIVE_DIR=$$(realpath --relative-to=$$TO_DIR $$FROM_DIR)",
            # create symlinks and tar the files
            "find $$FROM_DIR -type f,l -exec sh -c \"basename {} | xargs -I % ln -s $$RELATIVE_DIR/% $$TO_DIR/%\" \\;",
            "tar --sort=name --owner=root:0 --group=root:0 --mtime='UTC 2019-01-01' -cf $$REALOUT .",
            "rm -rf $$SCRATCH",
        ]),
        **kwargs
    )

usage:

symlink_files(
    name = "symlink_files",
    from_dir = "/usr/lib/x86_64-linux-gnu/openblas-pthread",
    to_dir = "/usr/lib/x86_64-linux-gnu",
    srcs = [
        "@bookworm//libopenblas0-pthread/amd64",
    ],
)

[blackliner]

@loosebazooka should we close this then as won't fix, or keep it open as a feature request?

[loosebazooka]

Yeah probably won't fix. The post install and symlink stories aren't great. But for the purposes of this project I don't see us dealing with them any time soon.