initramfs/klibc-utils contains identical binaries

[Benjamin Drung]

```
$ jdupes -r /usr/lib/klibc/bin
Scanning: 38 files, 1 items (in 1 specified)
/usr/lib/klibc/bin/gunzip
/usr/lib/klibc/bin/gzip
/usr/lib/klibc/bin/zcat

/usr/lib/klibc/bin/halt
/usr/lib/klibc/bin/poweroff
/usr/lib/klibc/bin/reboot
```

Please replace these binaries with symlinks to reduce the size of the uncompressed initramfs.

ProblemType: Bug
DistroRelease: Ubuntu 23.04
Package: klibc-utils 2.0.12-1
ProcVersionSignature: Ubuntu 6.2.0-25.25-generic 6.2.13
Uname: Linux 6.2.0-25-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.26.1-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: Unity:Unity7:ubuntu
Date: Mon Jul 24 21:14:36 2023
Dependencies: libklibc 2.0.12-1
InstallationDate: Installed on 2022-03-20 (491 days ago)
InstallationMedia: Ubuntu 21.10 "Impish Indri" - Release amd64 (20211012)
SourcePackage: klibc
UpgradeStatus: Upgraded to lunar on 2023-04-20 (95 days ago)

[Adrien Nader (adrien)]

These are actually hardlinks I think and "cpio -H newc" handles hardlinks properly: they don't result in extra space being used.

(yes, I had also thought they did)

[Thorsten Glaser (mirabilos)]

jdupes normally considers hardlinks as one.

And, indeed, on my Debian system, I see:

-rwxr-xr-x 1 root root 36656 May 27 2021 gunzip*
-rwxr-xr-x 1 root root 36656 May 27 2021 gzip*

These aren’t hardlinks.

And indeed they aren’t hardlinks in the Debian binary package either:

$ paxtar -xOf klibc-utils_2.0.8-6.1_amd64.deb data.tar.xz | xz -d | paxtar -tvf - | fgrep zip
-rwxr-xr-x 1 root root 36656 May 27 2021 ./usr/lib/klibc/bin/gunzip
-rwxr-xr-x 1 root root 36656 May 27 2021 ./usr/lib/klibc/bin/gzip

debian/klibc-utils.install just has:

usr/lib/klibc/bin/*

These get placed there by:

override_dh_auto_install:
        $(MAKE) install $(KLIBC_MAKEFLAGS)

Upstream usr/gzip/Kbuild does hardlink them in the build directory:

$(obj)/gunzip $(obj)/zcat: $(obj)/gzip
        $(call cmd,ln)

The upstream “make install” call causes execution of:

  install -m 755 usr/gzip/gzip usr/gzip/gunzip usr/gzip/zcat ../tmp/usr/lib/klibc/bin

And, indeed, this breaks up the hardlink.

I see two actions arising from this:

① The Debian packaging probably should run something like…

for pkgtopdir in debian/*/; do jdupes -rL "$pkgtopdir"; done

… after installing all the files.

@maximilian attems, are you reading?

② Upstream should probably not use install(1) to install hardlinked files; perhaps recreate the hardlinks in the destination like the BSDs do?

I’ll forward this to the upstream mailing list.

[Ben Hutchings (benh-debian)]

This is fixed upstream with:
https://git.kernel.org/pub/scm/libs/klibc/klibc.git/commit/?id=d16525038612be94cf2573c02eac8c7f76321f62

It's about time to make a new upstream release, so I will aim to do that and the Debian update this week.

[Benjamin Drung (bdrung)]

Thanks for addressing it so quickly.

I marked initramfs-tools as affect. We need to test if the hardlinked files will end up hardlinked in the initramfs.

[Launchpad Janitor (janitor)]

This bug was fixed in the package klibc - 2.0.13-1

---------------
klibc (2.0.13-1) unstable; urgency=medium

  * New upstream version:
    - time: Use clock_* system calls for time-of-day and sleep
      (Closes: #923098)
    - Install command links as appropriate (LP: #2028571)

 -- Ben Hutchings <email address hidden> Mon, 31 Jul 2023 15:04:13 +0200

[Benjamin Drung (bdrung)]

Tested initramfs generated with it:

```
$ schroot-wrapper -c mantic -u root -p initramfs-tools,linux-image-generic,fdupes
(mantic)root@host:~# unmkinitramfs /boot/initrd.img initrd
(mantic)root@host:~# jdupes -r /usr/lib/klibc/bin
Scanning: 38 files, 1 items (in 1 specified)
No duplicates found.
(mantic)root@host:~# jdupes -r initrd/
Scanning: 1760 files, 462 items (in 1 specified)
initrd/main/etc/modprobe.d/amd64-microcode-blacklist.conf
initrd/main/etc/modprobe.d/intel-microcode-blacklist.conf

initrd/main/usr/bin/halt
initrd/main/usr/bin/poweroff
```

So the hard-linked files get de-duplicated in the initramfs.