Apt archive mirrors in Git-LFS

My effort to improve transparency and confidence of public apt archives continues. I started to work on this in “Apt Archive Transparency” in which I mention the debdistget project in passing. Debdistget is responsible for mirroring index files for some public apt archives. I’ve realized that having a publicly auditable and preserved mirror of the apt repositories is central to being able to do apt transparency work, so the debdistget project has become more central to my project than I thought. Currently I track Trisquel, PureOS, Gnuinos and their upstreams Ubuntu, Debian and Devuan.

Debdistget download Release/Package/Sources files and store them in a git repository published on GitLab. Due to size constraints, it uses two repositories: one for the Release/InRelease files (which are small) and one that also include the Package/Sources files (which are large). See for example the repository for Trisquel release files and the Trisquel package/sources files. Repositories for all distributions can be found in debdistutils’ archives GitLab sub-group.

The reason for splitting into two repositories was that the git repository for the combined files become large, and that some of my use-cases only needed the release files. Currently the repositories with packages (which contain a couple of months worth of data now) are 9GB for Ubuntu, 2.5GB for Trisquel/Debian/PureOS, 970MB for Devuan and 450MB for Gnuinos. The repository size is correlated to the size of the archive (for the initial import) plus the frequency and size of updates. Ubuntu’s use of Apt Phased Updates (which triggers a higher churn of Packages file modifications) appears to be the primary reason for its larger size.

Working with large Git repositories is inefficient and the GitLab CI/CD jobs generate quite some network traffic downloading the git repository over and over again. The most heavy user is the debdistdiff project that download all distribution package repositories to do diff operations on the package lists between distributions. The daily job takes around 80 minutes to run, with the majority of time is spent on downloading the archives. Yes I know I could look into runner-side caching but I dislike complexity caused by caching.

Fortunately not all use-cases requires the package files. The debdistcanary project only needs the Release/InRelease files, in order to commit signatures to the Sigstore and Sigsum transparency logs. These jobs still run fairly quickly, but watching the repository size growth worries me. Currently these repositories are at Debian 440MB, PureOS 130MB, Ubuntu/Devuan 90MB, Trisquel 12MB, Gnuinos 2MB. Here I believe the main size correlation is update frequency, and Debian is large because I track the volatile unstable.

So I hit a scalability end with my first approach. A couple of months ago I “solved” this by discarding and resetting these archival repositories. The GitLab CI/CD jobs were fast again and all was well. However this meant discarding precious historic information. A couple of days ago I was reaching the limits of practicality again, and started to explore ways to fix this. I like having data stored in git (it allows easy integration with software integrity tools such as GnuPG and Sigstore, and the git log provides a kind of temporal ordering of data), so it felt like giving up on nice properties to use a traditional database with on-disk approach. So I started to learn about Git-LFS and understanding that it was able to handle multi-GB worth of data that looked promising.

Fairly quickly I scripted up a GitLab CI/CD job that incrementally update the Release/Package/Sources files in a git repository that uses Git-LFS to store all the files. The repository size is now at Ubuntu 650kb, Debian 300kb, Trisquel 50kb, Devuan 250kb, PureOS 172kb and Gnuinos 17kb. As can be expected, jobs are quick to clone the git archives: debdistdiff pipelines went from a run-time of 80 minutes down to 10 minutes which more reasonable correlate with the archive size and CPU run-time.

The LFS storage size for those repositories are at Ubuntu 15GB, Debian 8GB, Trisquel 1.7GB, Devuan 1.1GB, PureOS/Gnuinos 420MB. This is for a couple of days worth of data. It seems native Git is better at compressing/deduplicating data than Git-LFS is: the combined size for Ubuntu is already 15GB for a couple of days data compared to 8GB for a couple of months worth of data with pure Git. This may be a sub-optimal implementation of Git-LFS in GitLab but it does worry me that this new approach will be difficult to scale too. At some level the difference is understandable, Git-LFS probably store two different Packages files — around 90MB each for Trisquel — as two 90MB files, but native Git would store it as one compressed version of the 90MB file and one relatively small patch to turn the old files into the next file. So the Git-LFS approach surprisingly scale less well for overall storage-size. Still, the original repository is much smaller, and you usually don’t have to pull all LFS files anyway. So it is net win.

Throughout this work, I kept thinking about how my approach relates to Debian’s snapshot service. Ultimately what I would want is a combination of these two services. To have a good foundation to do transparency work I would want to have a collection of all Release/Packages/Sources files ever published, and ultimately also the source code and binaries. While it makes sense to start on the latest stable releases of distributions, this effort should scale backwards in time as well. For reproducing binaries from source code, I need to be able to securely find earlier versions of binary packages used for rebuilds. So I need to import all the Release/Packages/Sources packages from snapshot into my repositories. The latency to retrieve files from that server is slow so I haven’t been able to find an efficient/parallelized way to download the files. If I’m able to finish this, I would have confidence that my new Git-LFS based approach to store these files will scale over many years to come. This remains to be seen. Perhaps the repository has to be split up per release or per architecture or similar.

Another factor is storage costs. While the git repository size for a Git-LFS based repository with files from several years may be possible to sustain, the Git-LFS storage size surely won’t be. It seems GitLab charges the same for files in repositories and in Git-LFS, and it is around $500 per 100GB per year. It may be possible to setup a separate Git-LFS backend not hosted at GitLab to serve the LFS files. Does anyone know of a suitable server implementation for this? I had a quick look at the Git-LFS implementation list and it seems the closest reasonable approach would be to setup the Gitea-clone Forgejo as a self-hosted server. Perhaps a cloud storage approach a’la S3 is the way to go? The cost to host this on GitLab will be manageable for up to ~1TB ($5000/year) but scaling it to storing say 500TB of data would mean an yearly fee of $2.5M which seems like poor value for the money.

I realized that ultimately I would want a git repository locally with the entire content of all apt archives, including their binary and source packages, ever published. The storage requirements for a service like snapshot (~300TB of data?) is today not prohibitly expensive: 20TB disks are $500 a piece, so a storage enclosure with 36 disks would be around $18.000 for 720TB and using RAID1 means 360TB which is a good start. While I have heard about ~TB-sized Git-LFS repositories, would Git-LFS scale to 1PB? Perhaps the size of a git repository with multi-millions number of Git-LFS pointer files will become unmanageable? To get started on this approach, I decided to import a mirror of Debian’s bookworm for amd64 into a Git-LFS repository. That is around 175GB so reasonable cheap to host even on GitLab ($1000/year for 200GB). Having this repository publicly available will make it possible to write software that uses this approach (e.g., porting debdistreproduce), to find out if this is useful and if it could scale. Distributing the apt repository via Git-LFS would also enable other interesting ideas to protecting the data. Consider configuring apt to use a local file:// URL to this git repository, and verifying the git checkout using some method similar to Guix’s approach to trusting git content or Sigstore’s gitsign.

A naive push of the 175GB archive in a single git commit ran into pack size limitations:

remote: fatal: pack exceeds maximum allowed size (4.88 GiB)

however breaking up the commit into smaller commits for parts of the archive made it possible to push the entire archive. Here are the commands to create this repository:

git init
git lfs install
git lfs track 'dists/**' 'pool/**'
git add .gitattributes
git commit -m"Add Git-LFS track attributes." .gitattributes
time debmirror --method=rsync --host ftp.se.debian.org --root :debian --arch=amd64 --source --dist=bookworm,bookworm-updates --section=main --verbose --diff=none --keyring /usr/share/keyrings/debian-archive-keyring.gpg --ignore .git .
git add dists project
git commit -m"Add." -a
git remote add origin git@gitlab.com:debdistutils/archives/debian/mirror.git
git push --set-upstream origin --all
for d in pool//; do
echo $d;
time git add $d;
git commit -m"Add $d." -a
git push

The resulting repository size is around 27MB with Git LFS object storage around 174GB. I think this approach would scale to handle all architectures for one release, but working with a single git repository for all releases for all architectures may lead to a too large git repository (>1GB). So maybe one repository per release? These repositories could also be split up on a subset of pool/ files, or there could be one repository per release per architecture or sources.

Finally, I have concerns about using SHA1 for identifying objects. It seems both Git and Debian’s snapshot service is currently using SHA1. For Git there is SHA-256 transition and it seems GitLab is working on support for SHA256-based repositories. For serious long-term deployment of these concepts, it would be nice to go for SHA256 identifiers directly. Git-LFS already uses SHA256 but Git internally uses SHA1 as does the Debian snapshot service.

What do you think? Happy Hacking!

Trisquel on arm64: Ampere Altra

Having had success running Trisquel on the ppc64 Talos II, I felt ready to get an arm64 machine running Trisquel. I have a Ampere Altra Developer Platform from ADLINK, which is a fairly powerful desktop machine. While there were some issues during installation, I’m happy to say the machine is stable and everything appears to work fine.

ISO images for non-amd64 platforms are unfortunately still hidden from the main Trisquel download area, so you will have to use the following procedure to download and extract a netinst ISO image (using debian-installer) and write it to a USB memory device. Another unfortunate problem is that there are no OpenPGP signatures or hash checksums, but below I publish one checksum.

wget -q http://builds.trisquel.org/debian-installer-images/debian-installer-images_20210731+deb11u9+11.0trisquel15_arm64.tar.gz

tar xfa debian-installer-images_20210731+deb11u9+11.0trisquel15_arm64.tar.gz ./installer-arm64/20210731+deb11u9+11/images/netboot/mini.iso

echo '311732519cc8c7c1bb2fe873f134fdafb211ef3bcb5b0d2ecdc6ea4e3b336357  installer-arm64/20210731+deb11u9+11/images/netboot/mini.iso' | sha256sum -c

sudo wipefs -a /dev/sdX

sudo dd if=installer-arm64/20210731+deb11u9+11/images/netboot/mini.iso of=/dev/sdX conv=sync status=progress

Insert the USB stick in a USB slot in the machine, and power up. Press ESCAPE at the BIOS prompt and select the USB device as the boot device. The first problem that hit me was that translations didn’t work, I selected Swedish but the strings were garbled. Rebooting and selecting the default English worked fine. For installation, you need Internet connectivity and I use the RJ45 port closest to VGA/serial which is available as enP5p1s0 in the installer. I wouldn’t connect the BMC RJ45 port to anything unless you understand the security implications.

During installation you have to create a EFI partition for booting, and I ended up with one 1GB EFI partition, one 512GB ext4 partition for / with discard/noatime options, and a 32GB swap partition. The installer did not know about any Trisquel mirrors, but only had the default archive.trisquel.org, so if you need to use a mirror, take a note of the necessary details. The installation asks me about which kernel to install, and I went with the default linux-generic which results in a 5.15 linux-libre kernel. At the end of installation, unfortunately grub failed with a mysterious error message: Unable to install GRUB in dummy. Executing 'grub-install dummy' failed. On another console there is a better error message: failed to register the EFI boot entry. There are some references to file descriptor issues. Perhaps I partitioned the disk in a bad way, or this is a real bug in the installer for this platform. I continued installation, and it appears the installer was able to write GRUB to the device, but not add the right boot menu. So I was able to finish the installation properly, and then reboot and manually type the following GRUB commands: linux (hd0,gpt2)/boot/vmlinuz initrd (hd0,gpt2)/boot/initrd.img boot. Use the GRUB ls command to find the right device. See images below for more information.

Booting and installing GRUB again manually works fine:

root@ampel:~# update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/background.cfg'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.15.0-91-generic
Found initrd image: /boot/initrd.img-5.15.0-91-generic
Found linux image: /boot/vmlinuz-5.15.0-58-generic
Found initrd image: /boot/initrd.img-5.15.0-58-generic
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
Adding boot menu entry for UEFI Firmware Settings ...

During installation I tend to avoid selecting any tasksel components, in part because it didn’t use a local mirror to gain network speed, and in part because I don’t want to generate OpenSSH keys in a possibly outdated environment that is harder to audit and reproducible rebuild than the finally installed system. When I selected the OpenSSH and GNOME tasksel, I get an error, but fortunately using apt get directly is simple.

root@ampel:~# tasksel
Tasksel GNOME failed:
tasksel: apt-get failed (100)
root@ampel:~# apt-get install trisquel-gnome ssh

Graphics in GNOME was slow using the built-in ASPEED AST2500 VGA controller with linux-libre 5.15. There are kernels labeled 64k but I haven’t tested them, and I’m not sure they would bring any significant advantage. I simply upgraded to a more recent linux-libre 6.2 kernel via the linux-image-generic-hwe-11.0 virtual package. After a reboot, graphics in GNOME is usable.

root@ampel:~# apt-get install linux-image-generic-hwe-11.0

There seems to be some issue with power-saving inside GNOME, since the machine becomes unresponsive after 20 minutes, and I’m unable to make it resume via keyboard or power button. Disabling the inactivity power setting in GNOME works fine to resolve this.

I will now put this machine to some more heavy use and see how it handles it. I hope to find more suitable arm64-based servers to complement my ppc64el-based servers in the future, as this ADLINK Ampere Altra Developer Platform with liquid-cooling is more of a toy than a serious server for use in a datacentre.

Happy Trisquel-on-arm64 Hacking!

Validating debian/copyright: licenserecon

Recently I noticed a new tool called licenserecon written by Peter Blackman, and I helped get licenserecon into Debian. The purpose of licenserecon is to reconcile licenses from debian/copyright against the output from licensecheck, a tool written by Jonas Smedegaard. It assumes DEP5 copyright files. You run the tool in a directory that has a debian/ sub-directory, and its output when it notices mismatches (this is for resolv-wrapper):

# sudo apt install licenserecon
jas@kaka:~/dpkg/resolv-wrapper$ lrc

Parsing Source Tree ....
Running licensecheck ....

d/copyright     | licensecheck

BSD-3-Clauses   | BSD-3-clause     src/resolv_wrapper.c
BSD-3-Clauses   | BSD-3-clause     tests/dns_srv.c
BSD-3-Clauses   | BSD-3-clause     tests/test_dns_fake.c
BSD-3-Clauses   | BSD-3-clause     tests/test_res_query_search.c
BSD-3-Clauses   | BSD-3-clause     tests/torture.c
BSD-3-Clauses   | BSD-3-clause     tests/torture.h


Noticing one-character typos like this may not bring satisfaction except to the most obsessive-compulsive among us, however the tool has the potential of discovering more serious mistakes.

Using it manually once in a while may be useful, however I tend to forget QA steps that are not automated. Could we add this to the Salsa CI/CD pipeline? I recently proposed a merge request to add a wrap-and-sort job to the Salsa CI/CD pipeline (disabled by default) and learned how easy it was to extend it. I think licenserecon is still a bit rough on the edges, and I haven’t been able to successfully use it on any but the simplest packages yet. I wouldn’t want to suggest it is added to the normal Salsa CI/CD pipeline, even if disabled. If you maintain a Debian package on Salsa and wish to add a licenserecon job to your pipeline, I wrote licenserecon.yml for you.

The simplest way to use licenserecon.yml is to replace recipes/debian.yml@salsa-ci-team/pipeline as the Salsa CI/CD configuration file setting with debian/salsa-ci.yml@debian/licenserecon. If you use a debian/salsa-ci.yml file you may put something like this in it instead:

  - https://salsa.debian.org/salsa-ci-team/pipeline/raw/master/recipes/debian.yml
  - https://salsa.debian.org/debian/licenserecon/raw/main/debian/licenserecon.yml

Once you trigger the pipeline, this will result in a new job licenserecon that validates debian/copyright against licensecheck output on every build! I have added this to the libcpucycles package on Salsa and the pipeline contains a new job licenserecon whose output currently ends with:

$ lrc
Parsing Source Tree ....
Running licensecheck ....
No differences found
Cleaning up project directory and file based variables

If upstream releases a new version with files not matching our debian/copyright file, we will detect that on the next Salsa build job rather than months later when somebody happens to run the tools manually or there is some license conflict.

Incidentally licenserecon is written in Pascal which brought back old memories with Turbo Pascal back in the MS-DOS days. Thanks Peter for licenserecon, and Jonas for licensecheck making this possible!

Trisquel on ppc64el: Talos II

The release notes for Trisquel 11.0 “Aramo” mention support for POWER and ARM architectures, however the download area only contains links for x86, and forum posts suggest there is a lack of instructions how to run Trisquel on non-x86.

Since the release of Trisquel 11 I have been busy migrating x86 machines from Debian to Trisquel. One would think that I would be finished after this time period, but re-installing and migrating machines is really time consuming, especially if you allow yourself to be distracted every time you notice something that Really Ought to be improved. Rabbit holes all the way down. One of my production machines is running Debian 11 “bullseye” on a Talos II Lite machine from Raptor Computing Systems, and migrating the virtual machines running on that host (including the VM that serves this blog) to a x86 machine running Trisquel felt unsatisfying to me. I want to migrate my computing towards hardware that harmonize with FSF’s Respects Your Freedom and not away from it. Here I had to chose between using the non-free software present in newer Debian or the non-free software implied by most x86 systems: not an easy chose. So I have ignored the dilemma for some time. After all, the machine was running Debian 11 “bullseye”, which was released before Debian started to require use of non-free software. With the end-of-life date for bullseye approaching, it seems that this isn’t a sustainable choice.

There is a report open about providing ppc64el ISOs that was created by Jason Self shortly after the release, but for many months nothing happened. About a month ago, Luis Guzmán mentioned an initial ISO build and I started testing it. The setup has worked well for a month, and with this post I want to contribute instructions how to get it up and running since this is still missing.

The setup of my soon-to-be new production machine:

  • Talos II Lite
  • POWER9 18-core v2 CPU
  • Inter-Tech 4U-4410 rack case with ASPOWER power supply
  • 8x32GB DDR4-2666 ECC RDIMM
  • HighPoint SSD7505 (the Rocket 1504 or 1204 would be a more cost-effective choice, but I re-used a component I had laying around)
  • PERC H700 aka LSI MegaRAID 2108 SAS/SATA (also found laying around)
  • 2x1TB NVMe
  • 3x18TB disks

According to the notes in issue 14 the ISO image is available at https://builds.trisquel.org/debian-installer-images/ and the following commands download, integrity check and write it to a USB stick:

wget -q https://builds.trisquel.org/debian-installer-images/debian-installer-images_20210731+deb11u8+11.0trisquel14_ppc64el.tar.gz
tar xfa debian-installer-images_20210731+deb11u8+11.0trisquel14_ppc64el.tar.gz ./installer-ppc64el/20210731+deb11u8+11/images/netboot/mini.iso
echo '6df8f45fbc0e7a5fadf039e9de7fa2dc57a4d466e95d65f2eabeec80577631b7  ./installer-ppc64el/20210731+deb11u8+11/images/netboot/mini.iso' | sha256sum -c
sudo wipefs -a /dev/sdX
sudo dd if=./installer-ppc64el/20210731+deb11u8+11/images/netboot/mini.iso of=/dev/sdX conv=sync status=progress

Sadly, no hash checksums or OpenPGP signatures are published.

Power off your device, insert the USB stick, and power it up, and you see a Petitboot menu offering to boot from the USB stick. For some reason, the "Expert Install" was the default in the menu, and instead I select "Default Install" for the regular experience. For this post, I will ignore BMC/IPMI, as interacting with it is not necessary. Make sure to not connect the BMC/IPMI ethernet port unless you are willing to enter that dungeon. The VGA console works fine with a normal USB keyboard, and you can chose to use only the second enP4p1s0f1 network card in the network card selection menu.

If you are familiar with Debian netinst ISO’s, the installation is straight-forward. I complicate the setup by partitioning two RAID1 partitions on the two NVMe sticks, one RAID1 for a 75GB ext4 root filesystem (discard,noatime) and one RAID1 for a 900GB LVM volume group for virtual machines, and two 20GB swap partitions on each of the NVMe sticks (to silence a warning about lack of swap, I’m not sure swap is still a good idea?). The 3x18TB disks use DM-integrity with RAID1 however the installer does not support DM-integrity so I had to create it after the installation.

There are two additional matters worth mentioning:

  • Selecting the apt mirror does not have the list of well-known Trisquel mirrors which the x86 installer offers. Instead I have to input the archive mirror manually, and fortunately the archive.trisquel.org hostname and path values are available as defaults, so I just press enter and fix this after the installation has finished. You may want to have the hostname/path of your local mirror handy, to speed things up.
  • The installer asks me which kernel to use, which the x86 installer does not do. I believe older Trisquel/Ubuntu installers asked this question, but that it was gone in aramo on x86. I select the default “linux-image-generic” which gives me a predictable 5.15 Linux-libre kernel, although you may want to chose “linux-image-generic-hwe-11.0” for a more recent 6.2 Linux-libre kernel. Maybe this is intentional debinst-behaviour for non-x86 platforms?

I have re-installed the machine a couple of times, and have now finished installing the production setup. I haven’t ran into any serious issues, and the system has been stable. Time to wrap up, and celebrate that I now run an operating system aligned with the Free System Distribution Guidelines on hardware that aligns with Respects Your Freedom — Happy Hacking indeed!

Enforcing wrap-and-sort -satb

For Debian package maintainers, the wrap-and-sort tool is one of those nice tools that I use once in a while, and every time have to re-read the documentation to conclude that I want to use the --wrap-always --short-indent --trailing-comma --sort-binary-package options (or -satb for short). Every time, I also wish that I could automate this and have it always be invoked to keep my debian/ directory tidy, so I don’t have to do this manually once every blue moon. I haven’t found a way to achieve this automation in a non-obtrusive way that interacts well with my git-based packaging workflow. Ideally I would like for something like the lintian-hook during gbp buildpackage to check for this – ideas?

Meanwhile, I have come up with a way to make sure I don’t forget to run wrap-and-sort for long, and that others who work on the same package won’t either: create an autopkgtest which is invoked during the Salsa CI/CD pipeline using the following as debian/tests/wrap-and-sort:


set -eu

TMPDIR=$(mktemp -d)

cp -a debian $TMPDIR
wrap-and-sort -satb
diff -ur $OLDPWD/debian debian

Add the following to debian/tests/control to invoke it – which is intentionally not indented properly so that the self-test will fail so you will learn how it behaves.

Tests: wrap-and-sort
Depends: devscripts, python3-debian
Restrictions: superficial

Now I will get build failures in the pipeline once I upload the package into Salsa, which I usually do before uploading into Debian. I will get a diff output, and it won’t be happy until I push a commit with the output of running wrap-and-sort with the parameters I settled with.

While autopkgtest is intended to test the installed package, the tooling around autopkgtest is powerful and easily allows this mild abuse of its purpose for a pleasant QA improvement.

Thoughts? Happy hacking!