Search Results: "Stephan Lachnit"

8 February 2023

Stephan Lachnit: Setting up fast Debian package builds using sbuild, mmdebstrap and apt-cacher-ng

In this post I will give a quick tutorial on how to set up fast Debian package builds using sbuild with mmdebstrap and apt-cacher-ng. The usual tool for building Debian packages is dpkg-buildpackage, or a user-friendly wrapper like debuild, and while these are geat tools, if you want to upload something to the Debian archive they lack the required separation from the system they are run on to ensure that your packaging also works on a different system. The usual candidate here is sbuild. But setting up a schroot is tedious and performance tuning can be annoying. There is an alternative backend for sbuild that promises to make everything simpler: unshare. In this tutorial I will show you how to set up sbuild with this backend. Additionally to the normal performance tweaking, caching downloaded packages can be a huge performance increase when rebuilding packages. I do rebuilds quite often, mostly when a new dependency got introduced I didn t specify in debian/control yet or lintian notices a something I can easily fix. So let s begin with setting up this caching.

Setting up apt-cacher-ng Install apt-cacher-ng:
sudo apt install apt-cacher-ng
A pop-up will appear, if you are unsure how to answer it select no, we don t need it for this use-case. To enable apt-cacher-ng on your system, create /etc/apt/apt.conf.d/02proxy and insert:
Acquire::http::proxy "";
Acquire::https::proxy "DIRECT";
In /etc/apt-cacher-ng/acng.conf you can increase the value of ExThreshold to hold packages for a shorter or longer duration. The length depends on your specific use case and resources. A longer threshold takes more disk space, a short threshold like one day effecitvely only reduces the build time for rebuilds. If you encounter weird issues on apt update at some point the future, you can try to clean the cache from apt-cacher-ng. You can use this script:

Setting up mmdebstrap Install mmdebstrap:
sudo apt install mmdebstrap
We will create a small helper script to ease creating a chroot. Open ~/.local/bin/mmupdate and insert:
mmdebstrap \
  --variant=buildd \
  --aptopt='Acquire::http::proxy "";' \
  --arch=amd64 \
  --components=main,contrib,non-free \
  unstable \
  ~/.cache/sbuild/unstable-amd64.tar.xz \
  • aptopt enables apt-cacher-ng inside the chroot.
  • --arch sets the CPU architecture (see Debian Wiki).
  • --components sets the archive components, if you don t want non-free pacakges you might want to remove some entries here.
  • unstable sets the Debian release, you can also set for example bookworm-backports here.
  • unstable-amd64.tar.xz is the output tarball containing the chroot, change accordingly to your pick of the CPU architecture and Debian release.
  • is the Debian mirror, you should set this to the same one you use in your /etc.apt/sources.list.
Make mmupdate executable and run it once:
chmod +x ~/.local/bin/mmupdate
mkdir -p ~/.cache/sbuild
If you execute mmupdate again you can see that the downloading stage is much faster thanks to apt-cacher-ng. For me the difference is from about 115s to about 95s. Your results may vary, this depends on the speed of your internet, Debian mirror and disk. If you have used the schroot backend and sbuild-update before, you probably notice that creating a new chroot with mmdebstrap is slower. It would be a bit annoying to do this manually before we start a new Debian packaging session, so let s create a systemd service that does this for us. First create a folder for user services:
mkdir -p ~/.config/systemd/user
Create ~/.config/systemd/user/mmupdate.service and add:
Description=Run mmupdate
Start the service and test that it works:
systemctl --user daemon-reload
systemctl --user start mmupdate
systemctl --user status mmupdate
Create ~/.config/systemd/user/mmupdate.timer:
Description=Run mmupdate daily
Enable the timer:
systemctl --user enable mmupdate.timer
Now every day mmupdte will be run automatically. You can adjust the period if you think daily rebuilds are a bit excessive. A neat advantage of period rebuilds is that they the base files in your apt-cacher-ng cache warm every time they run.

Setting up sbuild: Install sbuild and (optionally) autopkgtest:
sudo apt install --no-install-recommends sbuild autopkgtest
Create ~/.sbuildrc and insert:
# backend for using mmdebstrap chroots
$chroot_mode = 'unshare';
# build in tmpfs
$unshare_tmpdir_template = '/dev/shm/tmp.sbuild.XXXXXXXX';
# upgrade before starting build
$apt_update = 1;
$apt_upgrade = 1;
# build everything including source for source-only uploads
$build_arch_all = 1;
$build_arch_any = 1;
$build_source = 1;
$source_only_changes = 1;
# go to shell on failure instead of exiting
$external_commands =   "build-failed-commands" => [ [ '%SBUILD_SHELL' ] ]  ;
# always clean build dir, even on failure
$purge_build_directory = "always";
# run lintian
$run_lintian = 1;
$lintian_opts = [ '-i', '-I', '-E', '--pedantic' ];
# do not run piuparts
$run_piuparts = 0;
# run autopkgtest
$run_autopkgtest = 1;
$autopkgtest_root_args = '';
$autopkgtest_opts = [ '--apt-upgrade', '--', 'unshare', '--release', '%r', '--arch', '%a', '--prefix=/dev/shm/tmp.autopkgtest.' ];
# set uploader for correct signing
$uploader_name = 'Stephan Lachnit <>';
You should adjust uploader_name. If you don t want to run autopkgtest or lintian by default you can also disable it here. Note that for packages that need a lot of space for building, you might want to comment the unshare_tmpdir_template line to prevent a OOM build failure. You can now build your Debian packages with the sbuild command :)

Finishing touches You can add these variables to your ~/.bashrc as bonus (with adjusted name / email):
export DEBFULLNAME="<your_name>"
export DEBEMAIL="<your_email>"
export DEB_BUILD_OPTIONS="parallel=<threads>"
In particular adjust the value of parallel to ensure parallel builds. If you are new to signing / uploading your package, first install the required tools:
sudo apt install devscripts dput-ng
Create ~/.devscripts and insert:
You can now sign the .changes file with:
debsign ../<pkgname_version_arch>.changes
And for source-only uploads with:
debsign -S ../<pkgname_version_arch>_source.changes
If you don t introduce a new binary package, you always want to go with source-only changes. You can now upload the package to Debian with
dput ../<filename>.changes

Update Feburary 22nd Jochen Sprickerhof, who originally advised me to use the unshare backend, commented that one can also use --include=auto-apt-proxy instead of the --aptopt option in mmdebstrap to detect apt proxies automatically. He also let me know that it is possible to use autopkgtest on tmpfs (config in the blog post is updated) and added an entry on the sbuild wiki page on how to setup sbuild+unshare with ccache if you often need to build a large package. Further, using --variant=apt and --include=build-essential will produce smaller build chroots if wished. On the contrary, one can of course also use the --include option to include debhelper and lintian (or any other packages you like) to further decrease the setup time. However, staying with buildd variant is a good choice for official uploads.

Resources for further reading
Thanks for reading!

7 February 2023

Stephan Lachnit: Installing Debian on F2FS rootfs with deboostrap and systemd-boot

I recently got a new NVME drive. My plan was to create a fresh Debian install on an F2FS root partition with compression for maximum performance. As it turns out, this is not entirely trivil to accomplish. For one, the Debian installer does not support F2FS (here is my attempt to add it from 2021). And even if it did, grub does not support F2FS with the extra_attr flag that is required for compression support (at least as of grub 2.06). Luckily, we can install Debian anyway with all these these shiny new features when we go the manual road with debootstrap and using systemd-boot as bootloader. We can break down the process into several steps:
  1. Creating the partition table
  2. Creating and mounting the root partition
  3. Bootstrapping with debootstrap
  4. Chrooting into the system
  5. Configure the base system
  6. Define static file system information
  7. Installing the kernel and bootloader
  8. Finishing touches
Warning: Playing around with partitions can easily result in data if you mess up! Make sure to double check your commands and create a data backup if you don t feel confident about the process.

Creating the partition partble The first step is to create the GPT partition table on the new drive. There are several tools to do this, I recommend the ArchWiki page on this topic for details. For simplicity I just went with the GParted since it has an easy GUI, but feel free to use any other tool. The layout should look like this:
Type         Partition        Suggested size
EFI          /dev/nvme0n1p1           512MiB
Linux swap   /dev/nvme0n1p2             1GiB
Linux fs     /dev/nvme0n1p3        remainder
  • The disk names are just an example and have to be adjusted for your system.
  • Don t set disk labels, they don t appear on the new install anyway and some UEFIs might not like it on your boot partition.
  • The size of the EFI partition can be smaller, in practive it s unlikely that you need more than 300 MiB. However some UEFIs might be buggy and if you ever want to install an additional kernel or something like memtest86+ you will be happy to have the extra space.
  • The swap partition can be omitted, it is not strictly needed. If you need more swap for some reason you can also add more using a swap file later (see ArchWiki page). If you know you want to use suspend-to-RAM, you want to increase the size to something more than the size of your memory.
  • If you used GParted, create the EFI partition as FAT32 and set the esp flag. For the root partition use ext4 or F2FS if available.

Creating and mounting the root partition To create the root partition, we need to install the f2fs-tools first:
sudo apt install f2fs-tools
Now we can create the file system with the correct flags:
mkfs.f2fs -O extra_attr,inode_checksum,sb_checksum,compression,encrypt /dev/nvme0n1p3
For details on the flags visit the ArchWiki page. Next, we need to mount the partition with the correct flags. First, create a working directory:
mkdir boostrap
cd boostrap
mkdir root
export DFS=$(pwd)/root
Then we can mount the partition:
sudo mount -o compress_algorithm=zstd:6,compress_chksum,atgc,gc_merge,lazytime /dev/nvme0n1p3 $DFS
Again, for details on the mount options visit the above mentioned ArchWiki page.

Bootstrapping with debootstrap First we need to install the debootstrap package:
sudo apt install debootstrap
Now we can do the bootstrapping:
debootstrap --arch=amd64 --components=main,contrib,non-free,non-free-firmware unstable $DFS
  • --arch sets the CPU architecture (see Debian Wiki).
  • --components sets the archive components, if you don t want non-free pacakges you might want to remove some entries here.
  • unstable is the Debian release, you might want to change that to testing or bookworm.
  • $DFS points to the mounting point of the root partition.
  • is the Debian mirror, you might want to set that to or similar if you have a fast mirror in you area.

Chrooting into the system Before we can chroot into the newly created system, we need to prepare and mount virtual kernel file systems. First create the directories:
sudo mkdir -p $DFS/dev $DFS/dev/pts $DFS/proc $DFS/sys $DFS/run $DFS/sys/firmware/efi/efivars $DFS/boot/efi
Then bind-mount the directories from your system to the mount point of the new system:
sudo mount -v -B /dev $DFS/dev
sudo mount -v -B /dev/pts $DFS/dev/pts
sudo mount -v -B /proc $DFS/proc
sudo mount -v -B /sys $DFS/sys
sudo mount -v -B /run $DFS/run
sudo mount -v -B /sys/firmware/efi/efivars $DFS/sys/firmware/efi/efivars
As a last step, we need to mount the EFI partition:
sudo mount -v -B /dev/nvme0n1p1 $DFS/boot/efi
Now we can chroot into new system:
sudo chroot $DFS /bin/bash

Configure the base system The first step in the chroot is setting the locales. We need this since we might leak the locales from our base system into the chroot and if this happens we get a lot of annoying warnings.
export LC_ALL=C.UTF-8 LANG=C.UTF-8
apt install locales console-setup
Set your locales:
dpkg-reconfigure locales
Set your keyboard layout:
dpkg-reconfigure keyboard-configuration
Set your timezone:
dpkg-reconfigure tzdata
Now you have a fully functional Debian chroot! However, it is not bootable yet, so let s fix that.

Define static file system information The first step is to make sure the system mounts all partitions on startup with the correct mount flags. This is done in /etc/fstab (see ArchWiki page). Open the file and change its content to:
# file system                               mount point   type   options                                                            dump   pass
# NVME efi partition
UUID=XXXX-XXXX                              /boot/efi     vfat   umask=0077                                                         0      0
# NVME swap
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX   none          swap   sw                                                                 0      0
# NVME main partition
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX   /             f2fs   compress_algorithm=zstd:6,compress_chksum,atgc,gc_merge,lazytime   0      1
You need to fill in the UUIDs for the partitions. You can use
ls -lAph /dev/disk/by-uuid/
to match the UUIDs to the more readable disk name under /dev.

Installing the kernel and bootloader First install the systemd-boot and efibootmgr packages:
apt install systemd-boot efibootmgr
Now we can install the bootloader:
bootctl install --path=/boot/efi
You can verify the procedure worked with
efibootmgr -v
The next step is to install the kernel, you can find a fitting image with:
apt search linux-image-*
In my case:
apt install linux-image-amd64
After the installation of the kernel, apt will add an entry for systemd-boot automatically. Neat! However, since we are in a chroot the current settings are not bootable. The first reason is the boot partition, which will likely be the one from your current system. To change that, navigate to /boot/efi/loader/entries, it should contain one config file. When you open this file, it should look something like this:
title      Debian GNU/Linux bookworm/sid
version    6.1.0-3-amd64
machine-id 2967cafb6420ce7a2b99030163e2ee6a
sort-key   debian
options    root=PARTUUID=f81d4fae-7dec-11d0-a765-00a0c91e6bf6 ro systemd.machine_id=2967cafb6420ce7a2b99030163e2ee6a
linux      /2967cafb6420ce7a2b99030163e2ee6a/6.1.0-3-amd64/linux
initrd     /2967cafb6420ce7a2b99030163e2ee6a/6.1.0-3-amd64/initrd.img-6.1.0-3-amd64
The PARTUUID needs to point to the partition equivalent to /dev/nvme0n1p3 on your system. You can use
ls -lAph /dev/disk/by-partuuid/
to match the PARTUUIDs to the more readable disk name under /dev. The second problem is the ro flag in options which tell the kernel to boot in read-only mode. The default is rw, so you can just remove the ro flag. Once this is fixed, the new system should be bootable. You can change the boot order with:
efibootmgr --bootorder
However, before we reboot we might add well add a user and install some basic software.

Finishing touches Add a user:
useradd -m -G sudo -s /usr/bin/bash -c 'Full Name' username
Debian provides a TUI to install Desktop Environment. To open it, run:
Now you can finally reboot into your new system:

Resources for further reading
Thanks for reading!

13 May 2021

Bits from Debian: New Debian Developers and Maintainers (March and April 2021)

The following contributors got their Debian Developer accounts in the last two months: The following contributors were added as Debian Maintainers in the last two months: Congratulations!

16 November 2020

Bits from Debian: New Debian Developers and Maintainers (September and October 2020)

The following contributors got their Debian Developer accounts in the last two months: The following contributors were added as Debian Maintainers in the last two months: Congratulations!

11 August 2020

Jonathan Carter: GameMode in Debian

What is GameMode, what does it do? About two years ago, I ran into some bugs running a game on Debian, so installed Windows 10 on a spare computer and ran it on there. I learned that when you launch a game in Windows 10, it automatically disables notifications, screensaver, reduces power saving measures and gives the game maximum priority. I thought Oh, that s actually quite nice, but we probably won t see that kind of integration on Linux any time soon . The very next week, I read the initial announcement of GameMode, a tool from Feral Interactive that does a bunch of tricks to maximise performance for games running on Linux. When GameMode is invoked it:

How GameMode is invoked Some newer games (proprietary games like Rise of the Tomb Raider , Total War Saga: Thrones of Britannia , Total War: WARHAMMER II , DiRT 4 and Total War: Three Kingdoms ) will automatically invoke GameMode if it s installed. For games that don t, you can manually evoke it using the gamemoderun command. Lutris is a tool that makes it easy to install and run games on Linux, and it also integrates with GameMode. (Lutris is currently being packaged for Debian, hopefully it will make it in on time for Bullseye).

Screenshot of Lutris, a tool that makes it easy to install your non-Linux games, which also integrates with GameMode.

GameMode in Debian The latest GameMode is packaged in Debian (Stephan Lachnit and I maintain it in the Debian Games Team) and it s also available for Debian 10 (Buster) via buster-backports. All you need to do to get up and running with GameMode is to install the gamemode package. GameMode in Debian supports 64 bit and 32 bit mode, so running it with older games (and many proprietary games) still work. Some distributions (like Arch Linux), have dropped 32 bit support, so 32 bit games on such systems lose any kind of integration with GameMode even if you can get those games running via other wrappers on such systems. We also include a binary called gamemode-simulate-game (installed under /usr/games/). This is a minimalistic program that will invoke gamemode automatically for 10 seconds and then exit without an error if it was successful. Its source code might be useful if you d like to add GameMode support to your game, or patch a game in Debian to automatically invoke it. In Debian we install Gamemode s example config file to /etc/gamemode.ini where a user can customise their system-wide preferences, or alternatively they can place a copy of that in ~/.gamemode.ini with their personal preferences. In this config file, you can also choose to explicitly allow or deny games. GameMode might also be useful for many pieces of software that aren t games. I haven t done any benchmarks on such software yet, but it might be great for users who use CAD programs or use a combination of their CPU/GPU to crunch a large amount of data. I ve also packaged an extension for GNOME called gamemode-extension. The Debian package is called gnome-shell-extension-gamemode . You ll need to enable it using gnome-tweaks after installation, it will then display a green controller in your notification area whenever GameMode is active. It s only in testing/bullseye since it relies on a newer gnome-shell than what s available in buster.

Running gamemode-simulate-game, with the shell extension showing that it s activated in the top left corner.