Differences between revisions 15 and 16
Revision 15 as of 2021-04-08 17:36:33
Size: 13741
Editor: ?RolandClobus
Comment: The file from note 6 is no longer in the image. Added KDE
Revision 16 as of 2021-06-15 08:55:11
Size: 13927
Editor: ?RolandClobus
Comment: Update the command line for reprotest
Deletions are marked like this. Additions are marked like this.
Line 301: Line 301:
# This is probably better, but bails at the moment
# reprotest --store-dir store --variations=+all,-user_group --diffoscope-arg="--html-dir=html_{0}" "lb clean --purge&&lb config&&lb build" "*.iso"
reprotest --store-dir store --variations=-user_group --diffoscope-arg="--html-dir=html_{0}" "lb clean --purge&&lb config&&lb build" "*.iso"
}}}

Note: this command line is not correct yet, but shows the basic idea.
reprotest --variations=-all,+environment,+build_path,-kernel,+aslr,+num_cpus,+time,-user_group,-fileordering,-domain_host,+home,+locales,+exec_path,+timezone,-umask "lb clean --purge&&lb config&&lb build" "*.iso"
# Disabled tests:
# kernel The variant with kernel 2.6 is too old for debootstrap
# user_group Live build only works for root, the variation needs a list
# fileordering Disorderfs needs to be mounted with dev,exec,suid
# domain_host Needs additional rights during debootstrap
# umask Some files get a different umask, further investigation is required
}}}


Reproducible Live images

This page tracks the progress on creating reproducible live images, using live-build from DebianLive

Configuration

The computer that is used for generating live images:

  • Debian/sid
  • apt-cacher-ng running on http://localhost:3142

  • The most recent checkout of the git repository of live-build (https://salsa.debian.org/live-team/live-build)

  • An additional line in /etc/apt-cacher-ng/acnf.conf: VfilePatternEx: /project/trace/ftp-master\.debian\.org$

Snapshot

In order to get a more reproducible image, a snapshot is used. At the time of focusing on Bullseye, the timestamp 20210101T083123Z (1609489883) was chosen.

Considerations

  • Building an image must be fast, because a lot of rebuilds will be required -> use /dev/shm

  • Reduce network traffic, don't download the same files over-and-over -> use apt-cacher-ng

  • While looking for (non-)reproducibility, the command line option --parent-mirror-binary is used. Official live images should not use this command line option (and will therefore use deb.debian.org in /var/lib/apt/lists)

Preparing the build environment

All command lines must be executed as root.

export LIVE_BUILD=/home/roland/git/live-build
export SOURCE_DATE_EPOCH=1609489883
cd /dev/shm
mount /dev/shm -odev,exec,remount
mkdir live
cd live

Building images for Debian Buster

Timestamp: 20210210T031935Z

export LIVE_BUILD=/home/roland/git/live-build
export SOURCE_DATE_EPOCH=1612927175
cd /dev/shm
mount /dev/shm -odev,exec,remount
mkdir live
cd live

Mini, with live installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210210T031935Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/202102101031935Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution buster --debian-installer live --cache-packages false

Building images for Debian Bullseye

Image

Installer

Reproducible

Notes

mini

none

yes

mini

live/text

yes

1

mini

live/gui

yes

1

mini

daily

yes

2

standard

none

yes

3, 4

standard

live

yes

1, 3, 4

GNOME

none

yes

3, 4, 5

GNOME

live

yes

1, 3, 4, 5

KDE

live

yes

1, 3, 4, 5

  • Note 1: The installer fails, because the installer uses an older kernel. Use the daily installer instead, until the installer is updated
  • Note 2: Reproducibility tested by setting SOURCE_DATE_EPOCH during the first lb build and running the second build a few minutes after finishing the first build

  • Note 3: fontconfig uses random GUIDs, which can be circumvented. Hooks 1000 and 1001 implement a work around
  • Note 4: mdadm adds a timestamp to the configuration file, which can be circumvented. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982607. Until mdadm is updated, hook 1002 implements a work around

  • Note 5: During update-initramfs, the hook of plymouth adds fonts to the initrds. Hooks 1000 and 1003 implement a work around

Command lines

Mini, without installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210101T083123Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution bullseye --debian-installer none --cache-packages false

Mini, with live/text-only installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210101T083123Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution bullseye --debian-installer live --cache-packages false --debian-installer-gui false

Mini, with latest installer

unset SOURCE_DATE_EPOCH
lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/deb.debian.org/debian --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --distribution bullseye --debian-installer live --cache-packages false --debian-installer-gui false --parent-debian-installer-distribution daily
# When doing comparisons, use the following line for the first run:
#   export SOURCE_DATE_EPOCH=`date +%s`; lb build

Mini, with live installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210101T083123Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution bullseye --debian-installer live --cache-packages false

Standard, without installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210101T083123Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution bullseye --debian-installer none --cache-packages false
echo "live-task-standard" > config/package-lists/desktop.list.chroot

Standard, with live installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210101T083123Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution bullseye --debian-installer live --cache-packages false
echo "live-task-standard" > config/package-lists/desktop.list.chroot

GNOME desktop, without installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210101T083123Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution bullseye --debian-installer none --cache-packages false
echo "live-task-gnome" > config/package-lists/desktop.list.chroot

GNOME desktop, with live installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210101T083123Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution bullseye --debian-installer live --cache-packages false
echo "live-task-gnome" > config/package-lists/desktop.list.chroot

KDE desktop, with live installer

lb config --apt-http-proxy http://localhost:3142 --parent-mirror-bootstrap http://localhost:3142/snapshot.debian.org/archive/debian/20210101T083123Z --parent-mirror-binary http://snapshot.debian.org/archive/debian/20210101T083123Z --security false --updates false --apt-options "--yes -o Acquire::Check-Valid-Until=false" --distribution bullseye --debian-installer live --cache-packages false
echo "live-task-kde" > config/package-lists/desktop.list.chroot

The hook scripts that should be applied after any of the command lines above, to fix non-reproducible packages

cat > config/hooks/normal/1000-reproducible-function-uuid_generate_random.hook.chroot << EOF
#!/bin/sh
set -e

# util-linux creates random UUIDs when uuid_generate_random is called
# Use LD_PRELOAD to replace uuid_generate_random with a less random version

# Don't run if gcc is not installed
if [ ! -e /usr/bin/cc ];
then
  exit 0
fi

cat > unrandomize_uuid_generate_random.c << END_OF_SOURCE
#include <stdlib.h>
#include <stdio.h>

#define SEQUENCE_FILENAME "/var/cache/unrandomize_uuid_generate_random.sequence_number"

/* https://tools.ietf.org/html/rfc4122 */
typedef unsigned char uuid_t[16];

/* Our pseudo-random version */
void uuid_generate_random(uuid_t out)
{
  /* Nil UUID */
  for (int i=0;i<16;i++) {
    out[i] = 0x00;
  }
  out[6]=0x40; /* UUID version 4 means randomly generated */
  out[8]=0x80; /* bit7=1,bit6=0 */

  /* The file doesn't need to exist yet */
  FILE *f = fopen(SEQUENCE_FILENAME, "rb");
  if (f) {
    fread(out+12, 4, 1, f);
    fclose(f);
  }
  /* Use the next number. Endianness is not important */
  (*(unsigned long*)(out+12))++;

  unsigned long long epoch;
  /* Use SOURCE_DATE_EPOCH when provided */
  char *date = getenv("SOURCE_DATE_EPOCH");
  if (date) {
    epoch = strtoll(date, NULL, 10);
  } else {
    epoch = 0ll;
  }
  out[0] = (epoch & 0xFF000000) >> 24;
  out[1] = (epoch & 0x00FF0000) >> 16;
  out[2] = (epoch & 0x0000FF00) >>  8;
  out[3] = (epoch & 0x000000FF);

  /* Write the sequence number */
  f = fopen(SEQUENCE_FILENAME, "wb");
  if (f) {
    fwrite(out+12, 4, 1, f);
    fclose(f);
  }
}
END_OF_SOURCE
/usr/bin/cc -shared -fPIC unrandomize_uuid_generate_random.c -Wall --pedantic -o /usr/lib/unrandomize_uuid_generate_random.so
rm -f unrandomize_uuid_generate_random.c
EOF
cat > config/hooks/normal/1001-reproducible-fontconfig.hook.chroot << EOF
#!/bin/sh
set -e

# fontconfig creates non-reproducible files with UUIDs
# See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=864082
#
# Because the UUIDs should not be deleted, the proposed work-around is:
# * Use LD_PRELOAD to replace uuid_generate_random with a less random version

# Don't run if fontconfig is not installed
if [ ! -e /usr/bin/fc-cache ];
then
  exit 0
fi

# Don't run if the LD_PRELOAD module is not compiled
if [ ! -e /usr/lib/unrandomize_uuid_generate_random.so ];
then
  exit 0
fi

LD_PRELOAD=/usr/lib/unrandomize_uuid_generate_random.so /usr/bin/fc-cache --force --really-force --system-only --verbose
EOF
cat > config/hooks/normal/1002-reproducible-mdadm.hook.chroot << EOF
#!/bin/sh
set -e

# mkconf of mdadm creates a file with a timestamp
# A bug report with patch is available at https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982607
# This script duplicates that patch

# Don't run if mdadm is not installed
if [ ! -e /usr/share/mdadm/mkconf ];
then
  exit 0
fi

# If mkconf already contains references to SOURCE_DATE_EPOCH, there is no need to patch the file
if grep -q SOURCE_DATE_EPOCH /usr/share/mdadm/mkconf;
then
  exit 0
fi
sed -i -e '/# This configuration was auto-generated on/cif [ -z \$SOURCE_DATE_EPOCH ]; then\n  echo "# This configuration was auto-generated on \$(date -R) by mkconf"\nelse\n  echo "# This configuration was auto-generated on \$(date -R --utc -d@\$SOURCE_DATE_EPOCH) by mkconf"\nfi' /usr/share/mdadm/mkconf
EOF
cat > config/hooks/normal/1003-reproducible-plymouth.hook.chroot << EOF
#!/bin/sh
set -e

# The hook of plymouth in update-initramfs calls fc-cache

# Don't run if plymouth is not installed
if [ ! -e /usr/share/initramfs-tools/hooks/plymouth ];
then
  exit 0
fi

# Don't patch if the LD_PRELOAD module is not compiled
if [ ! -e /usr/lib/unrandomize_uuid_generate_random.so ];
then
  exit 0
fi

# If the hook already contains references to LD_PRELOAD, there is no need to patch the file
if grep -q LD_PRELOAD /usr/share/initramfs-tools/hooks/plymouth;
then
  exit 0
fi
sed -i -e 's|fc-cache -s|LD_PRELOAD=/usr/lib/unrandomize_uuid_generate_random.so fc-cache|' /usr/share/initramfs-tools/hooks/plymouth
EOF

Checking reproducibility

Ideally reprotest will be used to check reproducibility. For now, 2 images are built and then compared with diffoscope.

Using diffoscope

# 1) Prepare the build environment
# 2) Run the command line to create the configuration (see above)
lb build
mv live-image-amd64.hybrid.iso run01.iso
lb clean --purge
lb config
lb build
mv live-image-amd64.hybrid.iso run02.iso
diffoscope run01.iso run02.iso --html-dir html_run01_02

Using reprotest

reprotest requires full access on /tmp, so it must be remounted (when applicable)

# 1) Prepare the build environment
# 2) Run the command line to create the configuration (see above)
mount /tmp -odev,exec,suid,remount
reprotest  --variations=-all,+environment,+build_path,-kernel,+aslr,+num_cpus,+time,-user_group,-fileordering,-domain_host,+home,+locales,+exec_path,+timezone,-umask  "lb clean --purge&&lb config&&lb build" "*.iso"
# Disabled tests:
#  kernel        The variant with kernel 2.6 is too old for debootstrap
#  user_group    Live build only works for root, the variation needs a list
#  fileordering  Disorderfs needs to be mounted with dev,exec,suid
#  domain_host   Needs additional rights during debootstrap
#  umask         Some files get a different umask, further investigation is required

See also

Page maintainer: Roland Clobus