Upgrading GNU/Linux from 32 bit to 64 bit HowTo

1. Introduction

This brief HOWTO shows how to take a working 32 bit 12.04 installation and convert it into a 64 bit system. You will be able to keep all your programs, settings and data. You start with a 32 bit system that can run 64 bit programs, then convert it to a 64 bit system that can run 32 bit programs.

With the upcoming release of Debian GNU/Linux wheezy, a new feature called multiarch is being introduced. The facility permits the installation of executable files (such as libraries and programs) from multiple architectures simultaneously on the same system. The primary use of this is to allow 32 bit programs to be run on a 64 bit system, but it has other uses.

With the release of Ubuntu LTS 12.04 (Precise Pangolin), this feature is available now.

Update 2014-06-24: This HowTo has been replaced for the new 14.04 LTS release of Ubuntu. The process is now more straight-forward.

2. Boot into 64 bit

The 32 bit kernel does not allow the execution of 64 bit programs. However the 64 bit kernel allows the execution of both 32 bit and 64 bit programs, so this is the first thing needed. Run the following in turn to allow 64 bit programs to be installed as a foreign architecture, then install the 64 bit kernel. We also install debootstrap as we will use it later.

echo "foreign-architecture amd64" >/etc/dpkg/dpkg.cfg.d/multiarch
apt-get update
apt-get install linux-image-3.2.0-23-generic:amd64 debootstrap

You may also wish to deinstall all the old 32 bit kernels at this point. Now reboot with the newly installed 64 bit amd64 kernel before continuing.

3. Pre-prepare files

Save a checkpoint of the packages we have installed at the start. The aim is to have the same packages installed at the end, just in the 64 bit architecture.

dpkg --get-selections "*:i386"|grep -v deinstall >dpkg-get-selections.cp0.i386
dpkg --get-selections "*:amd64"|grep -v deinstall >dpkg-get-selections.cp0.amd64
dpkg --get-selections "*:all"|grep -v deinstall >dpkg-get-selections.cp0.all

Download some essential files that we will call upon later. Unpack dpkg and dash as we will need the executables to be available later.

mkdir -p archives/partial
rm archives/*.deb
apt-get install -d -o Dir::Cache::Archives=./archives apt:amd64 dpkg:amd64 bash:amd64 dash:amd64
rm -Rf files/*
dpkg-deb -x archives/dpkg_*.deb files
dpkg-deb -x archives/dash_*.deb files

Also create a list of, and download, the packages for the base system. We can get away with including ssh in the base system, but most additional packages will break the migration process.

mkdir -p bootstrap
rm -R bootstrap/*
debootstrap --arch=amd64 --download-only --include=openssh-client,openssh-server precise ./bootstrap
ls -1 bootstrap/var/cache/apt/archives/|egrep "\.deb$"|cut -d "_" -f1|awk '{print $1 " install"}' >dpkg-get-selections.base

4. Backups

4.1. PostgreSQL

The controlfile format for PostgreSQL differs on different architectures. Therefore we need to create an architecture-independent backup that can be restored after the migration.

su - postgres -c "umask 77; pg_dumpall >/tmp/pg_dumpall_9_1.sql"
mv /tmp/pg_dumpall_9_1.sql .
bzip2 -f pg_dumpall_9_1.sql
mkdir -p etc/postgresql/9.1/main
cp -pi /etc/postgresql/9.1/main/pg_hba.conf etc/postgresql/9.1/main
apt-get purge postgresql-9.1

5. 32 bit base system

Shrink down the current selection of installed packages on the current 32 bit system to the base system of essential packages only.

dpkg --clear-selections
dpkg --set-selections <dpkg-get-selections.base
apt-get dselect-upgrade

6. Upgrade base system

Install some miscellaneous packages and all the libraries that we will need immediately for our base system upgrade.

apt-get install --no-install-recommends linux-image-3.2.0-23-generic:amd64
apt-get remove ubuntu-minimal
apt-get install gcc-4.6-base:amd64 libc6:amd64 libgcc1:amd64 libssl1.0.0:amd64
dpkg -i archives/lib*.deb archives/zlib*.deb

Start with the installation of 64 bit versions of dpkg and apt. We unpacked apt earlier, so we can use the unpacked version to install the replacement package.

rm /etc/dpkg/dpkg.cfg.d/multiarch
dpkg --force-remove-essential --force-depends -r dpkg:i386
PATH=$PATH:files/usr/bin:files/sbin dpkg -i archives/dpkg_*_amd64.deb
dpkg -r apt:i386
dpkg -i archives/apt_*

Fix the apt dependencies.

apt-get update
apt-get -f install

The installation will halt with the following error. This is because both dash and bash were removed together.

dpkg: error processing dash:i386 (--remove):
 subprocess installed post-removal script returned error exit status 2

Install our unpacked version of dash to resolve the missing dependency.

cp -pi files/bin/dash /bin/sh
apt-get -f install

The next message concerns a python-minimal dependency problem.

dpkg: dependency problems prevent configuration of python-minimal:
 python-minimal depends on python2.7-minimal (>= 2.7.3); however:
  Package python2.7-minimal is not configured yet.

This dependency is simple to resolve. Now continue resolving dependencies that apt cannot automatically resolve.

dpkg -i /var/cache/apt/archives/python-minimal_*_amd64.deb /var/cache/apt/archives/python2.7-minimal_*_amd64.deb
apt-get -f install
dpkg --configure -a
apt-get autoremove

Now install the 64 bit shells. I answer "Yes" to the debconf prompt when configuring dash as the system shell.

cp -pi files/bin/dash /bin/bash
apt-get install dash
dpkg --configure -a
apt-get install bash
dpkg --configure -a

Save another checkpoint to document the state of the architecture migration.

dpkg --get-selections "*:i386"|grep -v deinstall >dpkg-get-selections.cp1.i386
dpkg --get-selections "*:amd64"|grep -v deinstall >dpkg-get-selections.cp1.amd64
dpkg --get-selections "*:all"|grep -v deinstall >dpkg-get-selections.cp1.all

Gradually replace each 32 bit package with its 64 bit equivalent.

apt-get install apt-utils
apt-get install --reinstall locales
#dpkg --get-selections "*:i386"|grep -v deinstall|grep -v ^lib|cut -d: -f1

apt-get install --no-install-recommends sudo bsdutils bzip2 crda logrotate diffutils e2fslibs file gnupg gpgv grep gzip hostname ifupdown iproute iputils-ping isc-dhcp-client initscripts
apt-get install login mawk
apt-get --no-install-recommends install mount mountall
apt-get install module-init-tools multiarch-support ncurses-bin
apt-get --no-install-recommends install net-tools netcat-openbsd passwd ureadahead base-passwd
apt-get install --no-install-recommends vim-common vim-tiny whiptail xz-utils
dpkg --configure -a
apt-get install util-linux
apt-get install udev
apt-get install procps e2fsprogs
dpkg --configure -a
apt-get install sysvinit-utils upstart
dpkg --configure -a

apt-get remove e2fslibs:i386 zlib1g:i386
apt-get --no-install-recommends install openssh-server openssh-client
dpkg --configure -a

We are now down to the last few 32 bit packages, but these are essential and their removal/replacement will break the base system. Thus we manually unpack them now so we can continue to access their programs while they are being replaced.

dpkg-deb -x bootstrap/var/cache/apt/archives/tar_*.deb files
dpkg --force-remove-essential --force-depends -r tar:i386
cp -pi files/bin/tar /bin
dpkg -i bootstrap/var/cache/apt/archives/tar_*.deb

dpkg-deb -x bootstrap/var/cache/apt/archives/findutils_*.deb files
dpkg --force-depends -r initramfs-tools
dpkg --force-remove-essential -r findutils:i386
PATH=$PATH:files/usr/bin dpkg -i bootstrap/var/cache/apt/archives/findutils_*.deb
apt-get install initramfs-tools

dpkg-deb -x bootstrap/var/cache/apt/archives/coreutils_*.deb files
dpkg --force-remove-essential --force-depends -r coreutils:i386
PATH=$PATH:files/bin dpkg -i bootstrap/var/cache/apt/archives/coreutils_*.deb

apt-get install libpam-modules-bin
apt-get remove gcc-4.6-base:i386

The libc6-bin package needs a little nudge to install. When the following message appears, run the commands to resume the package configuration.

dpkg-deb -x bootstrap/var/cache/apt/archives/libc-bin_*.deb files
apt-get install libc-bin

dpkg: warning: 'ldconfig' not found in PATH or not executable.
dpkg: error: 1 expected program not found in PATH or not executable.

cp -pi files/sbin/ldconfig files/sbin/ldconfig.real /sbin
apt-get install libc-bin
dpkg --configure -a

Take another look at the packages we have installed. There should not be any i386 architecture packages installed at this point. The base system now comprises entirely amd64 and all packages.

dpkg --get-selections "*:i386"|grep -v deinstall >dpkg-get-selections.cp2.i386
dpkg --get-selections "*:amd64"|grep -v deinstall >dpkg-get-selections.cp2.amd64
dpkg --get-selections "*:all"|grep -v deinstall >dpkg-get-selections.cp2.all

7. Re-install packages

Now that the base system has been migrated to 64 bit, we can begin the process of re-installing the packages that were previously installed as 32 bit software. It may be necessary to run the installs and configures multiple times until all dependencies are met. Start with the most important software and any standard meta-packages.

apt-get install rsync
dpkg --configure -a

apt-get install ubuntu-desktop ubuntu-minimal ubuntu-standard
dpkg --configure -a
apt-get install ubuntu-desktop ubuntu-minimal ubuntu-standard
dpkg --configure -a

I use the Gnome desktop environment, so I will install the packages now. When asked to choose a display manager I choose "Okay" then "lightdm".

apt-get install gnome-shell gnome-desktop-environment
dpkg --configure -a

Now we are ready to install all the software packages that were previously installed.

cat dpkg-get-selections.cp0.i386 dpkg-get-selections.cp0.all|grep -v deinstall|awk '{print $1 ":amd64 install"}'|dpkg --set-selections
rm /etc/dpkg/dpkg.cfg.d/multiarch

apt-get update
apt-get dselect-upgrade
dpkg --configure -a
apt-get dselect-upgrade
dpkg --configure -a

I saw the following message when running through these steps. I do not know if it is harmful or related to the later message about an invalid debconf value.

Use of uninitialized value $_[0] in join or string at /usr/share/perl5/Debconf/Client/ConfModule.pm line 121, <STDIN> line 30.

Continue with the installation. You will then see another message.

apt-get dselect-upgrade

Package configuration

                        dictionaries-common: wordlists

   An invalid debconf value [] has been found
 
   It does not correspond to any installed package in the system.
 
   That is usually caused by problems at some time during packages
   installation, where the package providing [] was selected for
   installation but finally not installed because of errors in other
   packages.
 
   To fix this error, reinstall (or install) the package that provides the
   missing value.  Then, if you don't want this package on your system,
   remove it, which will also remove its debconf entries. Menu to be shown
   after this message will try to leave the system in a working state until
   then.
 
                                    <Ok>

Now complete the package installation.

dpkg --configure -a

8. Restore backups

8.1. PostgreSQL

The postgresql package was re-installed for us. Its configuration and data needs to be restored.

cp -p etc/postgresql/9.1/main/pg_hba.conf /etc/postgresql/9.1/main
/etc/init.d/postgresql reload
bzcat pg_dumpall_9_1.sql.bz2 >/tmp/pg_dumpall_9_1.sql
su - postgres -c "cd /tmp; psql <pg_dumpall_9_1.sql >psql.out 2>psql.err"
mv -i /tmp/psql.* .
rm /tmp/pg_dumpall_9_1.sql

9. Allow 32 bit packages

We can now re-enable the installation of 32 bit packages. In other words we have a multiarch system that runs 64 bit but allows the installation of 32 bit programs and libraries.

cp -pi files/etc/dpkg/dpkg.cfg.d/multiarch /etc/dpkg/dpkg.cfg.d
apt-get update
apt-get dselect-upgrade

Take one final look at what packages are now installed.

dpkg --get-selections "*:i386"|grep -v deinstall >dpkg-get-selections.cp3.i386
dpkg --get-selections "*:amd64"|grep -v deinstall >dpkg-get-selections.cp3.amd64
dpkg --get-selections "*:all"|grep -v deinstall >dpkg-get-selections.cp3.all

10. Re-install 32 bit-only programs

Re-install any packages that are 32 bit only, for example:

apt-get install googleearth

Notes

There are some packages that pre-depend on bash, but are not documented as such in their control files. I need to raise a bug for these: libssl1.0.0, kismet and grub-pc.

See also

• Upgrade Debian from 32 bit to 64 bit
• Debian multiarch wiki
• Debian policy manual, dependencies