Table of Contents
We suggest that before upgrading you also read the information in Chapter 5, Issues to be aware of for bullseye. That chapter covers potential issues which are not directly related to the upgrade process but could still be important to know about before you begin.
Before upgrading your system, it is strongly recommended that you make a full backup, or at least back up any data or configuration information you can't afford to lose. The upgrade tools and process are quite reliable, but a hardware failure in the middle of an upgrade could result in a severely damaged system.
The main things you'll want to back up are the contents of
/etc
, /var/lib/dpkg
,
/var/lib/apt/extended_states
and the output of
dpkg --get-selections "*"
(the quotes are important). If
you use aptitude to manage packages on your system, you
will also want to back up /var/lib/aptitude/pkgstates
.
The upgrade process itself does not modify anything in the
/home
directory. However, some applications (e.g. parts
of the Mozilla suite, and the GNOME and KDE desktop environments) are known to
overwrite existing user settings with new defaults when a new version of the
application is first started by a user. As a precaution, you may want to make
a backup of the hidden files and directories (“dotfiles”) in users' home
directories. This backup may help to restore or recreate the old settings.
You may also want to inform users about this.
Any package installation operation must be run with superuser privileges, so
either log in as root
or use su or sudo to
gain the necessary access rights.
The upgrade has a few preconditions; you should check them before actually executing the upgrade.
It's wise to inform all users in advance of any upgrades you're planning, although users accessing your system via an ssh connection should notice little during the upgrade, and should be able to continue working.
If you wish to take extra precautions, back up or unmount the
/home
partition before upgrading.
You will have to do a kernel upgrade when upgrading to bullseye, so a reboot will be necessary. Typically, this will be done after the upgrade is finished.
There might be services that are offered by the system which are associated with packages that will be included in the upgrade. If this is the case, please note that, during the upgrade, these services will be stopped while their associated packages are being replaced and configured. During this time, these services will not be available.
The precise downtime for these services will vary depending on the number of packages being upgraded in the system, and it also includes the time the system administrator spends answering any configuration questions from package upgrades. Notice that if the upgrade process is left unattended and the system requests input during the upgrade there is a high possibility of services being unavailable[1] for a significant period of time.
If the system being upgraded provides critical services for your users or the network[2], you can reduce the downtime if you do a minimal system upgrade, as described in Section 4.4.4, “Minimal system upgrade”, followed by a kernel upgrade and reboot, and then upgrade the packages associated with your critical services. Upgrade these packages prior to doing the full upgrade described in Section 4.4.5, “Upgrading the system”. This way you can ensure that these critical services are running and available through the full upgrade process, and their downtime is reduced.
Although Debian tries to ensure that your system stays bootable at all times, there is always a chance that you may experience problems rebooting your system after the upgrade. Known potential issues are documented in this and the next chapters of these Release Notes.
For this reason it makes sense to ensure that you will be able to recover if your system should fail to reboot or, for remotely managed systems, fail to bring up networking.
If you are upgrading remotely via an ssh link it is recommended that you take the necessary precautions to be able to access the server through a remote serial terminal. There is a chance that, after upgrading the kernel and rebooting, you will have to fix the system configuration through a local console. Also, if the system is rebooted accidentally in the middle of an upgrade there is a chance you will need to recover using a local console.
For emergency recovery we generally recommend using the rescue mode of the bullseye Debian Installer. The advantage of using the installer is that you can choose between its many methods to find one that best suits your situation. For more information, please consult the section “Recovering a Broken System” in chapter 8 of the Installation Guide and the Debian Installer FAQ.
If that fails, you will need an alternative way to boot your system so you can access and repair it. One option is to use a special rescue or live install image. After booting from that, you should be able to mount your root file system and chroot into it to investigate and fix the problem.
The initramfs-tools
package includes a debug
shell[3] in the
initrds it generates. If for example the initrd is unable to mount your root
file system, you will be dropped into this debug shell which has basic commands
available to help trace the problem and possibly fix it.
Basic things to check are: presence of correct device files in
/dev
; what modules are loaded (cat
/proc/modules
); output of dmesg for errors loading
drivers. The output of dmesg will also show what device
files have been assigned to which disks; you should check that against the
output of echo $ROOT
to make sure that the root file system
is on the expected device.
If you do manage to fix the problem, typing exit
will quit
the debug shell and continue the boot process at the point it failed. Of
course you will also need to fix the underlying problem and regenerate the
initrd so the next boot won't fail again.
If the boot fails under systemd, it is possible to obtain a
debug root shell by changing the kernel command line. If the
basic boot succeeds, but some services fail to start, it
may be useful to add systemd.unit=rescue.target
to the kernel parameters.
Otherwise, the kernel parameter
systemd.unit=emergency.target
will provide you
with a root shell at the earliest possible point. However, this
is done before mounting the root file system with read-write
permissions. You will have to do that manually with:
# mount -o remount,rw /
More information on debugging a broken boot under systemd can be found in the Diagnosing Boot Problems article.
Important | |
---|---|
If you are using some VPN services (such as |
In order to gain extra safety margin when upgrading remotely, we suggest that you run upgrade processes in the virtual console provided by the screen program, which enables safe reconnection and ensures the upgrade process is not interrupted even if the remote connection process temporarily fails.
The upgrade process described in this chapter has been designed for “pure” Debian stable systems. APT controls what is installed on your system. If your APT configuration mentions additional sources besides buster, or if you have installed packages from other releases or from third parties, then to ensure a reliable upgrade process you may wish to begin by removing these complicating factors.
The main configuration file that APT uses to decide what sources
it should download packages from is
/etc/apt/sources.list
, but it can also use
files in the /etc/apt/sources.list.d/
directory - for details see sources.list(5).
If your system is using multiple source-list files then you will
need to ensure they stay consistent.
Direct upgrades from Debian releases older than 10 (buster) are not supported. Display your Debian version with:
$ cat /etc/debian_version
Please follow the instructions in the Release Notes for Debian 10 to upgrade to Debian 10 first.
Below there are two methods for finding installed packages that did not come from Debian, using either aptitude or apt-forktracer. Please note that neither of them are 100% accurate (e.g. the aptitude example will list packages that were once provided by Debian but no longer are, such as old kernel packages).
$ aptitude search '?narrow(?installed, ?not(?origin(Debian)))' $ apt-forktracer | sort
This procedure assumes your system has been updated to the latest point release of buster. If you have not done this or are unsure, follow the instructions in Section A.1, “Upgrading your buster system”.
You should make sure the package database is ready before proceeding
with the upgrade. If you are a user of another package manager like
aptitude
or synaptic
, review any pending actions. A
package scheduled for installation or removal
might interfere with the upgrade procedure. Note that correcting this is
only possible if your APT source-list files still point to
buster and not to
stable or bullseye; see
Section A.2, “Checking your APT source-list files”.
It is a good idea to remove obsolete packages from your system before upgrading. They may introduce complications during the upgrade process, and can present security risks as they are no longer maintained.
A previous upgrade may have left unused copies of configuration files; old versions of configuration files, versions supplied by the package maintainers, etc. Removing leftover files from previous upgrades can avoid confusion. Find such leftover files with:
# find /etc -name '*.dpkg-*' -o -name '*.ucf-*' -o -name '*.merge-error'
For APT source lines referencing the security archive, the format
has changed slightly along with the release name, going from
buster/updates
to
bullseye-security
; see
Section 5.1.2, “Changed security archive layout”.
If you have listed the proposed-updates
section in
your APT source-list files, you should remove it before
attempting to upgrade your system. This is a precaution to reduce the
likelihood of conflicts.
If you have any non-Debian packages on your system, you should be aware that these may be removed during the upgrade because of conflicting dependencies. If these packages were installed by adding an extra package archive in your APT source-list files, you should check if that archive also offers packages compiled for bullseye and change the source item accordingly at the same time as your source items for Debian packages.
Some users may have unofficial backported “newer” versions of packages that are in Debian installed on their buster system. Such packages are most likely to cause problems during an upgrade as they may result in file conflicts[4]. Section 4.5, “Possible issues during upgrade” has some information on how to deal with file conflicts if they should occur.
If you have configured APT to install certain packages from a distribution
other than stable (e.g. from testing), you may have to change your APT pinning
configuration (stored in /etc/apt/preferences
and /etc/apt/preferences.d/
) to allow
the upgrade of packages to the versions in the new stable release. Further
information on APT pinning can be found in apt_preferences(5).
Regardless of the method used for upgrading, it is recommended that you check the status of all packages first, and verify that all packages are in an upgradable state. The following command will show any packages which have a status of Half-Installed or Failed-Config, and those with any error status.
# dpkg --audit
You could also inspect the state of all packages on your system using aptitude or with commands such as
# dpkg -l | pager
or
# dpkg --get-selections "*" > ~/curr-pkgs.txt
It is desirable to remove any holds before upgrading. If any package that is essential for the upgrade is on hold, the upgrade will fail.
Note that aptitude uses a different method for registering packages that are on hold than apt and dselect. You can identify packages on hold for aptitude with
# aptitude search "~ahold"
If you want to check which packages you had on hold for apt, you should use
# dpkg --get-selections | grep 'hold$'
If you changed and recompiled a package locally, and didn't rename it or put an epoch in the version, you must put it on hold to prevent it from being upgraded.
The “hold” package state for apt can be changed using:
# echo package_name
hold | dpkg --set-selections
Replace hold
with install
to unset the
“hold” state.
If there is anything you need to fix, it is best to make sure your APT source-list files still refer to buster as explained in Section A.2, “Checking your APT source-list files”.
Before starting the upgrade you must reconfigure APT source-list
files (/etc/apt/sources.list
and files under
/etc/apt/sources.list.d/
) to add sources for
bullseye
and typically to remove sources
for buster
.
APT will consider all packages that can be found via any configured archive, and install the package with the highest version number, giving priority to the first entry in the files. Thus, if you have multiple mirror locations, list first the ones on local hard disks, then CD-ROMs, and then remote mirrors.
A release can often be referred to both by its codename (e.g.
buster
, bullseye
) and by
its status name (i.e. oldstable
, stable
,
testing
, unstable
). Referring to
a release by its codename has the advantage that you will never be surprised by
a new release and for this reason is the approach taken here. It does of
course mean that you will have to watch out for release announcements yourself.
If you use the status name instead, you will just see loads of updates for
packages available as soon as a release has happened.
Debian provides two announcement mailing lists to help you stay up to date on relevant information related to Debian releases:
By
subscribing to the Debian announcement mailing list,
you will receive a notification every time Debian makes a new
release. Such as when bullseye
changes from e.g. testing
to
stable
.
By subscribing to the Debian security announcement mailing list, you will receive a notification every time Debian publishes a security announcement.
On new installations the default is for APT to be set up to use the Debian APT CDN service, which should ensure that packages are automatically downloaded from a server near you in network terms. As this is a relatively new service, older installations may have configuration that still points to one of the main Debian Internet servers or one of the mirrors. If you haven't done so yet, it is recommended to switch over to the use of the CDN service in your APT configuration.
To make use of the CDN service, add a line like this to your APT source
configuration (assuming you are using main
and
contrib
):
deb http://deb.debian.org/debian bullseye main contrib
After adding your new sources, disable the previously existing
“deb
” lines by placing a hash sign
(#
) in front of them.
However, if you get better results using a specific mirror that is close to you in network terms, this option is still available.
Debian mirror addresses can be found at https://www.debian.org/distrib/ftplist (look at the “list of Debian mirrors” section).
For example, suppose your closest Debian mirror is
http://mirrors.kernel.org
. If you inspect that
mirror with a web browser, you will notice that the main
directories are organized like this:
http://mirrors.kernel.org/debian/dists/bullseye/main/binary-ppc64el/... http://mirrors.kernel.org/debian/dists/bullseye/contrib/binary-ppc64el/...
To configure APT to use a given mirror, add a line like this (again,
assuming you are using main
and
contrib
):
deb http://mirrors.kernel.org/debian bullseye main contrib
Note that the “dists
” is added implicitly, and the arguments
after the release name are used to expand the path into multiple directories.
Again, after adding your new sources, disable the previously existing archive entries.
Instead of using remote package mirrors, you may wish to modify the APT source-list files to use a mirror on a local disk (possibly mounted over NFS).
For example, your package mirror may be under
/var/local/debian/
, and have main directories like this:
/var/local/debian/dists/bullseye/main/binary-ppc64el/... /var/local/debian/dists/bullseye/contrib/binary-ppc64el/...
To use this with apt
, add this line to your
sources.list
file:
deb file:/var/local/debian bullseye main contrib
Note that the “dists
” is added implicitly, and the arguments
after the release name are used to expand the path into multiple directories.
After adding your new sources, disable the previously existing
archive entries in the APT source-list files by placing a
hash sign (#
) in front of them.
If you want to use only DVDs (or CDs or Blu-ray
Discs), comment out the existing entries in all the APT source-list files
by placing a hash sign (#
) in front of them.
Make sure there is a line in /etc/fstab
that enables
mounting your CD-ROM drive at the /media/cdrom
mount point. For example, if /dev/sr0
is your CD-ROM drive, /etc/fstab
should contain a line
like:
/dev/sr0 /media/cdrom auto noauto,ro 0 0
Note that there must be no spaces between the words
noauto,ro
in the fourth field.
To verify it works, insert a CD and try running
# mount /media/cdrom # this will mount the CD to the mount point # ls -alF /media/cdrom # this should show the CD's root directory # umount /media/cdrom # this will unmount the CD
Next, run:
# apt-cdrom add
for each Debian Binary CD-ROM you have, to add the data about each CD to APT's database.
The recommended way to upgrade from previous Debian releases is to use the package management tool apt.
Note | |
---|---|
apt is meant for interactive use, and should not be used in scripts. In scripts one should use apt-get, which has a stable output better suitable for parsing. |
Don't forget to mount all needed partitions (notably the root and
/usr
partitions) read-write, with a command like:
# mount -o remount,rw /mountpoint
Next you should double-check that the APT source entries (in
/etc/apt/sources.list
and files under
/etc/apt/sources.list.d/
) refer either to
“bullseye
” or to
“stable
”. There should not be any sources
entries pointing to buster.
Note | |
---|---|
Source lines for a CD-ROM might sometimes refer to
“ |
It is strongly recommended that you use the /usr/bin/script program to record a transcript of the upgrade session. Then if a problem occurs, you will have a log of what happened, and if needed, can provide exact information in a bug report. To start the recording, type:
# script -t 2>~/upgrade-bullseyestep
.time -a ~/upgrade-bullseyestep
.script
or similar. If you have to rerun the typescript (e.g. if you have to reboot the
system) use different step
values to indicate which
step of the upgrade you are logging. Do not put the typescript file in a
temporary directory such as /tmp
or
/var/tmp
(files in those directories may be deleted during
the upgrade or during any restart).
The typescript will also allow you to review information that has scrolled
off-screen. If you are at the system's console, just switch to VT2 (using
Alt+F2)
and, after logging in, use
less -R ~root/upgrade-bullseye.script
to view
the file.
After you have completed the upgrade, you can stop script by
typing exit
at the prompt.
apt will also log the changed package states in
/var/log/apt/history.log
and the terminal output in
/var/log/apt/term.log
. dpkg will,
in addition, log all package state changes in
/var/log/dpkg.log
. If you use aptitude,
it will also log state changes in /var/log/aptitude
.
If you have used the -t switch for script you can use the scriptreplay program to replay the whole session:
# scriptreplay ~/upgrade-bullseyestep
.time ~/upgrade-bullseyestep
.script
First the list of available packages for the new release needs to be fetched. This is done by executing:
# apt update
Note | |
---|---|
Users of apt-secure may find issues when using aptitude or apt-get. For apt-get, you can use apt-get update --allow-releaseinfo-change. |
You have to make sure before upgrading your system that you will have sufficient
hard disk space when you start the full system upgrade described in Section 4.4.5, “Upgrading the system”. First, any package needed for installation that
is fetched from the network is stored in
/var/cache/apt/archives
(and the
partial/
subdirectory, during download), so you must make
sure you have enough space on the file system partition that holds
/var/
to temporarily download the packages that will be
installed in your system. After the download, you will probably need more
space in other file system partitions in order to both install upgraded
packages (which might contain bigger binaries or more data) and new packages
that will be pulled in for the upgrade. If your system does not have
sufficient space you might end up with an incomplete upgrade that is
difficult to recover from.
apt can show you detailed information about the disk space needed for the installation. Before executing the upgrade, you can see this estimate by running:
# apt -o APT::Get::Trivial-Only=true full-upgrade [ ... ] XXX upgraded, XXX newly installed, XXX to remove and XXX not upgraded. Need to get xx.xMB of archives. After this operation, AAAMB of additional disk space will be used.
Note | |
---|---|
Running this command at the beginning of the upgrade process may give an error, for the reasons described in the next sections. In that case you will need to wait until you've done the minimal system upgrade as in Section 4.4.4, “Minimal system upgrade” before running this command to estimate the disk space. |
If you do not have enough space for the upgrade, apt will warn you with a message like this:
E: You don't have enough free space in /var/cache/apt/archives/.
In this situation, make sure you free up space beforehand. You can:
Remove packages that have been previously downloaded for installation (at
/var/cache/apt/archives
). Cleaning up the package cache by
running apt clean will remove all previously downloaded
package files.
Remove forgotten packages. If you have used aptitude or apt to manually install packages in buster it will have kept track of those packages you manually installed, and will be able to mark as redundant those packages pulled in by dependencies alone which are no longer needed due to a package being removed. They will not mark for removal packages that you manually installed. To remove automatically installed packages that are no longer used, run:
# apt autoremove
You can also use deborphan, debfoster, or cruft to find redundant packages. Do not blindly remove the packages these tools present, especially if you are using aggressive non-default options that are prone to false positives. It is highly recommended that you manually review the packages suggested for removal (i.e. their contents, sizes, and descriptions) before you remove them.
Remove packages that take up too much space and are not currently
needed (you can always reinstall them after the upgrade). If you have
popularity-contest
installed, you can use
popcon-largest-unused to list the packages you do not use
that occupy the most space. You can find the packages that just
take up the most disk space with dpigs (available in the
debian-goodies
package) or with
wajig (running wajig size
).
They can also be found with
aptitude
. Start
aptitude in full-terminal mode,
select → , press l and enter
~i
, then press S and enter
~installsize
. This will give you a handy list to work
with.
Remove translations and localization files from the system if they
are not needed. You can install the localepurge
package and configure it so
that only a few selected locales are kept in the system. This will
reduce the disk space consumed at
/usr/share/locale
.
Temporarily move to another system, or permanently remove, system logs
residing under /var/log/
.
Use a temporary /var/cache/apt/archives
: You
can use a temporary cache directory from another filesystem
(USB storage device, temporary hard disk,
filesystem already in use, ...).
Note | |
---|---|
Do not use an NFS mount as the network connection could be interrupted during the upgrade. |
For example, if you have a USB drive mounted on /media/usbkey
:
remove the packages that have been previously downloaded for installation:
# apt clean
copy the directory
/var/cache/apt/archives
to the
USB drive:
# cp -ax /var/cache/apt/archives /media/usbkey/
mount the temporary cache directory on the current one:
# mount --bind /media/usbkey/archives /var/cache/apt/archives
after the upgrade, restore the original
/var/cache/apt/archives
directory:
# umount /var/cache/apt/archives
remove the remaining /media/usbkey/archives
.
You can create the temporary cache directory on whatever filesystem is mounted on your system.
Do a minimal upgrade of the system (see Section 4.4.4, “Minimal system upgrade”) or partial upgrades of the system followed by a full upgrade. This will make it possible to upgrade the system partially, and allow you to clean the package cache before the full upgrade.
Note that in order to safely remove packages, it is advisable to switch your APT source-list files back to buster as described in Section A.2, “Checking your APT source-list files”.
Important | |
---|---|
If you are upgrading remotely, be aware of Section 5.1.22, “No new SSH connections possible during upgrade”. |
In some cases, doing the full upgrade (as described below) directly might remove large numbers of packages that you will want to keep. We therefore recommend a two-part upgrade process: first a minimal upgrade to overcome these conflicts, then a full upgrade as described in Section 4.4.5, “Upgrading the system”.
To do this, first run:
# apt upgrade --without-new-pkgs
This has the effect of upgrading those packages which can be upgraded without requiring any other packages to be removed or installed.
The minimal system upgrade can also be useful when the system is tight on space and a full upgrade cannot be run due to space constraints.
If the apt-listchanges
package is
installed, it will (in its default configuration) show important information
about upgraded packages in a pager after downloading the packages. Press
q after reading to exit the pager and continue the
upgrade.
Once you have taken the previous steps, you are now ready to continue with the main part of the upgrade. Execute:
# apt full-upgrade
This will perform a complete upgrade of the system, installing the newest available versions of all packages, and resolving all possible dependency changes between packages in different releases. If necessary, it will install some new packages (usually new library versions, or renamed packages), and remove any conflicting obsoleted packages.
When upgrading from a set of CDs/DVDs/BDs, you will probably be asked to insert specific discs at several points during the upgrade. You might have to insert the same disc multiple times; this is due to inter-related packages that have been spread out over the discs.
New versions of currently installed packages that cannot be upgraded without
changing the install status of another package will be left at their current
version (displayed as “held back”). This can be resolved by either using
aptitude to choose these packages for installation or by
trying apt install
.
package
The following sections describe known issues that might appear during an upgrade to bullseye.
In some cases the apt full-upgrade step can fail after downloading packages with:
E: Could not perform immediate configuration on 'package
'. Please see man 5 apt.conf under APT::Immediate-Configure for details.
If that happens, running apt full-upgrade -o APT::Immediate-Configure=0 instead should allow the upgrade to proceed.
Another possible workaround for this problem is to temporarily add both buster and bullseye sources to your APT source-list files and run apt update.
The upgrade process to bullseye might ask for the removal of packages on the system. The precise list of packages will vary depending on the set of packages that you have installed. These release notes give general advice on these removals, but if in doubt, it is recommended that you examine the package removals proposed by each method before proceeding. For more information about packages obsoleted in bullseye, see Section 4.8, “Obsolete packages”.
Sometimes it's necessary to enable the APT::Force-LoopBreak
option in APT to be able to temporarily remove an essential package due to a
Conflicts/Pre-Depends loop. apt will alert you of this
and abort the upgrade. You can work around this by specifying the option -o
APT::Force-LoopBreak=1
on the apt command
line.
It is possible that a system's dependency structure can be so corrupt as to require manual intervention. Usually this means using apt or
# dpkg --remove package_name
to eliminate some of the offending packages, or
# apt -f install # dpkg --configure --pending
In extreme cases you might have to force re-installation with a command like
# dpkg --install /path/to/package_name.deb
File conflicts should not occur if you upgrade from a “pure” buster system, but can occur if you have unofficial backports installed. A file conflict will result in an error like:
Unpacking<package-foo>
(from<package-foo-file>
) ... dpkg: error processing<package-foo>
(--install): trying to overwrite `<some-file-name>
', which is also in package<package-bar>
dpkg-deb: subprocess paste killed by signal (Broken pipe) Errors were encountered while processing:<package-foo>
You can try to solve a file conflict by forcibly removing the package mentioned on the last line of the error message:
# dpkg -r --force-depends package_name
After fixing things up, you should be able to resume the upgrade by repeating the previously described apt commands.
During the upgrade, you will be asked questions regarding the configuration
or re-configuration of several packages. When you are asked if any file in
the /etc/init.d
directory, or the
/etc/manpath.config
file should be replaced by the
package maintainer's version, it's usually necessary to answer “yes” to
ensure system consistency. You can always revert to the old versions, since
they will be saved with a .dpkg-old
extension.
If you're not sure what to do, write down the name of the package or file and sort things out at a later time. You can search in the typescript file to review the information that was on the screen during the upgrade.
If you are running the upgrade using the system's local console you might find that at some points during the upgrade the console is shifted over to a different view and you lose visibility of the upgrade process. For example, this may happen in systems with a graphical interface when the display manager is restarted.
To recover the console where the upgrade was running you will have to use Ctrl+Alt+F1 (if in the graphical startup screen) or Alt+F1 (if in the local text-mode console) to switch back to the virtual terminal 1. Replace F1 with the function key with the same number as the virtual terminal the upgrade was running in. You can also use Alt+Left Arrow or Alt+Right Arrow to switch between the different text-mode terminals.
This section explains how to upgrade your kernel and identifies potential
issues related to this upgrade. You can either install one of the linux-image-*
packages provided by Debian, or
compile a customized kernel from source.
Note that a lot of information in this section is based on the assumption that
you will be using one of the modular Debian kernels, together with initramfs-tools
and udev
. If you choose to use a custom kernel that
does not require an initrd or if you use a different initrd generator, some of
the information may not be relevant for you.
When you full-upgrade from buster to bullseye, it is strongly recommended that you install a linux-image-* metapackage, if you have not done so before. These metapackages will automatically pull in a newer version of the kernel during upgrades. You can verify whether you have one installed by running:
# dpkg -l "linux-image*" | grep ^ii | grep -i meta
If you do not see any output, then you will either need to install a new linux-image package by hand or install a linux-image metapackage. To see a list of available linux-image metapackages, run:
# apt-cache search linux-image- | grep -i meta | grep -v transition
If you are unsure about which package to select, run uname
-r
and look for a package with a similar name. For example, if you
see “4.9.0-8-amd64
”, it is recommended that you install
linux-image-amd64
.
You may also use apt to see a long
description of each package in order to help choose the best one
available. For example:
# apt show linux-image-amd64
You should then use apt install
to install it.
Once this new kernel is installed you should reboot at the next
available opportunity to get the benefits provided by the new kernel
version. However, please have a look at Section 5.1.24, “Things to do post upgrade before rebooting”
before performing the first reboot after the upgrade.
For the more adventurous there is an easy way to compile your own custom
kernel on Debian. Install the kernel sources, provided in the linux-source
package. You can make use of the
deb-pkg
target available in the sources' makefile for
building a binary package. More information can be found in the Debian Linux Kernel
Handbook, which can also be found as the debian-kernel-handbook
package.
If possible, it is to your advantage to upgrade the kernel package separately
from the main full-upgrade
to reduce the chances of a
temporarily non-bootable system.
Note that this should only be done after the
minimal upgrade process described in Section 4.4.4, “Minimal system upgrade”.
After the upgrade there are several things you can do to prepare for the next release.
Remove newly redundant or obsolete packages as described in Section 4.4.3, “Make sure you have sufficient space for the upgrade” and Section 4.8, “Obsolete packages”. You should review which configuration files they use and consider purging the packages to remove their configuration files. See also Section 4.7.1, “Purging removed packages”.
It is generally advisable to purge removed packages. This is especially true if these have been removed in an earlier release upgrade (e.g. from the upgrade to buster) or they were provided by third-party vendors. In particular, old init.d scripts have been known to cause issues.
Caution | |
---|---|
Purging a package will generally also purge its log files, so you might want to back them up first. |
The following command displays a list of all removed packages that may have configuration files left on the system (if any):
# dpkg -l | awk '/^rc/ { print $2 }'
The packages can be removed by using apt purge. Assuming you want to purge all of them in one go, you can use the following command:
# apt purge $(dpkg -l | awk '/^rc/ { print $2 }')
If you use aptitude
, you
can also use the following alternative to the commands above:
# aptitude search '~c' # aptitude purge '~c'
Introducing lots of new packages, bullseye also retires and omits quite a few old packages that were in buster. It provides no upgrade path for these obsolete packages. While nothing prevents you from continuing to use an obsolete package where desired, the Debian project will usually discontinue security support for it a year after bullseye's release[5], and will not normally provide other support in the meantime. Replacing them with available alternatives, if any, is recommended.
There are many reasons why packages might have been removed from the distribution: they are no longer maintained upstream; there is no longer a Debian Developer interested in maintaining the packages; the functionality they provide has been superseded by different software (or a new version); or they are no longer considered suitable for bullseye due to bugs in them. In the latter case, packages might still be present in the “unstable” distribution.
Some package management front-ends provide easy ways of finding installed packages that are no longer available from any known repository. The aptitude textual user interface lists them in the category “Obsolete and Locally Created Packages”, and they can be listed and purged from the commandline with:
# aptitude search '~o' # aptitude purge '~o'
The Debian Bug Tracking System often provides additional information on why the package was removed. You should review both the archived bug reports for the package itself and the archived bug reports for the ftp.debian.org pseudo-package.
For a list of obsolete packages for Bullseye, please refer to Section 5.3.1, “Noteworthy obsolete packages”.
Some packages from buster may have been replaced in bullseye by transitional dummy packages, which are empty placeholders designed to simplify upgrades. If for instance an application that was formerly a single package has been split into several, a transitional package may be provided with the same name as the old package and with appropriate dependencies to cause the new ones to be installed. After this has happened the redundant dummy package can be safely removed.
The package descriptions for transitional dummy packages usually indicate
their purpose. However, they are not uniform; in particular, some
“dummy” packages are designed to be kept installed, in order
to pull in a full software suite, or track the current latest version of
some program. You might also find deborphan with the
--guess-
options (e.g.
*
--guess-dummy
) useful to detect transitional dummy
packages on your system.
[1] If the debconf priority is set to a very high level you might prevent configuration prompts, but services that rely on default answers that are not applicable to your system will fail to start.
[2] For example: DNS or DHCP services, especially when there is no redundancy or failover. In the DHCP case end-users might be disconnected from the network if the lease time is lower than the time it takes for the upgrade process to complete.
[3] This feature can be disabled by adding the parameter
panic=0
to your boot parameters.
[4] Debian's package management system normally does not allow a package to remove or replace a file owned by another package unless it has been defined to replace that package.
[5] Or for as long as there is not another release in that time frame. Typically only two stable releases are supported at any given time.