|Summary help replacing me|
|Reverting to older versions of packages: why and how.|
|Arch Build System|
|LVM – how to enable snapshots and how to revert to their state|
This guide will show you how to downgrade a package to a previous version. Downgrading a package isn't normally recommended and is often only necessary when a bug is introduced in the current package.
Before downgrading, consider why you are doing so. If it is because of a bug, please help both Arch and upstream developers by spending a few minutes reporting the bug on the Arch bug tracker or on the parent project itself. Because Arch is a rolling release distribution you will likely be continously working with new packages and will experience a bug from time to time.
Both we and the upstream developers would appreciate the effort. That extra bit of information could save us hours of testing and debugging and also helps us release more stable software.
The process of downgrading is that of uninstalling the current package and installing a previous version. The previous version can be an immediate version (the package version directly before it) or to a number of versions prior.
The reasons for downgrading include (among others): that the current version has a bug, does not yet contain the desired functionality, or was done for experimental reasons. In any of these cases, the user has chosen that it would be less problematic to revert to a previous version than to wait for a new release.
Downgrading a package may mean that other packages may have to be downgraded with it. For those that have installed a good amount of experimental or testing packages, and edited a good deal of configurations, it may be preferable to re-install the system rather than trying to downgrade.
However, the user must keep in mind the following points:
- Consider the dependencies of each program. The required libraries often change with each version, and the functionality of associated files may be completely different from previous ones. The solution will require changing these to earlier versions as well.
- Consider if the necessary files have been removed from the system and are even going to be available from any source. Arch Linux's rolling release system of repositories are automatically upgraded without saving any older versions. See more about this problem below.
- Be careful with changes to configuration files and scripts. At this point in time, we will rely upon pacman to handle this for us, as long as we do not bypass any safeguards it contains.
The Arch Rollback Machine concept is being developed and awaiting useful incorporation into pacman. Once that occurs, this will become automated.
How to downgrade a package
- Q: I just ran
pacman -Syuand package XYZ was upgraded to version N from version M. This package is causing problems on my computer, how can I downgrade from version N to the older version M?
- A: You may be able to downgrade the package trivially by visiting
/var/cache/pacman/pkgon your system and seeing if the older version of the package is stored there. (If you have not run
pacman -Sccrecently, it should be there). If the package is there, you can install that version using
pacman -U /var/cache/pacman/pkg/pkgname-olderpkgver.pkg.tar.gz.
This process will remove the current package, will carefully calculate all of the dependency changes, and will install the older version you have chosen with the proper dependencies down the line.
There is also a package in the AUR called AUR. This is a simple Bash script which will look in your cache for older versions of packages. It will also search the A.R.M. if there is no package in your cache. You can then select a package to install. It basically just automates the processes outlined here. Check
downgrade --help for usage information.
One more powerful tool is namedAUR, and it works with pacman log's also, can downgrade packages from ARM, local cache, and work with list of packages (if your system unstable after upgrade of some packages, and you unsure about package name)
Downgrading the kernel
If you are unable to boot after a kernel update, then you can downgrade the kernel via a live cd. Use a fairly recent Arch Linux installation medium. When it has booted, mount the partition with your system on, e.g., /mnt and if you have /boot or /var on separate partitions, mount them there as well (mount /dev/sdc3 /mnt/boot). Then mount proc etc,
mount -t proc proc /mnt/proc mount -t sysfs sys /mnt/sys mount -o bind /dev /mnt/dev
and finally chroot into the system chroot /mnt /bin/bash. Here you can go to /var/cache/pacman/pkg and downgrade the packages. At least downgrade linux, linux-headers and any kernel modules, e.g.
pacman -U linux-3.5.6-1-x86_64.pkg.tar.xz linux-headers-3.5.6-1-x86_64.pkg.tar.xz virtualbox-host-modules-4.2.0-5-x86_64.pkg.tar.xz
exit the chroot, reboot and you should be done.
If you have a more exotic setup (lvm, encryption, ...), see this post: http://sch1zo.github.com/blog/2012/05/08/downgrading-a-bad-kernel-on-arch-with-luks-and-lvm/
Finding Your Older Version
There are three ways to do this.
If you can not find older versions on your system, check if one of the mirrors is out of sync, and get it from there. Click here to see the status of mirrors.
The Arch Rollback Machine (ARM) contains archived snapshots of all the repos going back to 1 November 2009. The site is in a state of flux as of this date (21 November 2009), and now has lost the items back thru 1 October 2008, as previously reported.
If you are interested in ARM, it would be best to view the introductory forum announcement and discussion, so as to stay abreast of the current progress of the project. The introductory forum thread is here.
It is said that the goal was to construct the urls in such a way as to facilitate easy wget+pacman scripting to "roll back" your system to a particular date. The automation process is not yet explained. To just manually search for a particular package, one can use the search page which has been provided at ARM Search.
Re-Compile The Package
In worst-case scenario, if the package is not located anywhere else, you will need to compile the older version yourself. To do this you will need a PKGBUILD for the file; you could edit the existing PKGBUILD provided by ABS to use older sources, or you can visit https://www.archlinux.org/packages/ and search for the package you wish to downgrade. Once you find it, click "View Changes" and select "log". Locate the version you need and click on the path. Then just download the files located in that directory and build it with makepkg.
For AUR packages, currently the only way to get the older PKGBUILDs is at http://pkgbuild.com/git/aur-mirror.git/ or check the Unofficial User Repositories for precompiled binaries (they are sometimes out of date).
To change repository to ARM, remarks-out the old line and adds the appropriate directory location in the format:
[core] #Server=http://mirrors.gigenet.com/archlinux/core/os/i686 Server=http://arm.konnichi.com/2009/11/01/core/os/i686
In this example, the date section is taking whatever packages are available as of the date of November 1st, 2009. Please note that all repositories are snapshots of the official repositories. You need only change the mirror in
/etc/pacman.d/mirrorlist, placing an ARM mirror at the top.
e.g http://arm.konnichi.com/2009/11/01/$repo/os/i686 to sync all official repositories listed in
/etc/pacman.conf to the chosen ARM mirror then update with:
pacman -Syy # refresh the sync databases pacman -Suu # downgrade all packages with a lower version in the repos
This alone does not guarantee a seamless rollback as there are sometimes package conflicts with regards to version numbers, etc. If you know the repository it may be easier to visit the global mirror, e.g http://arm.konnichi.com/core/os/i686, note the omission of the date.
More info please see pacman.