Difference between revisions of "System resurrection"
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== Restoring the binary packages on the broken system == | == Restoring the binary packages on the broken system == | ||
| − | + | There are a couple of methods that can be used to restore binary packages to a broken system. | |
| + | |||
| + | === Chroot/Emerge Method === | ||
| + | |||
| + | The first step can be used for lightly damaged systems that still have a functional Portage and to which you can still <tt>chroot</tt> and perform all basic Linux commands. To use this method, you would mount your broken system to <tt>/mnt/broken</tt> using steps similar to the way we set up <tt>/mnt/rescue</tt>, above. | ||
| + | |||
| + | Before or after chrooting, copy the binary packages created in the step above in the exact same location on your broken system (e.g. in <tt>/usr/portage/packages/'''sys-devel'''</tt> in the case of <tt>'''sys-devel'''/gcc</tt>). | ||
| + | |||
| + | Once chrooted inside your system, you will be able to merge your packages using <tt>emerge</tt> as follows: | ||
<pre> | <pre> | ||
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</pre> | </pre> | ||
| − | + | === Tbz2 Extract Method === | |
| + | |||
| + | This alternate method for installing binary packages is simpler and does not require the use of the <tt>chroot</tt> command. To prepare for using this approach, you just need to mount all key filesystems to <tt>/mnt/broken</tt> as follows -- and bind mounts are not necessary: | ||
<pre> | <pre> | ||
| − | # | + | # install -d /mnt/broken |
| + | # mount /dev/sdaX /mnt/broken | ||
| + | # mount /dev/sdaY /mnt/broken/usr | ||
</pre> | </pre> | ||
| − | + | Then, use the following commands to extract the .tbz2 archive to your broken filesystem that you mounted at <tt>/mnt/broken</tt>: | |
| + | |||
| + | <pre> | ||
| + | # tar xjpvf gcc-4.4.5.tbz2 -C /mnt/broken | ||
| + | </pre> | ||
You will see a note about the trailing garbage at the end of the file being ignored. This is normal -- tar is ignoring the Portage .tbz2 metadata that is tacked on to the end of the file. | You will see a note about the trailing garbage at the end of the file being ignored. This is normal -- tar is ignoring the Portage .tbz2 metadata that is tacked on to the end of the file. | ||
| + | |||
| + | At this point, you can set up bind mounts (see <tt>/mnt/rescue</tt> example earlier in this document for those steps), <tt>chroot</tt> inside <tt>/mnt/broken</tt>, and perform a few tests to determine if your issue has been resolved. | ||
= Various weird issues = | = Various weird issues = | ||
Revision as of 17:06, 23 March 2011
Although it is always possible to resurrect a machine back to life by reinstalling it, it is not always suitable to reinstall from scratch and sometimes the best is to try to fix a broken system even with as a last resort option before a full system reinstallation. Here are some ideas on how to resurrect a dead Funtoo system without reinstalling everything from scratch.
Contents |
Core package removal
Several packages at the heart of your Funtoo system, these mainly are:
| Component | Package | Functional role |
|---|---|---|
| GNU Binutils | sys-devel/binutils | Binutils are a set a tools (linker, assembler...) used behind the scene by the GNU Compiler Collection to produce executable files. |
| GNU Compiler collection (GCC) | sys-devel/gcc | GCC is a collection of compilers or several languages (FORTRAN, Java, C and C++, plus some libraries like the Standard Template Library or STL). A wide spectrum of software in a Funtoo system is written in C/C++. |
| C Library | sys-libs/glibc | The C library contains an implementation of a wide range of commonly needed functionalities like memory allocation, strings manipulation, I/O operations and so on. It is maybe of one most critical system components as nearly everything on a Funtoo system depends on this component (including the Python interpreter which executes the vairous Python scripts at the heart of the Funtoo core utilities and package management system). |
| Z library | sys-libs/zlib | This library contain several lossless compression/decompression routines.It is used by many other components on a Funtoo system like the bzip2/bunzip2 commands (app-arch/bzip2) for example (xz archive utilities depends on another standalone set of libraries). |
Building binary packages
The best approach for critical system repair is to boot on a SystemRescueCD or other similar LiveCD, and use this as working platform to resurrect your system.
For creating binary packages, you can use any of the following options for a source environment:
- Use the most recent Funtoo stage3 for your architecture.
- If available, use a recent system backup (e.g. snapshot if you use a BTRFS or ZFS filesystem or LVM volume, or a tar or cpio backup of your hard drive)
On a working Linux system, which can be either your broken system booted with a LiveCD, or another system on your network, you will want to build a chroot environment using the "source environment" you selected above, and use this as a platform for building binary packages to restore your system. Once these packages are created, they can be copied to your broken system and installed using the steps later in this document.
The binary package creation environment would typically be set up as follows:
# install -d /mnt/rescue # tar xpvf backup.tar.bz2 -C /mnt/rescue # cp /etc/resolv.conf /mnt/rescue/etc # mount --bind /proc /mnt/rescue/proc # mount --bind /sys /mnt/rescue/sys # mount --bind /dev /mnt/rescue/dev # mount --bind /dev/pts /mnt/rescue/dev/pts # chroot /mnt/rescue # source /etc/profile # env-update
No matter of the way you jump in a functional Funtoo/Gentoo environment, the magic command to create a binary package archive once inside is quickpkg. quickpkg will capture the package in the exact form it is actually deployed on the environment and create an archive of it placed in /usr/portage/packages/<package-category>/<package-name>-<package-version>.tbz2.
In the following example capture everything installed within the "source environment" that is related sys-devel/gcc (4.4.5 is present on the system) is captured in a single archive named gcc-4.4.5.tbz2 located in /usr/portage/packages/sys-devel:
# quickpkg sys-devel/gcc
If you need to recompile a package instead of archiving an already deployed version (and of course without installing it on your "source environment"), just do:
# emerge --buildpkgonly sys-devel/gcc
Restoring the binary packages on the broken system
There are a couple of methods that can be used to restore binary packages to a broken system.
Chroot/Emerge Method
The first step can be used for lightly damaged systems that still have a functional Portage and to which you can still chroot and perform all basic Linux commands. To use this method, you would mount your broken system to /mnt/broken using steps similar to the way we set up /mnt/rescue, above.
Before or after chrooting, copy the binary packages created in the step above in the exact same location on your broken system (e.g. in /usr/portage/packages/sys-devel in the case of sys-devel/gcc).
Once chrooted inside your system, you will be able to merge your packages using emerge as follows:
# emerge -k sys-devel/gcc
Tbz2 Extract Method
This alternate method for installing binary packages is simpler and does not require the use of the chroot command. To prepare for using this approach, you just need to mount all key filesystems to /mnt/broken as follows -- and bind mounts are not necessary:
# install -d /mnt/broken # mount /dev/sdaX /mnt/broken # mount /dev/sdaY /mnt/broken/usr
Then, use the following commands to extract the .tbz2 archive to your broken filesystem that you mounted at /mnt/broken:
# tar xjpvf gcc-4.4.5.tbz2 -C /mnt/broken
You will see a note about the trailing garbage at the end of the file being ignored. This is normal -- tar is ignoring the Portage .tbz2 metadata that is tacked on to the end of the file.
At this point, you can set up bind mounts (see /mnt/rescue example earlier in this document for those steps), chroot inside /mnt/broken, and perform a few tests to determine if your issue has been resolved.
Various weird issues
P1: I have a local distfiles mirror and wget complains about not being able to resolve 'localhost'.
S1: libnss (which handles name resolution) is probably damaged or suffers of inconsistencies, in your /etc/make.conf, change 'localhost' in GENTOO_MIRRORS for 127.0.0.1 (IPv4) or ::1 (IPv6)
P2: Same problem as described in P1 but I use another machine on my network or a public mirror on the Internet
S2: See the solution given in S1 but with providing the IP of the machine you are downloading for.
