Re: Migrate running IA32 system to Debian AMD 64?
mailarch@archivum.info wrote:
Hello,
I have a running critical production server, running Debian Sarge 32 Bits version.
I would like to migrate to Debian-AMD64 system, how can I do it, without interrupting for more
than 5 minutes my services which are running on it?
I mounted the ISO debian-31r0a-amd64-binary-1.iso at /mnt but I don't know how to start manually
the Debian installation program.
How can I start the install program manually?
I would like to install the Debian AMD64 distribution to a temporary device (USB key), then I do a chroot, if
all works fine I will try to boot on the USB key, and then if all works very well, I will copy the USB key
files to the old harddisk partition to complete the migration.
Is this possible?
My idea:
1. Compile a 64-bit kernel, with 32-bit emulation support.
2. Reboot into that new kernel, without changing any other programs.
The new kernel should work fine with the old 32-bit programs.
Assuming you have enough disk space, use debootstrap to
install a 64-bit installation in a chroot while the system is up
and running. (Take care not to start any
network sw in the chroot.) Your users will be using the 32-bit
software while you work.
Note that you can bind-mount directories from the 32-bit
system in the 64-bit chroot, so that directories like /home
are accessible from both 32-bit land and 64-bit land.
3. Do a gradual update by stopping one 32-bit service,
copying stuff over to the installed 64-bit service, and
restarting the 64-bit service instead of the 32-bit service.
Test that it works well before proceeding to the next service.
Downtime on each service will then be short. If something
doesn't work, restart the known working 32-bit service
before pondering what went wrong.
4. After a while, there is no 32-bit code left running. Wait some
days to be sure.
5. Finalize by removing the 32-bit stuff and make the 64-bit
root the real root instead of a chroot. (If you later need
to run some rare 32-bit only sw, install that in a chroot instead.)
I did something like this, but it was only a home machine. Still,
family members get upset if they can't check their mail whenever
they want to . . .
Helge Hafting
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