30 Oct
2020
30 Oct
'20
11:31 p.m.
Hello,
Perhaps of interest to those of you still on 32-bit installs¹,
Debian now has a "crossgrader" package that has just had its first
version uploaded to the "unstable" suite:
https://salsa.debian.org/crossgrading-team/debian-crossgrading/
I have used this manual process:
https://wiki.debian.org/CrossGrading
many times to go from i386 to amd64, but it is unsupported and scary
and depending on the exact packages you have installed can be very
tricky. It will ask you to approve actions that may destroy your
system.
I haven't yet had chance to try "crossgrader" myself yet, but I will
try it next time I have to do this. I would be interested in reading
your experiences of using it.
I gather that it would be wise to fully upgrade to the latest stable
release (buster) on i386 before trying to crossgrade to amd64,
either by this method or manually.
For those keen to switch to 64-bit, much of the benefits can be
obtained without most of the risk by only changing your kernel to
the amd64 architecture. After following the wiki article above to
the end of the "Install a kernel that supports both architectures in
userland" section, you would:
1. Connect to Xen Shell and use the "console" command if not already
in it.
2. Halt your VPS.
3. Use the Xen Shell "arch" command to switch to x86-64 bootloader.
4. Use the Xen Shell "boot" command to boot it.
5. When your own grub menu appears, select the amd64 kernel that is
listed, not the i686 one.
Provided everything seems to work okay you can then remove the i686
kernel packages, and the system will keep the -amd64 kernel packages
up to date. Your VPS is then a 64-bit one running a 64-bit kernel
but with almost entirely 32-bit userland.
Changing over the 32-bit userland by either the crossgrader package
or manually is where most of the complexity lies.
For context as to why you might want to switch away from 32-bit:
- The next major Xen release will remove 32-bit PV support. We'll
switch to PVH mode before then to allow remaining 32-bit guests to
still run.
- At the recent Xen Developer summit it was stated that "anyone
still running 32-bit PV is setting fire to 30% of their CPU".
- All manner of 32-bit-specific fixes, including security, are being
delayed and overlooked in the upstream Linux kernel, so switching
away from running an i686 kernel would be a good idea.
Cheers,
Andy
¹ 41.1% of customer VMs, according to our database.
--
https://bitfolk.com/ -- No-nonsense VPS hosting
31 Oct
31 Oct
7:25 p.m.
Thanks a lot for this very useful info and reminder Andy. I am one of the
shameful few who has still done nothing on this front; however this has
given me enough of a nudge that I am finally switching to 64-bit kernels
right now.
If for some reason you were really desperate for a guinea pig for the new
crossgrader package I might be open to volunteering. Although I would
definitely want to take a snapshot of the whole VPS first for sure!
OTOH if others try crossgrader before me and report good results then I'd
love to hear about them.
On Fri, 30 Oct 2020 at 23:31, Andy Smith <andy(a)bitfolk.com> wrote:
Hello,
Perhaps of interest to those of you still on 32-bit installs¹,
Debian now has a "crossgrader" package that has just had its first
version uploaded to the "unstable" suite:
https://salsa.debian.org/crossgrading-team/debian-crossgrading/
I have used this manual process:
https://wiki.debian.org/CrossGrading
many times to go from i386 to amd64, but it is unsupported and scary
and depending on the exact packages you have installed can be very
tricky. It will ask you to approve actions that may destroy your
system.
I haven't yet had chance to try "crossgrader" myself yet, but I will
try it next time I have to do this. I would be interested in reading
your experiences of using it.
I gather that it would be wise to fully upgrade to the latest stable
release (buster) on i386 before trying to crossgrade to amd64,
either by this method or manually.
For those keen to switch to 64-bit, much of the benefits can be
obtained without most of the risk by only changing your kernel to
the amd64 architecture. After following the wiki article above to
the end of the "Install a kernel that supports both architectures in
userland" section, you would:
1. Connect to Xen Shell and use the "console" command if not already
in it.
2. Halt your VPS.
3. Use the Xen Shell "arch" command to switch to x86-64 bootloader.
4. Use the Xen Shell "boot" command to boot it.
5. When your own grub menu appears, select the amd64 kernel that is
listed, not the i686 one.
Provided everything seems to work okay you can then remove the i686
kernel packages, and the system will keep the -amd64 kernel packages
up to date. Your VPS is then a 64-bit one running a 64-bit kernel
but with almost entirely 32-bit userland.
Changing over the 32-bit userland by either the crossgrader package
or manually is where most of the complexity lies.
For context as to why you might want to switch away from 32-bit:
- The next major Xen release will remove 32-bit PV support. We'll
switch to PVH mode before then to allow remaining 32-bit guests to
still run.
- At the recent Xen Developer summit it was stated that "anyone
still running 32-bit PV is setting fire to 30% of their CPU".
- All manner of 32-bit-specific fixes, including security, are being
delayed and overlooked in the upstream Linux kernel, so switching
away from running an i686 kernel would be a good idea.
Cheers,
Andy
¹ 41.1% of customer VMs, according to our database.
--
https://bitfolk.com/ -- No-nonsense VPS hosting
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Andy Smith