Re: multiarch status update

[Gabor Gombas <gombasg@sztaki.hu>]

On Wed, May 17, 2006 at 12:14:24AM +0200, Goswin von Brederlow wrote:

> Wait a second. How do you create the dir when the file already exists?

There was quite some talk on linux-kernel about
'every-file-is-a-directory' approaches when Reiserfs 4 was released.
Some said they'd like to see this feature in other file systems if only
someone got the nerve to design & implement the needed VFS extensions.

> Say I have /usr/bin/firefox/i486 and /usr/bin/firefox/x86_64. Which
> one should be the default? Where/how do I set the default?

This is just theory, but if you implement the
'every-file-is-a-directory' concept with extended attributes then
- /usr/bin/firefox is just a stub file containing a magic cookie
- the per-architecture binaries are stored as EAs
- there can be a 'default' EA pointing to the default architecture, so
  you can set the default separately for every binary
- a binfmt_misc helper should be created that intercepts the magic
  cookie in the stub file and loads the binary from the appropriate EA

This way running /usr/bin/firefox gives you the defalt arch, and
/usr/bin/firefox/$ARCH (or /usr/bin/firefox@$ARCH or whatever syntax you
define for accessing the EAs) gives you the binary for the specific arch.

> I never use flash so I want the x86_64 default. But userB always uses
> flash and wants i486. How do you set that up per user?

This problem already exists with alternatives regardless of multiarch.
The sysadmin sets up JDK-1.5 as default using the alternatives system
but userB always uses JDK-1.4. How do you set that up per user?

alias firefox=/usr/bin/firefox/i486 works just fine for userB.

> Multiarch (so far) does not allow the same path/file in 2 packages
> (with the exception of /usr/share/doc/ files)

Hmm. How do you want to handle one-arch-only binNMUs? binNMUs change
changelog.Debian.gz, so
- you can't upgrade just the architecture that was binNMUed without
  changelog.Debian.gz becoming invalid for the other arches
- there will be no new version for the other arches so you can't just
  wait till the versions are in sync

Gabor

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     MTA SZTAKI Computer and Automation Research Institute
                Hungarian Academy of Sciences
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