Package: lzma
Version: 4.43-14
Severity: wishlist
Hi,
Background, for completeness:
1. The Debian lzma package consists of an lzmp command, which uses the
LZMA SDK functions to handle .lzma files (i.e. lzma_alone format).
2. There is no upstream source for lzmp. The command is maintained in
Debian in debian/patches.
3. Until recently, most other distributions’ lzma command came from
LZMA Utils (which does have an upstream). If the Debian lzma
package is to continue to be maintainable, it should probably be
switched to that.
4. The XZ Utils package provides its own lzma command with the
intention of superseding LZMA Utils.
5. The essential dpkg package depends on the lzma command so it can
handle LZMA-compressed packages. This means that the lzma command
always has to be usable, since a system with LZMA-compressed
third-party packages might be relying on it. If the Debian
archive starts accepting lzma-compressed packages, this will become
even more important.
It would be nice for Debian to gently migrate from lzmp to XZ Utils.
For squeeze, current lzmp users would have the option to continue to
use lzmp or something equally well tested (like lzma from LZMA Utils),
or to switch to xz-lzma. For squeeze+1, if xz-lzma proved reliable
enough in squeeze, it would supersede lzma.
If dpkg did not pre-depend on lzma, this would be easy: just let lzma
and xz-lzma conflict and let the user decide between them. Since lzma
cannot be uninstalled, if lzma and xz-lzma conflict then xz-lzma is
not installable. (See <http://bugs.debian.org/542060>.)
If dpkg were always installed but not essential, this would still be
easy: let lzma and xz-lzma both provide /usr/bin/lzma through the
alternatives mechanism. This would leave lzma without the functionality
dpkg depends on until lzma is configured, which is too late for a
pseudo-essential package.
Where should we go from here?
a. Get dpkg to stop using lzma and use liblzma instead. Since dpkg
is one of the first packages a user upgrades for a new version of
Debian, this makes for an uncomplicated upgrade. lzma should
probably conflict with xz-lzma, as except for during an upgrade
there is no reason at all to have both installed.
I think this is the most sane option.
b. Rename /usr/bin/lzma to /usr/bin/lzmp and ship a symlink from
/usr/bin/lzma to lzmp. Use diversions to make /usr/bin/lzma
point to xz when xz-lzma is installed.
This is messy, but I think it would work. I don’t want to try it.
c. Stop shipping lzmp and rename xz-lzma to lzma.
If a sysadmin was depending on some peculiarity of lzmp, he must
force a downgrade to the older package (but security support through
oldstable would still apply). The lzma source package would still
be needed for lzma-alone and sqlzma.
Thoughts?
Jonathan
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