Ubuntu 13.04 To Look At XZ-Compressed Packages

[AJenbo]

I just wish they could do this for live cd so we could keep below the 704MB limit.

[allquixotic]

This move does make sense for Ubuntu, since they don't even support Pentium M anymore.

But it's more about Debian, I think they still support 486?

If anyone but a museum still supports 486, they need to have their heads examined. The number of people who use a 486 (or even a 586) is so low that the userbase of a package that I created specifically for my own needs called "allquixotics-tools" would have a larger user base than a distro would have 486 users.

[Vorzard]

On 486-class hw, it takes over 10x as long to decompress vs gz, while also using 32x the RAM or more (depends on dictionary size). I've also had xz -9 OOM occasionally trying to compress a big tarball, the cpu + ram requirements for compression are just ridiculous (on a comp with 8gb ram no less).

Ubuntu is not suitable for 80486 machines, not even for embedded systems based on a 80486 processor.

Also from Ubuntu 10.10 i486 along with i586 and i686 (without cmov) is not supported anymore.

The default preset for xz is 6, when you use higher you should take compressor and decompressor memory usage into account.

The xz is offering better compression ratio (with network transmission and hard drives you gain speed with the smaller file size) and designed to support parallelization.

Altough xz-utils is single-threaded and produce a big block of compressed data instead of smaller blocks (no random access).

[curaga]

If anyone but a museum still supports 486, they need to have their heads examined. The number of people who use a 486 (or even a 586) is so low that the userbase of a package that I created specifically for my own needs called "allquixotics-tools" would have a larger user base than a distro would have 486 users.

You'd be surprised

It's not so much Intel 486 from 15 years ago, it's the embedded 486 variants that run at 1 GHz that have some userbase.

[chithanh]

xz (lzma) is an ok choice, but it is by far not the best compressor. The only advantage is that it is already installed by default almost everywhere. If decompression speed is important, then e.g. lzham would be more suitable.

http://mattmahoney.net/dc/text.html

[Wilfred]

This. The only question is: what took them so long?
I've been using xz for a while. It's very useful when I have to move large log files over the network, for example. Just replace czf with cJf and you're done!

From the man page of a recent version of tar
--
-a, --auto-compress
use archive suffix to determine the compression program
--

[bug77]

From the man page of a recent version of tar
--
-a, --auto-compress
use archive suffix to determine the compression program
--

Thanks for the tip. I have read the help countless times and somehow I still managed to miss that. Or maybe it was introduced after I finally managed to remember the syntax

@chithanh Indeed, choosing such a compressor is driven mostly by omnipresence. That and it must exhibit low to medium CPU usage. Everything else is just gravy.

[Dan555a]

I also hope they adapt delta diff from fedora/rpm.

[Ibidem]

1. On FDN, I saw _talk_ about Debian moving from i486+ to i586+ (within the last ~year).
The post I saw said that the developers were considering it, but wanted comments from anyone who might be affected.

2. As curaga mentions, there are newer CPUs that are i486-level ISA but much faster than an i486.
There are also the CPUs that have some sort of emulation for the Pentium instructions, so they run slower when run in Pentium-compatible mode.
(FYI: when ConnochaetOS got going, some company approached the developer with an offer to sponsor development if they supported i486 CPUs).

3. Ubuntu requires a minimum of 64 MB just to do a text-mode install and more like 256-512 MB to have a working desktop, and has since 8.04 (Hardy Heron). Ubuntu also requires an i686 or better (or AMD64, ARMv7, PowerPC, IA64, or UltraSPARC, with at least Power and perhaps the last 2 being "community supported"), PAE, and so on. The added overhead of xz compression is negligeable for this level of computer. Now, if we were talking about a distro like Debian where you could anticipate someone using it on a Raspberry Pi or something lower like m68k, that might not be true.

4. Delta-debs were proposed and rejected on the grounds that a lot of people skip at least one package release, and also you can't rely on the debs being present locally if they clean the package archive. If you want them, explain to the Ubuntu developers why those aren't a problem once you've read the relevant Brainstorm pages.

[Markore]

I second what szymon_g said:

We actually need to see feature like "delta rpm" have for years.
So "delta debs" will actually save bandwidth, speed up upgrades and make people very much more happy,
then simply changing default compression algorithm.

Change of compression algorithm should be done in respect to future "delta deb" feature,
because we want smarter things and better technology, not only fast big new stupid ones.