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Old 12-16-2008, 06:00 AM   #1
storkus
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Kernel<->GLIBC dependency question


Apologies if this has been asked elsewhere or (especially) if covered by a FAQ, but I have yet to find the answer after all these years.

It is widely hinted in distro changelogs and and in the kernel docs that there are major dependencies between the system libraries and the particular kernel version they were compiled under, but I've never seen them actually spelled out. Is there a document somewhere that explains what they are?

Could they be the reason why my machine seems to become unstable with age (like a winblows machine!) until I do a clean distro install again?

Thanks, Mike
 
Old 12-16-2008, 08:10 AM   #2
cladisch
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Quote:
It is widely hinted in distro changelogs and and in the kernel docs that there are major dependencies between the system libraries and the particular kernel version they were compiled under, but I've never seen them actually spelled out. Is there a document somewhere that explains what they are?
There is no such document.

When a new kernel has new features that cannot be handled with the previous API, you need to use new libraries. This does not affect any 'old' functionality.

Quote:
Could they be the reason why my machine seems to become unstable with age (like a winblows machine!) until I do a clean distro install again?
No.

Reasons for that could be more installed stuff, more configuration changes, disk fragmentation, hardware errors, etc.
 
Old 12-16-2008, 09:13 AM   #3
storkus
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Ok, then let me ask this: why is it every time a distro, in the "current" stage, upgrades the kernel, it immediately recompiles all major libraries along with it?

For example, you see in the changelog something like this:

Kernel: upgraded to 2.6.27.x
Glibc: recompiled against kernel 2.6.27.x
...

along with several other libraries.

Thanks again, Mike

Last edited by storkus; 12-16-2008 at 09:17 AM.
 
Old 12-16-2008, 10:28 AM   #4
cladisch
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why is it every time a distro, in the "current" stage, upgrades the kernel, it immediately recompiles all major libraries along with it?
This happens only for libraries that use kernel headers.

Recompilation makes sure that any changes or bug fixes in the kernel headers are picked up.
If those parts of the headers that are actually used by a library haven't changed, the recompilation was pointless, but looking through the changelog for changes that might affect a library is so tedious and error prone that it's better to recompile, just to be safe.
 
Old 12-17-2008, 02:39 AM   #5
storkus
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Originally Posted by cladisch View Post
This happens only for libraries that use kernel headers.

Recompilation makes sure that any changes or bug fixes in the kernel headers are picked up.
If those parts of the headers that are actually used by a library haven't changed, the recompilation was pointless, but looking through the changelog for changes that might affect a library is so tedious and error prone that it's better to recompile, just to be safe.
But that gets back to what I've been trying to ask: if I go about compiling a new kernel every time a patch comes out, but don't touch any libraries, could this result in increasing system instability over time, especially with device drivers?

Example: Slackware/SlamD64 12.1 came with kernel 2.6.24.?, but I'm currently running 2.6.27.8. A lot has changed over that time, and I'm now running V4L/DVB drivers, which change a LOT of course, and this is coincidentally also the same time that the worst of the instability started. (Although I think the changes made to the USB core as of 2.6.27 may be to blame for much of it.)

Thanks again for putting up with this, I just really want to nail this one down once and for all.

Mike
 
Old 12-17-2008, 03:33 AM   #6
cladisch
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if I go about compiling a new kernel every time a patch comes out, but don't touch any libraries, could this result in increasing system instability over time, especially with device drivers?
No, newer kernels always take care to stay backwards compatible in their userspace interface.

It is, of course, possible that a new kernel introduces new bugs.
Furthermore, it can expose a previously unknown bug in an 'old' library because it has new functionality that, when you try to use it, uses previously unused parts of that library.
 
  


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