headers_install: good thing or ! ?

[pappy_mcfae]

I was wondering what the general consensus is about installing headers when you compile a new kernel. According the folks at the Slackware forum, entering the command "make headers_install" is a bad thing...and will reduce one's computer to smoldering ashes. Ok, perhaps it's not that bad, but I was warned of all manner of evil that was sure to befall my system just by thinking the command near it.

Curiously, I was never given a time schedule when the destruction of my system was supposed to happen. That particular Slackware install ran from the time that Slack-12 was released (June, 2007) until I decided to kick Slackware to the curb in favor of Gentoo. That was about a week ago. One of the first things I did was compile a new, compact kernel...and install the headers from it.

In the lifetime of that install, I never had one single problem. Not one executable failed. Not the pre-compiled ones that come on the disk, and not the additional stuff I wound up having to compile because Slackware didn't have a dedicated package. I never had one problem with the system, other than the attendant miseries that come with Slackware 12.

I was told issuing that command would lead to all manner of problems, and that I could do it if I recompiled glibc. Well, I couldn't help but notice that when I did the emerge --emptytree system on the machines on which I have installed Gentoo that glibc gets recompiled. It sure didn't seem as frightening as it was painted. If this happens, am I wrong in thinking that make headers_install isn't the bogeyman I've been lead to believe that it is?

I really would like to know from a group of people who would be in a position to really know, one way or the other.

Thanks for your time and consideration.

Blessed be!
Pappy

[Sadako]

It's not a good idea.

The headers in gentoo are installed by the sys-kernel/linux-headers package, and these are the include files everything else is built against, so they should not be changed/updated at random.

From the linux-headers ebuild;

[Dominique_71]

I was not aware of the "make headers_install". I done a search but found almost nothing in the forum about linux-headers against "make headers_install". And I find that this is a very interesting issue.

With google, I find that the LSF is using "make headers_install". Gentoo is using a different way (linux-headers), but it must be possible to switch. The LSF is installing the kernel headers with the toolchain creation: Installation of Linux-Headers:

[pappy_mcfae]

OK, well, I did an emerge --sync followed by a emerge --newuse --update world, and that installed new kernel headers on the machine in question, which is currently running vanilla-sources-2.6.23.14. I believe it was originally built upon gentoo-sources-2.6.19.r-something... (I dumped that kernel right after I finished the emerge --emptytree --system after the initial install).

Since the new headers were installed, and glibc wasn't on the list of packages to be updated, would it be a wise idea to reemerge glibc, then follow that with a complete reinstall of everything? Somehow, I get the feeling that's an option I might want to consider. Is this the case?

Blessed be!
Pappy
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[schachti]

[pappy_mcfae]

Thanks so much. I am emerging glibc even as I type this.

Blessed be!
Pappy
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[schachti]

If you do that, keep in mind to also use a recent kernel (the safest way is to keep the kernel version and the version of linux-headers used to compile glibc in sync). According to what I have read in the forums, it's ok to use a recent kernel together with a glibc that is compiled using older header files - however, some newer kernel features might not work then (but the system will work flawlessly). If, on the other hand, the kernel is older than the linux-headers package used for compiling glibc, you might run into trouble.

In one other thread, someone wrote that after recompiling glibc, he got strange errors - the problem was solved by recompiling the kernel (after re-emerging glibc and rebooting). So if you system behaves strange after re-emerging glibc and rebooting, try to recompile your kernel.

So as a conclusion from some threads in the forum, I always do it this way:

* keep the kernel and the linux-headers in sync (if the kernel is 2.6.23-rX, also use linux-headers 2.6.23)
* after updating linux-headers, re-emerge glibc, reboot, and rebuild the new (matching) kernel

This might not be necessary, however, it should be safe.
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[pappy_mcfae]