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Dominique_71
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Joined: 17 Aug 2005
Posts: 1922
Location: Switzerland (Romandie)
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 Posted: Fri Jun 10, 2022 12:07 pm Post subject: Kernel downgrade to amd64 into an ~amd64 system |
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Into an ~amd64 system, I want to use stable kernels. For that, I added the following into /etc/portage/package.accept_keywords:
| Code: | sys-kernel/gentoo-sources -~amd64
sys-kernel/linux-headers -~amd64
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and in /etc/portage/package.mask/sys-kernel/rt-sources:
| Code: | | >=sys-kernel/rt-sources-5.16 |
Making a system update, portage tell me:
| Code: | # emerge --deep --newuse --update --with-bdeps=y -a @world
These are the packages that would be merged, in order:
Calculating dependencies... done!
[ebuild UD ] sys-kernel/linux-headers-5.15-r3::gentoo [5.18-r1::gentoo] USE="-headers-only (-experimental-loong%)" 119,058 KiB
[ebuild NS ] sys-kernel/gentoo-sources-5.15.41:5.15.41::gentoo [5.17.0:5.17.0::gentoo, 5.18.2:5.18.2::gentoo] USE="-build -experimental -symlink" 1,788 KiB
[ebuild NS ] sys-kernel/rt-sources-5.15.29_p37:5.15.29_p37::gentoo [5.16.2_p19:5.16.2_p19::gentoo] USE="-build -deblob -symlink" 1,278 KiB
[ebuild rR ] sci-visualization/gnuplot-5.4.3::gentoo USE="X cairo gd qt5 readline wxwidgets (-aqua) -bitmap -doc -examples -ggi -latex -libcaca -libcerf -lua -regis" LUA_SINGLE_TARGET="lua5-1 -lua5-3 -lua5-4" 0 KiB
Total: 4 packages (1 downgrade, 2 in new slots, 1 reinstall), Size of downloads: 122,124 KiB
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Is it safe to do that like that, or is it some changes or additional steps that must be done? |
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pietinger
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Joined: 17 Oct 2006
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Location: Bavaria
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Dominique_71
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Joined: 17 Aug 2005
Posts: 1922
Location: Switzerland (Romandie)
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| Posted: Fri Jun 10, 2022 1:22 pm Post subject: |
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Thanks, I moved the settings for the gentoo-sources and linux-headers into package.mask in order to get the latest LTS.
Another concern I have, as I am downgrading the kernels, is the system consistency. I have the following notes:
| Quote: | From Linus:
Kernels are backward compatible, which imply the linux-headers must be updated
before glibc (which is not backward compatible).
From glibc FAQ:
glibc run fine on kernels older than the linux headers. With kernels newer than
glibc, glibc can't use new kernel features. |
From the glibc FAQ, it should be fine, but the installed glibc was compiled against a never version of the linux-headers than the one resulting of this downgrade. From linus, the glibc is not backward compatible. I find that a little bit confusing to me in that case. |
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pietinger
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Joined: 17 Oct 2006
Posts: 5372
Location: Bavaria
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| Posted: Fri Jun 10, 2022 2:00 pm Post subject: |
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Yes, there is even a recommendation to use always the newest linux-headers. Because when you compile glibc you already have all new kernel functions in glibc. If some applications try to use it AND you dont have the newest kernel for it, the application must be able to handle this ... but ... I am an old man, and I learned I should have the correspondent header-files. In reality there were only very rare situations where you had problems with a non-correspondent header for linux kernel.
So, yes you could use your sys-kernel/linux-headers-5.18 furthermore and dont let them downgrade. |
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Hu
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Joined: 06 Mar 2007
Posts: 23082
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| Posted: Fri Jun 10, 2022 3:08 pm Post subject: |
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| Downgrading linux-headers is meaningless unless you subsequently rebuild glibc. The headers affect how glibc is built, but not how it runs. In principle, new glibc should work on an older kernel, within some limits that are likely so generous as to be irrelevant for you. |
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Dominique_71
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Joined: 17 Aug 2005
Posts: 1922
Location: Switzerland (Romandie)
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| Posted: Fri Jun 10, 2022 3:28 pm Post subject: |
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| OK. Do you know, when compiling the gentoo-sources, if gentoo is using the headers from the kernel-headers package or from the kernel itself? |
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NeddySeagoon
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Joined: 05 Jul 2003
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| Posted: Fri Jun 10, 2022 10:48 pm Post subject: |
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Dominique_71,
Kernel builds use the headers in the kernel, as do out of tree kernel modules.
Userland uses the separate headers package.
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Regards,
NeddySeagoon
Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail. |
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Dominique_71
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Joined: 17 Aug 2005
Posts: 1922
Location: Switzerland (Romandie)
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| Posted: Sat Jun 11, 2022 9:49 am Post subject: |
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Thank you all,
I will downgrade the kernel-headers and test it with the gentoo-sources a few days. If everything is OK, I think so, I will test it with the rt-sources. |
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figueroa
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Joined: 14 Aug 2005
Posts: 3007
Location: Edge of marsh USA
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| Posted: Sun Jun 12, 2022 2:58 am Post subject: |
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You shouldn't need to downgrade the headers.
Added: I'm currently using linux-headers-5.15-r3 with gentoo-sources-5.10.117.
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Andy Figueroa
hp pavilion hpe h8-1260t/2AB5; spinning rust x3
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amd64/23.0/split-usr/desktop (stable), OpenRC, -systemd -pulseaudio -uefi |
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