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METROIDHunter_
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Joined: 14 Mar 2023
Posts: 13
Location: USA
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 Posted: Thu Nov 14, 2024 12:42 am Post subject: QEMU virtiofs chroot: clock skew errors during emerge |
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Greetings everyone,
I have a very strange problem involving Gentoo, QEMU, and virtiofs.
I have set up a QEMU/KVM VM to chroot into a virtiofs mount and compile Gentoo binary packages to serve to my old 32-bit x86 laptops. Right now I'm trying to build binary packages for my clients, but a few important packages are receiving errors from make or gmake:
| Code: | | Clock skew detected. Your build may be incomplete |
or
| Code: | | ERROR: Clock skew detected. File /var/tmp/portage/app-arch/zstd-1.5.6/work/zstd-1.5.6/build/meson-abi_x86_32.x86/meson-private/coredata.dat has a time stamp 0.1444s in the future. |
The clock skew is never much. It's always between 0.1 to 0.6 seconds in the future, in my experience. But these errors prevent the packages from building.
I can see 3 specific packages with this problem - all of them complain that a file's timestamp is less than 1 second in the future, and they refuse to build:
app-arch/lz4
app-arch/zstd
dev-build/cmake
CMake even throws an additional error, which I suspect to be related to the clock skew issue:
| Code: | CMake Error at CMakeLists.txt:93 (message):
The C++ compiler does not support C++11 (e.g. std::unique_ptr). |
Let me clarify my setup a bit further: I have a Gentoo host running a Linux QEMU VM (tested with Alpine and Gentoo, x86 32-bit). The VM is provided a shared filesystem via virtiofs, which serves as the chroot for my binpkg host.
Gentoo Host:
Gentoo Guest VM:
Gentoo binpkg chroot:
While writing this forum post, I had the idea to try building cmake from a chroot directly from my host, without using the VM... and it emerged successfully. Something about my virtualization layer is causing the problem.
Also, the Gentoo VM is able to build the aforementioned packages without issue on its own root filesystem; but when I use my Gentoo (or Alpine) VM to chroot into my virtiofs filesystem (where my Gentoo binpkg host lies), then I have problems.
Does anyone have any ideas? I feel certain that virtiofs is involved in this problem, but I'm hoping somebody can help point me in the right direction.
Thank you for your attention 
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METROIDHunter_
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Joined: 14 Mar 2023
Posts: 13
Location: USA
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| Posted: Sun Jan 26, 2025 9:31 pm Post subject: |
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A few months later and I've found a solution. Apparently the options I passed to 'mount' were causing a problem. Originally I mounted my virtiofs shares with:
| Code: | | rw,noatime,nodiratime |
I changed that to simply:
And all my problems are gone.
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METROIDHunter_
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Joined: 14 Mar 2023
Posts: 13
Location: USA
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| Posted: Sat Feb 01, 2025 11:02 pm Post subject: |
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Once again I'm faced with clock skew errors from Meson. Looks like my previous "solution" was short-lived.
But I just found a really simple & easy solution... within the chroot, I am now mounting the portage TMPDIR (/var/tmp/portage) as a tmpfs, so the software building is no longer happening on a virtiofs volume.
https://wiki.gentoo.org/wiki/Portage_TMPDIR_on_tmpfs
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