CentOS 7.4 USB media - Always fails media check

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jvroig
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CentOS 7.4 USB media - Always fails media check

Postby jvroig » 2017/10/18 00:28:52

Hi,

I'm encountering this strange problem where the USB media (Centos 7.4 (1708)) always fails the media check.

I've verified that the sha256 sum of my downloaded iso is correct.

I've also had several (a couple dozen) successful installs with that ISO img, loaded into 5 different flashdisks.

I don't think I even really tried testing the install media before (the default prompt when booting through USB installer), but I did yesterday when one install failed. Turns out, none of the USB installers I had pass the media test - most of them can't even seem to start it properly (stops at 4.8%, error message says something like it can't start the verification process).

Is this a known issue? I've tried the media check in 3 different computers, just to be certain it isn't just a particular computer that fails my USB installers.

Then I formatted those flashdisks, and reloaded the ISO. They all still failed. Then I got 4 different (new) flashdisks, loaded the ISO (re-checked the sha256 sum, just to be sure, before burning), and they all still failed the media test.

I don't know what's happening here. Any ideas?

hunter86_bg
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Re: CentOS 7.4 USB media - Always fails media check

Postby hunter86_bg » 2017/10/18 04:12:24

The only recommended way to make your USB is via 'win32imager' (not sure if i spelled it correctly) and 'dd'.
In some previous versions there was a bug about the checksumming but I'm not sure this is the case.

jvroig
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Re: CentOS 7.4 USB media - Always fails media check

Postby jvroig » 2017/10/18 05:41:19

Hi Hunter, thanks for dropping by.

I don't use Windows to create my USB installers, so we can rule that out (I rarely use Windows).

I simply use the 'Disks' application (gnome-disk-utility). Basically, 'Disks' -> Burger Menu -> 'Restore Disk Image'. I'm pretty sure it just uses dd.

Anyway, so I just used 4 "defective" USB installers again (i.e., they all consistently fail their built-in media test), and again the installation had no problems. If I can't rely on the built-in media test, then it sort of hinders my ability to rule out certain things when I do encounter problems - e.g., ruling out possibility of installer corruption when 1 install attempt in a different machine fails, out of dozens of previous successful installs in a different set of machines.

If anyone can say for sure there is a definite bug that triggers in certain conditions, that'd be great so at least I can have peace of mind to just ignore the media test. I'll also see if I can post screenshots of the errors encountered during the test media process, perhaps there's a clue there that some of you can use. Thanks!

jvroig
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Re: CentOS 7.4 USB media - Always fails media check

Postby jvroig » 2017/10/20 05:46:27

Here are the only screengrabs I could find to show what happens when the media check option is chosen. They aren't the best quality, and it looks too far into the process to actually see the immediate response from the media test, but it's all I have right now. Maybe some of you can figure out some clues from them. Thanks!
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TrevorH
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Re: CentOS 7.4 USB media - Always fails media check

Postby TrevorH » 2017/10/20 08:41:34

That's a hardware error - your drive is getting i/o errors all over the place.
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jvroig
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Re: CentOS 7.4 USB media - Always fails media check

Postby jvroig » 2017/10/28 03:00:25

Yeah, if I had a screenshot of the more immediate errors, it'd be more helpful than the generic I/O errors there.

I think I have found a pattern though - it only happens for UEFI-only machines.

I just tested now, and in machines that still have the old BIOS, it actually works with no problems - same flashdisks.

I'll see if I can have time next week to specifically gather screenshots early in the process for UEFI machines, so we can actually get solid data.

Thanks!

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TrevorH
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Re: CentOS 7.4 USB media - Always fails media check

Postby TrevorH » 2017/10/28 09:58:58

The iso images use a different code path on UEFI machines than they do on legacy BIOS machines and many utilities corrupt the UEFI data when creating a USB stick. I'd suggest your first step should be to rewrite the stick using plain ordinary dd as that always works.
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jvroig
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Re: CentOS 7.4 USB media - Always fails media check

Postby jvroig » 2017/10/29 00:04:51

Hi Trevor,

Alright, that's cool to know. I'm pretty sure the Disks utility simply call dd anyway, but removing complexity and being 100% certain is the best idea going forward (scientific method and all), so I'll make sure and go ahead and try creating the flashdisks using the tried and true, classic dd methid.

I'd note that the flashdisks install correctly on servers - in fact, for the last month they've been used pretty much daily. It's really just the media test that fails if I choose to run it.

Anyway, will get back to this thread when I have more results on hand, hopefully with screenshots!

jvroig
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Re: CentOS 7.4 USB media - Always fails media check

Postby jvroig » 2017/11/02 12:03:10

This is probably my last update, I consider the case closed.

1.) I made a new USB flashdisk installer, using plain old dd, using the CentOS 7.4 image.
2.) Tried media test at boot prompt on UEFI machines. Fails all the time, ends up with the IO errors / SQUASHFS errors as from previous screenshots.
3.) If I just skip the media test by choosing the option above it ("Install..." instead of the default "Test and install..." option), everything's fine.
4.) Tried the same flashdisk on a non-UEFI machine. It repeatedly passes the media test and ends up on the installation screen. I repeat the process 4 times to be sure. Flawless.

At the same time:
1.) I have a USB installer at home that already passed repeatedly in my non-UEFI machine.
2.) I brought that installer to work, so I can see if it passes on my UEFI machines, since I already know it passed repeatedly on non-UEFI
3.) It just keeps getting errors on the UEFI machines.

At this point, I'm pretty much satisfied. Through dd or Disks, the installers work, they pass media test on non-UEFI, but they just can't pass on UEFI-only machines (or at least, the specific boards that I have, maybe).

I'm good here. If no one has anything to add, I consider this issue closed, as I'm satisfied I can just peaceably ignore my UEFI test failures.

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TrevorH
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Re: CentOS 7.4 USB media - Always fails media check

Postby TrevorH » 2017/11/02 13:49:14

I'd say this is worthy of a bug report to bugs.centos.org
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