dual booting w windows 10 -now linux is missing

[tmm]

Hi
Have had an older HP workstation that was in W10, and it was converted to a dual booter a couple yrs ago (Centos 7) -(also, not by me, and my smart friend is out of the country now). Would always boot into Centos7 unless one was fast w up/down arrows. -BTW, each system was set to a separate disk, and to be honest, windows hadn't been up and running on it for more than a year!

Seems the clock battery died and I got an error message recently. Since then, it only sees windows and boots into that automatically... -The clock date and time were wrong, but I added a new CRx battery and set the time. No longer do I get that error message, but still no boot sector , -seems to just notice Windows now. Also, btw, I think this machine is old enough it's likely not UEFI, but strictly BIOS, although if I hit the delete key long enough, it will let me lick the drive to boot from (disk only sees windows, as we'd figure).
Using google search, I used the windows command prompt to add boot mgr, -now looks like the older booting, but only choice is windows 10.

Any help would be appreciated! -I'm a pretty good Linux user w some OK IT skills, but this is WAYYY beyond me. Don't have a clue as to what GRUB is, etc.

Thanks!

[tunk]

You could check the BIOS boot order.
The old setup may have had the linux disk at top,
and the BIOS default may be the windows disk.

[tmm]

Thanks for your reply.
I can get into the HP set-up, which is basically the BIOS.
The BIOS boot order menu only shows the basic boot media (like USB, Hard Drive, etc.).

If I get into this HP Z800's "secondary" booting menu (F8), it DOES show an "OS" boot order menu, but the only one listed there is Windows.
There is a possibility to add another "option" when inside this, but I don't know what to type in there for the linux option to add to this menu (I have CentOS 7.xx installed, hopefully, still).

--> Can anybody clue me in, or am I on the wrong track here?

Thanks a bunch!!

-Note that for some reason, I can't seem to be able to log into this centos site (I get "lucky" maybe 1 out of 100 tries). -So my replies are going to be slowwwww. But I'll be reading this forum question, since I have a link to it

Thanks again for any and all help! -So far my machine is essentially a brick, since I have no reason to go in as a Windows 10 user!

[owl102]

Also, btw, I think this machine is old enough it's likely not UEFI, but strictly BIOS

After booting MS-Windows, hit Windows + R key and start "msinfo32". This application shows you the "BIOS Mode", either "Legacy" or "UEFI".

I suspect it will show "UEFI" and CentOS seems to be gone because the boot entry in UEFI NVRAM got lost because of the dying battery.

Options (UEFI):

• Code: Select all

  bcdedit /set {bootmgr} path \EFI\centos\shim.efi

  (in MS-Windows) will add a CentOS boot entry in the UEFI boot menu. Afterwards the laptop should show you "CentOS" in the boot menu. If you could boot CentOS this way, use "efibootmgr" afterwards to set CentOS as default OS.
• Prepare a rEFInd [1] USB stick and boot this USB stick afterwards. rEFInd should find your CentOS installation so you could boot it. Afterwards use "yum reinstall grub-efi shim" to add a CentOS boot entry and set CentOS as default OS. (Or use "efibootmgr --create --label CentOS --disk /dev/sda1 --loader "\EFI\centos\shim.efi" to create a new CentOS boot entry.)

Options(BIOS/Legacy):

• Prepare a Super Grub2 USB stick and boot it. Super Grub2 should find your CentOS installation so you could boot it. Afterwards do a "fdisk -l" (as root) and post the output here so we (hopefully) could see what the next steps could be.

[1] https://www.rodsbooks.com/refind/
[2] https://www.supergrubdisk.org/

[tmm]

Thanks for your reply!

Unfortunately (I guess), this z800 HP workstation is BIOS Legacy.
1) When I installed the CMOS battery and it insisted on going into Windows 10, I googled and tried this (all in Windows):
"bcdedit /set {bootmgr} displaybootmenu yes" which now gives a "windows"-type boot menu, -and it only sees Windows 10 for my option.

2) msinfo32 gives me a bunch of info, but here, we can see legacy:
BIOS Version/Date Hewlett-Packard 786G5 v03.61, 5/03/2018
SMBIOS Version 2.6
Embedded Controller Version 255.255
BIOS Mode Legacy
BaseBoard Manufacturer Hewlett-Packard
...
Boot Device \Device\HarddiskVolume1
...


3) I did a "blank" bcdedit and got this:
Windows Boot Manager
--------------------
identifier {bootmgr}
device partition=\Device\HarddiskVolume1
description Windows Boot Manager
locale en-US
inherit {globalsettings}
default {current}
resumeobject {dedd8d21-9e34-11eb-b5a8-db94993f49e6}
displayorder {current}
toolsdisplayorder {memdiag}
timeout 30
displaybootmenu Yes --0(my change from a few days ago)

Windows Boot Loader
-------------------
identifier {current}
device partition=C:
path \Windows\system32\winload.exe
description Windows 10
locale en-US
inherit {bootloadersettings}
recoverysequence {dedd8d23-9e34-11eb-b5a8-db94993f49e6}
displaymessageoverride Recovery
recoveryenabled Yes
allowedinmemorysettings 0x15000075
osdevice partition=C:
systemroot \Windows
resumeobject {dedd8d21-9e34-11eb-b5a8-db94993f49e6}
nx OptIn
bootmenupolicy Standard
sos No

4) I'm seeing that the system right now doesn't at least seem to notice the separate Linux disk! (Am wondering if that was where the original boot file was??).
- So I'm concerned that adding this: "bcdedit /set {bootmgr} path \EFI\centos\shim.efi" might overwrite the currently active (windows) boot-up, and leave the machine dead? -Anyway, since it's not UEFI-ready, I guess we don't want to even try that, for sure, for now, at least...

5) I guess the only way to go forward at the moment is to create that super-grub stick? --Is that something that I would ask the PC to boot up with instead of its hard drives?


Thanks again,
TMM

[TrevorH]

I'm seeing that the system right now doesn't at least seem to notice the separate Linux disk!

Are you sure you didn't have the BIOS set to boot from the other disk before?

[owl102]

4) I'm seeing that the system right now doesn't at least seem to notice the separate Linux disk!

I wasn't aware of a 2nd hard disk. In this case I agree with TrevorH, it seems all you need to do is telling your BIOS to boot from the other hard drive.

If you are not sure if the 2nd hard disk is even alive, then you could create a Fedora USB stick, boot from it, and try "sudo fdisk -l" in a Terminal, it will show you the partitioning of all connected hard disks.

- So I'm concerned that adding this: "bcdedit /set {bootmgr} path \EFI\centos\shim.efi" might overwrite the currently active (windows) boot-up, and leave the machine dead?

I don't know, but trying this on a BIOS / Legacy System would not work anyway, so I would not even try it.

5) I guess the only way to go forward at the moment is to create that super-grub stick? --Is that something that I would ask the PC to boot up with instead of its hard drives?

Yes. Afterwards it searches your hard disks for bootable systems and present them all in a boot menu.

[tmm]

Hi

Yes, I wasn't involved with the conversion to dual-booting, and apparently it was a bit tricky for this older PC. Ended up we had to use those old PS2 connectors for both keyboard and mouse for the boot-up to work properly, etc., etc. When booting, a full-screen menu popped up for about 3 seconds, and one could use the arrow keys to move to a windows boot, if you weer fast enough .

1) Also, although the windows disk could be mounted in centos, the windows side couldn't see the linux disk(s), which were originally part of the windows C: drive. -Am now a little concerned that this crash- revert back may have reset the config, and they're no longer really separated.

I'm with you guys - My own suspicion is that I bet it was booting from the unix hard drive before the CMOS battery fail...
-I wasn't smart enough to try to look into the details before the crash

2) All I get in the BIOS boot order is this:
Optical Drive
USB device
Hard Drive
Integrated SATA
ST 1000DM003-1SB102
ST 1000DM003-1SB102
Embedded Ethernet controller
Embedded Ethernet controller (ASF)

-BIOS doesn't seem to see 2 drives?? -Don't know if I could just "pick" the second one of those two identically-named SATA drives???

3) So, "best" way forward?? Do you guys think the best bet would be to make a linux usb stick (like fedora) and explore, -or would that super-grub also be able to see what's partitioned around?? Just a weird thing... If I had to bet, I wouldn't think that the separate linux disk is at all faulty. And fingers crossed that's the case!!

Thanks again
TMM

[Whoever]

There is probably a submenu to pick the specific hard drive to boot from.

[tmm]

this is the whole BIOS menu..

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