Modified system reserved partition but now no boot device found error(code:0xc000021a) on dual boot system(Windows 10 & Ubuntu LTS 18.04)

1

I actually tried to modify the system reserved partition size so that the recent windows update can be installed without error on my hp 15ac122tu machine which is i3 5th gen.

I tried to modify the size using mini partition tool by creating 500mb unallocated space and expanding the system reserved partition with that unallocated space. After the operation, the system falied to boot into any of the operating systems (my machine has ubuntu 18.04 LTS and windows 10 installed using dual boot) .

I think the problem occurred beacuse the modified system reserved partition is not recognized at the time of boot. I tried using diskpart utility, dism, scanning file system using the cmd at advanced options.

I have a discussion on windows forums. Please have a look at it Here. I tried everything they said except the rescue install but the issue still exists. So I'm asking here.

Here's some useful information about my system's disk & partition. Link Here

Note:

(This description is about the images in the above link. Please refer them)

Partition 1- System Reserved(This is the one which I modified)

Partition 2- C drive

Partition 3- Recovery drive

Partition 4- D drive

Partition 5- Swap Space for Ubuntu

Partition 6- Ubuntu Disk

Partition 7- E drive

Please help me to get out of this. Any help will be appreciated.

Thanks in advance :)

Edit:Please consider reading the comments as well to resolve this problem :)

Rohit Babu

Posted 2018-12-18T08:34:11.317

Reputation: 13

Answers

0

You can now only boot from external media, so you should backup your files, possibly take backup images of your important partitions. I would really recommend taking a backup image of the entire disk, in case there is some problem with my theoretical procedure below.

If you can manage to access the contents of the UEFI partition (by assigning it a drive-letter), then take a backup of its contained files as well, because this can save you some time in resetting your dual-boot.

First, delete the resized partition using the tool of your choice.

Create a boot media for Windows of your version and boot into the Command Prompt and enter:

diskpart
List disk
Select disk X       (disk number of the disk)
create partition EFI size=xxx    (your current size in MB)
list partition
select partition N  (the EFI partition)
format quick fs=fat32 label="System"
assign letter=x     (some drive-letter)
exit
bootrec /fixboot
bcdboot C:\Windows /s x: /f ALL

Reboot your computer to see if it is fixed. If this works, you will only be able to boot into Windows.

You may return the previous contents of the UEFI partition and check if you can now dual-boot. Finally unassign the drive-letter in Windows Disk Management.

harrymc

Posted 2018-12-18T08:34:11.317

Reputation: 306 093

I did the same up to the last but one command & succeeded. But the last command is not working. It is showing the list of options available under the bcdboot utility.(I'm doing this in windows 7 live boot ). I have the backup files of the old system reserved partition. Can I use them now?(can copy them to the newly created partition?) – Rohit Babu – 2018-12-20T18:08:18.157

Try it. If it doesn't work, you can always come back here and try to figure out why the bcdboot command is not working (maybe C: is not the right drive-letter, check using the dir command). – harrymc – 2018-12-20T18:56:09.077

Thanks for your reply @harrymc :) . I just found that the letter I assigned to the newly created partition is not available when I booted again into live boot(windows 7) after checking whether I am able to boot to the original windows or not. It failed though :( . But I tried the last command specified by you with slight modification. The windows 7 live boot however failed to recognize the /f option. Hence I removed /f ALL and tried which resulted in the creation of one BOOT folder with several other folders inside it and a file named BOOTMGR(something like this). But the system failed to boot – Rohit Babu – 2018-12-20T19:46:20.953

And one more thing is that I think I lost the BIOS also. Whenever I'm trying to turn on the system, it barely shows nothing but a black screen with no boot device found-- please insert a USB disk or drive and press any key. After that, I tried booting to Kali Linux and I succeeded. But in the past, I'll be getting an automatic repair screen and I am able to select bootdevice form BIOS. But now it is unavailable – Rohit Babu – 2018-12-20T19:48:40.087

Now I pasted the same files which were taken before the creation of new system reserved partition and tried booting. But the problem came back to the start point. Hence I think we need to change some files in the system reserved partition to get this done. But the question is, what files has to be changed in the system reserved partition?? – Rohit Babu – 2018-12-20T20:21:11.663

We have passed the limit to what I can do without hands-on your computer. I think that the best would be to save your files or partitions, reformat the disk and start from scratch. – harrymc – 2018-12-20T20:29:54.540

One more thing I've forgotten specify, after creating a clean efi, I tried bootrec /rebulidbcd. It returned [1] instalation. But when I proceeded to add it to the boot list, it returned "The requested system device cannot be found" – Rohit Babu – 2018-12-20T21:19:06.660

That only creates greater mystery. I suggest to cut the Gordian Knot.

– harrymc – 2018-12-20T21:20:54.403

I reinstalled windows today. Can you tell me how to add the existing Ubuntu to boot details/BCD store? – Rohit Babu – 2018-12-22T11:32:21.690

You could use perhaps EasyBCD for that.

– harrymc – 2018-12-22T12:32:09.573

Actually, I first opted for EasyBcd but it showed some errors & I was unable to add the boot details. Hence I used Boot Repair tool & it installed grub on my machine, added boot files to it. Now my system is working with both operating systems :) (Ubuntu restored, Windows reinstalled ;)) – Rohit Babu – 2018-12-23T09:46:26.197

If my answer has helped solve your problem, consider accepting it (tick the V symbol). – harrymc – 2018-12-23T09:48:32.393

I'll accept the answer but I think your answer is a partial one & it helped me to solve my problem (not completely though) & anyone seeking answer for the same question should consider reading the comments ;) – Rohit Babu – 2018-12-24T14:49:07.993

Asked: 2018-12-18T08:34:11.317

Viewed: 108 times

Active: 2018-12-24T14:52:25.977