Can't Boot Windows after dual-boot installation with Lubuntu

[arius88]

Fred, I really can't tell you how much I appreciate all your assistance here. I'd be lost without you.

I tried entering the first of the commands you suggested:
sudo sfdisk -A2 /dev/sda

and got the following back

sfdisk: invalid option -- `2'

[oldfred]

Sorry this is just an example of the command. You have to replace sda with your drive and 2 with your partition. Probably should have posted this for sdXY. Added space, see below.
sudo sfdisk -A Y /dev/sdX
sudo sfdisk -A 1 /dev/sda

Your Windows boot partition is sda1.
But Boot-Repair copied essential boot files to sda2.
Windows does allow BIOS installs to not have boot partition and have only the one partition, so boot flag can work on either sda1 or should work on sda2.
looks like space between N & partition number is required
https://man7.org/linux/man-pages/man8/sfdisk.8.html
man sfdisk

[arius88]

Okay. So I tried

sudo sfdisk -A 1 /dev/sda

and got

"sfdisk: cannot open 1: no such file or directory"

After reading up on sfdisk a bit, I tried running

sudo sfdisk -V sda

just to check on the partitions
and again it said "sfdisk: cannot open sda: no such file or directory"

Not sure if this is a syntax issue, or if I'm in the wrong directory (if i am, i have no idea what the right directory is or how to get to it), or whether there's something else going on.

sfdisk -l clearly lists all four sda partitions, so obviously it can find the device when it wants to.

sda1
sda2
sda3
sda4

What am I doing wrong?

[oldfred]

You have to use full device. Almost all Linux commands are /dev/sda not just sda

fred@Z170-jammy:~$ sudo sfdisk -V /dev/sda 
/dev/sda:
No errors detected. 
Header version: 1.0 
Using 10 out of 128 partitions. 
A total of 601090579 free sectors is available in 6 segments (the largest is 286.6 GiB).

I rarely use sfdisk. If using command line I use gdisk as I only use gpt partitions.
But normally use gparted as I have gui.

[arius88]

Ah. Got the -V thing to work! No errors detected, so that's good.

But why did "sudo sfdisk -A 1 /dev/sda" yield "no such file or directory"?

[oldfred]

I always install gparted, so have not used the command, but had it in my files.
I suggest gparted as I know it works.

You can use gparted on umounted partitions. But with old MBR, all logical partitions inside the extended partition are seen as mounted if any partition is mounted. So normal suggest is to use live installer. Ubuntu has gparted. Or you can download a gparted live ISO.
I have two drives so install gparted to use on other drive. And with gpt I can add or modify any unmounted partition just not the mounted ones.

[arius88]

Made a GParted live CD, running it now.
Was quickly and easily able to change the boot flag to sda1 by right clicking on the partition and selecting "Manage Flags" and checking the Boot option. Awesome.

HOWEVER

As soon as GParted loaded the GUI or whatever with my partitions displayed, I noticed a warning label on sda1. (The other partitions seem to be fine.) Clicking on it yields the following information:

! Warning:

Unable to detect file system! Possible reasons are:
-The file system is damaged
- The file system is unknown to GParted
-There is no file system available (unformatted)
-The device entry /dev/sda1 is missing

1. Should I be concerned about this, or is it just because it's a Windows partition?
2. What's my next move?

Edited to add: I found this article. Looks useful, but I'm a bit scared to try it. https://www.diskpart.com/articles/gp...-mbr-7201.html. It's advising me to use something called "testdisk." What do you think?

[oldfred]

Testdisk is good for recovering missing partitions. Or perhaps recovery of backup PBR - partition boot sector.

You have sda1, but it does not seem to see it as NTFS.
First you should try chkdsk from a Windows repair disk. If it also gives errors, it may be issue with PBR.
Partition table says NTFS. But Windows NTFS & FAT32 have essential info in the PBR partition boot sector (record). NTFS does have a backup PBR that can be recovered with testdisk or Windows tools.

You want to get to this screen:
http://www.cgsecurity.org/wiki/TestD...ector_recovery
select [Advanced] instead of [Analyze] and select [BackupBS]
[HowTo] Repair the bootsector of a Windows partition - YannBuntu
https://help.ubuntu.com/community/BootSectorFix
http://ubuntuforums.org/showthread.php?t=1926510

Testdisk also can create a new BS, but it used to be the XP type. You then have to run chkdsk from a newer copy of Windows which will convert it to the newer version.

If for example, you installed grub to sda1, it will overwrite the Windows PBR. Testdisk may say it is valid as grub can be in a PBR (but never should be), just not in any Windows formatted partitions.

[arius88]

Always good to hear back from you, Fred.

Ran chkdsk from the Windows 7 install disk. No errors, so I'm guessing the PBR is okay.
Going to take a nap and then see what I can do with Testdisk.

[oldfred]

If PBR - partition boot sector is not seen as NTFS, chkdsk does not run.
Depending on which parameters you used, you may have repaired it.