My linux mint installation is broken because it is old.
The hdd has four partitions one has linux mint 16 on it. One had ubuntu on it and one has debian on it.

I want to install mint 17.2 on the ubuntu partition.

I tried creating a bootable usb stick but my bios seems old and doesnt boot from gpt partition using usb sticks.

I tried creating a bootable live dvd and it worked but it refused to install saying the dvd drive or dvd is broken. It said installation crashed and I tried a new dvd and a new dvd drive it didn't work.

I downloaded the linux mint 17.2 iso and created a grub2 entry for it and it didn't work.
Next I tried using grub2 command line to boot from the ISO and it worked but I wasn't able to install because the iso was on the hdd and the hdd required to be unmounted before it can be installed. catch 22.

So I copied the mint 17.2 iso to usb stick and I want to boot the iso from the grub2 command line just using the usb instead of the hdd.
Here's what I tried.
grub> loopback loop (hd1,msdos1)/mint17.iso
grub> linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=(hd1,msdos1)/mint17.iso noeject noprompt
grub> initrd (loop)/casper/initrd.lz
grub> boot

The thing is stopping after
(initramfs) /scripts/casper-premount/20iso_scan: line 46: cant open /dev/sr0 no medium found
and it is not even giving the live dvd graphical screen.
The iso-scan/filename is wrong I think. How to make this work. I am running out of options to install mint 17.

Put the entry below in the grub.cfg file of whichever system you are using to boot. Save the change, do not update grub, just reboot and select the option.

You need the exact name of the iso file on the loopback and linux lines. That should work if the iso is on sdb1.

It's not the drive but the partition you want to install to.

It worked. It booted into the iso but I am not able to install.

It says:
The installer needs to commit changes to partition tables, but cannot do so because partitions on the following mount points could not be unmounted:
/isodevice
Please close any applications using these mount points
Would you like the installer to try to unmount these partitions again?
[Go Back] [Continue]
If I click go back or continue nothing happens. The x button on the dialog doesn't work either.

As far as I know I didn't change any partition table info. I left it as it is. Cant it just leave the partition table alone and write the files into the partition? Why is unmounting even necessary? Why is partition table access even necessary? I am still able to boot into the linux mint 16 partition. So there should be no reason for the installer to meddle with the partition info. Anyway I have booted into the USB why is not able to unmount the hdd?

df -m says
/dev/sda5 is mapped to /isodevice
I dont see any other partitions when I boot from usb.
Is there a manual command line way to install or just copy the required files into the ubuntu partion to make it mint 17?

When you assign a drive mapping either in fstab or grub.cfg, use your device's UUID rather than the device node name if you use a removeable device as the boot drive.

Had the same problem when I installed Mint. Open a terminal and run: ls / You should see a directory named isodevice. Trying to manually unmount did not work for me either. Close the Mint installer and open the /etc/mtab file: sudo gedit /etc/mtab You will have to check as I'm not sure if you have gedit, if not replace gedit with the name of your text editor. You should see a line similar to the one below:

Comment it out by putting a hash mark at the beginning of that line, save the file and start the installer again. This worked for me and I was able to finish the install booting the iso directly to install Mint. I don't know why this happens.

you might be able to boot the usb from grub command line with something like this:
to find the hd? of the usb stick then the following assuming the usb is hd1
using the grub boot menu on the usb as an example.

I had to do this to get a usb to boot on my laptop that was gpt formated.

See post #3, he said the suggested boot entry worked. His problem now is with the installer and I've seen this same thing with several releases of Mint as well as other Ubuntu's. In the initial post he indicates he has the iso on the flash drive which, unless he changed that, is how he booted and got the current error.

My suggested was a way to boot the bootable usb stick with the grub installed on the hard drive, not for booting the iso file.

I expect your method would work but, based on the quote below from the initial post, I believe he just has the iso file copied to the flash drive and doesn't have a bootable flash created with dd, unetbootin or similar software.

I believe the op first tried a bootable usb, then a live dvd, then booting the iso file.
@ the op did you do a md5sum check on the iso to verify the iso file is good. Bad downloads to occur every once in awhile.

I tried editing the /etc/mtab file but vi would not allow me to save it saying cannot open the file for writing.
The /dev/sda5 is mounted on /isodevice before I start the installer. I think because the grub is loaded from the partition.

This worked. I was able to install.

Thanks for clarifying otherwise I would have missed the subtle distinction of your solution.

Now I have another problem. Mint 17 is stating that it is running in software rendering mode.

Cinnamon is running without video hardware acceleration and could be a problem with your drivers.
I have a dual 24" monitor setup. How to fix this? (Should I open a new thread for this issue?)

Thank you all for your help. I had been struggling to install mint 17 for a month now.

It would be better to start another thread with the hardware specs.

Actually, /isodevice is the mount point for the iso. The example I posted above was having a Mint iso file on a hard drive partition, sda5. If you have the iso file on a flash drive, it would be something like sdb1 or sdc1, depending upon the drives attached.

I also, out of curiosity, booted a Mint iso and tried to edit the /etc/mtab file with vi and was able to do so and save changes so I'm not sure what happened in your case. I started the installer and got the message about changing the partition table but in this case was able to select Go Back. I didn't see the message about /isodevice being a problem although I have seen that previously with Mint and other Ubuntus. No idea what causes it.

You got it working and that's all that counts.