Ubuntu: Install Ubuntu from ISO… cannot install grub


I have a broken Ubuntu 14.04 LTS system (i.e., it does not boot) in sda6 (in sda3, extended), so I am booting from the 14.04 LTS installation CD. sda6 is readable, and I can mount sda6, but I cannot boot. This additional info on the cause of problems may help.

I mean to install Ubuntu 16.04.1 LTS directly from iso, into a new partition sda1 (primary). I have placed the iso file in a directory in an ext4 partition sda4 (primary). I followed instructions in the accepted answer of Install Ubuntu from ISO image directly from hard disk of a system running Linux? . When I try to

sudo update-grub

I get

/usr/bin/grub-probe: error: failed to get canonical path of '/cow'.

All references to this problem (Failed to get canonical path of /cow , e.g.) indicate that one should identify the grub partition and perform a couple of steps. But I do not know if I have such partition, nor how to identify it. I have one other partition sda2.

I guess anything I do in / is volatile, and I can only have persistent stuff under mounted sda partitions.

Here is the output of fdisk -l /dev/sda

Disk /dev/sda: 750.2 GB, 750156374016 bytes  255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors  Units = sectors of 1 * 512 = 512 bytes  Sector size (logical/physical): 512 bytes / 4096 bytes  I/O size (minimum/optimal): 4096 bytes / 4096 bytes  Disk identifier: 0x7fa54200       Device Boot      Start         End      Blocks   Id  System  /dev/sda1       976564224  1078964223    51200000   83  Linux  /dev/sda2   *        2048     1955839      976896   83  Linux  /dev/sda3         1957886   976564223   487303169    5  Extended  Partition 3 does not start on physical sector boundary.  /dev/sda4      1078964224  1465147391   193091584   83  Linux  /dev/sda5         1957888    66406399    32224256   82  Linux swap / Solaris  /dev/sda6        66408448   976564223   455077888   83  Linux    Partition table entries are not in disk order  

Gparted is shown below

enter image description here


I needed to modify grub configuration to boot from an iso image from HD since BIOS changing to USB boot was password locked, so a linux live was not viable.

I managed to boot from iso by typing what was needed in the grub editor at boot time.

So, technically, I solved my problem without answering this question, and I still do not know the answer.

But installation failed anyway. I then got a password for the BIOS, change boot to USB, used a linux live and installed 16.04 with no problem.

Conclusion: the results of an installation attempt from iso on HD was different than from USB, even if they should be the same (failure vs. success).

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