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
Best Answer
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).