Problems doing clean install from ISO

Arty Ziff · 10-29-2017, 11:52 PM

Don't let my post count fool you: I'm either still a Newbie or perhaps just an idiot.

So...

I've downloaded my distro of choice (CentOS - I have reasons) in ISO form, and burned it to a DVD.

I've tried restarting the machine with the DVD as the first boot choice, I see activity, but then the system loads the installed OS (which is also CentOS, I wish to do a clean install).

I also tried putting the ISO on a USB hard drive, and changing the boot order to boot from that. I see activity, but again the machine goes on to boot from the installed OS.

Question: If I look at the content of the DVD / hard drive with the ISO on it, what should I see?

Clearly I'm doing something wrong. Perhaps I've downloaded the ISO and burned it incorrectly to the DVD?

And, if the ISO is on the USB hard drive, shouldn't I be able to boot from that if I change the boot order?

What if I extract the ISO files to the USB hard drive? Any better?

michaelk · 10-30-2017, 12:07 AM

If all you see is one file i.e. the ISO itself then you didn't burn as image. If you see a bunch of files then there is a fairly good change you burned as an image. How did you write the ISO to USB drive? If you used the dd command then it should of created a bootable drive.

Did you verify the downloaded ISO using the provided checksums? Assuming that the downloaded ISO is good, burned the DVD as an image and selected the DVD as the first boot device it should work.

Arty Ziff · 10-30-2017, 12:17 AM

Quote:

Originally Posted by michaelk

If all you see is one file i.e. the ISO itself then you didn't burn as image. If you see a bunch of files then there is a fairly good change you burned as an image. How did you write the ISO to USB drive? If you used the dd command then it should of created a bootable drive.

Yes, burned to DVD which now contains a bunch of files. No, didn't use dd command, used a GUI disc burning utility that is a standard package with the CentOS install. For the USB hard drive, simply copied the ISO files to it. Got plenty if DVD's, do you recommend burning again with the dd comand?

Quote:

Originally Posted by michaelk

Did you verify the downloaded ISO using the provided checksums? Assuming that the downloaded ISO is good, burned the DVD as an image and selected the DVD as the first boot device it should work.

Hmmm. No, I did not check the checksum, of course a stupid thing not to do. How would I go about doing that? Never mind, I can Google it. I know where to find the checksums at CentOS.org for what I downloaded.

Thanks for your time!

[EDIT]
OK, bad ISO file:

Code:

mount -t iso9660 /dev/sr0 /mnt

...returns...

Code:

mount: block device /dev/sr0 is write-protected, mounting read-only
mount: wrong fs type, bad option, bad superblock on /dev/sr0,
       missing codepage or helper program, or other error
       (could this be the IDE device where you in fact use
       ide-scsi so that sr0 or sda or so is needed?)
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

But mounting the DVD with a DVD image of *known goodness*, I get this:

Code:

# mount -t iso9660 /dev/sr0 /media/dvd
Cannot create link /etc/mtab~
Perhaps there is a stale lock file?

Hmmm..... It *does* mount, but in read only.

Anyway, the checksums of the ORIGINAL downloaded iso match so it was a burning error that produced an unmountable DVD, but then why can't I boot into the USB hard drive that contains the iso?

michaelk · 10-30-2017, 05:57 AM

ISO9660 filesystem are read only so that is normal but it does appear that the burn process failed.

With creating a USB drive you have to use the dd command.

Code:

dd if=CentOS...iso of=/dev/sdx  where x is the letter of your usb drive.

fatmac · 10-30-2017, 12:30 PM

When writing to optical media, always use the slowest speed, this is what happens if you don't.

To create a bootable pendrive you just have to image the .iso to the drive.

jefro · 10-30-2017, 10:34 PM

Might end up telling us more about this system. Did it ever install some linux? Did it ever boot to a usb the way you tried? Is the system new and beyond the minimal hardware needed?

Arty Ziff · 10-31-2017, 12:32 AM

Quote:

Originally Posted by jefro

Might end up telling us more about this system. Did it ever install some linux? Did it ever boot to a usb the way you tried? Is the system new and beyond the minimal hardware needed?

In the end, I installed CentOS v5 from DVD's in my library, downloaded and burned bootable images of CentOS v7, and did a clean install.

Pretty sure if I knew more or had more time, I could look at logs and find where things went belly-up with the original, but in the end, this did it.

But I did learn a whole lot about mounting, unmounting, and formatting various mediums...

jefro · 10-31-2017, 10:01 PM

Thanks for the update and solution.

You will find a lot has changed between 5 and 7.