[SOLVED] Bootdisk

tb75252 · 08-26-2016, 03:10 PM

During the installation of Slackware 14.2 I was asked whether I wanted to create a USB bootdisk.

My PC is fairly old and its BIOS does not support booting up with a USB thumb drive, so I answered "Skip". (My BIOS supports booting up with a DVD.)

Now I am wondering whether there is a way to create a DVD bootdisk. What do the experts say?

astrogeek · 08-26-2016, 03:14 PM

The DVD installation media IS the maintenance boot disk!

Just boot to your install DVD, mount the / partition of your hard drive and take it from there!

tb75252 · 08-26-2016, 03:29 PM

Quote:

Originally Posted by astrogeek

The DVD installation media IS the maintenance boot disk!

Just boot to your install DVD, mount the / partition of your hard drive and take it from there!

I see... I was hoping that a DVD bootdisk would be different than the DVD used for installation.
Why, you ask?
As a test, I booted up with the DVD install media and issued the following commands:

Code:

boot: huge.s root=/dev/sda1 rdinit= ro

Everything went fine until it reached the KDE login screen and discovered that my keyboard (USB wired) and mouse (USB wireless) were disabled and I could not do anything other than turn the PC off.

astrogeek · 08-26-2016, 04:02 PM

Well, like that you are simply booting to your installed filesystem, read-only, for better or worse, as you found out.

For an emergency or recovery boot you want to boot to the DVD media, including the root filesystem on that media.

Then mount your installed root filesystem so that you can navigate, inspect and update it as required.

If you need to chroot into the mounted filesystem after boot, to run lilo for example, just do this (replace chroot dir with actual mount point)...

Code:

mount --bind /proc <chroot dir>/proc
mount --bind /dev <chroot dir>/dev

chroot <chroot dir>

At least, that is how I use it. Maybe someone else has other habits.

tb75252 · 08-26-2016, 07:19 PM

Quote:

Originally Posted by astrogeek

Well, like that you are simply booting to your installed filesystem, read-only, for better or worse, as you found out.

For an emergency or recovery boot you want to boot to the DVD media, including the root filesystem on that media.

Then mount your installed root filesystem so that you can navigate, inspect and update it as required.

If you need to chroot into the mounted filesystem after boot, to run lilo for example, just do this (replace chroot dir with actual mount point)...

Code:

mount --bind /proc <chroot dir>/proc
mount --bind /dev <chroot dir>/dev

chroot <chroot dir>

At least, that is how I use it. Maybe someone else has other habits.

I must be doing something wrong... Say that my installation root directory is in /dev/sda1.
I issue these commands:

Code:

root@slackware:/# mount --bind /proc /dev/sda1/proc

I get the following:

Quote:

mount: mount point /dev/sda1/proc is not a directory

suppy · 08-26-2016, 07:46 PM

/dev/sda1 is a device node, not the <chroot dir> that you ought to have mounted it in

astrogeek · 08-26-2016, 08:13 PM

Quote:

Originally Posted by tb75252

I must be doing something wrong... Say that my installation root directory is in /dev/sda1.
I issue these commands:

Code:

root@slackware:/# mount --bind /proc /dev/sda1/proc

I get the following:

Sorry if I confused you, I should have explicitly included the mount instead of simply saying "mount the installed filesystem".

So, lets assume that you have booted to the DVD and logged in as root, just as you did when you installed.

From that point lets mount your installed root system root filesystem on a directory named /myslack, which we will also create...

Code:

mkdir /myslack
mount /dev/sda1 /myslack

At this point you can navigate and edit your installed system through the /myslack path,
but you are still running the booted DVD. To actually run as your installed system...

mount --bind /proc /myslack/proc
mount --bind /dev /myslack/dev

This makes the device and process nodes of the booted system available to your installed system, then...

chroot /myslack

At this point you are running (almost) just as if you had booted into run-level 3 of your installed system, and you are logged in as root. (So be careful! You may want to similarly mount --bind /sys..., but not req'd for common tasks).

From there you can edit and reinstall lilo, for example, or fix anything that is broken on the installed system.

When done just type exit to "un-chroot" back to the booted DVD and shutdown, and reboot.

tb75252 · 08-28-2016, 09:34 PM

Quote:

Originally Posted by astrogeek

Sorry if I confused you, I should have explicitly included the mount instead of simply saying "mount the installed filesystem".

So, lets assume that you have booted to the DVD and logged in as root, just as you did when you installed.

From that point lets mount your installed root system root filesystem on a directory named /myslack, which we will also create...

Code:

mkdir /myslack
mount /dev/sda1 /myslack

At this point you can navigate and edit your installed system through the /myslack path,
but you are still running the booted DVD. To actually run as your installed system...

mount --bind /proc /myslack/proc
mount --bind /dev /myslack/dev

This makes the device and process nodes of the booted system available to your installed system, then...

chroot /myslack

At this point you are running (almost) just as if you had booted into run-level 3 of your installed system, and you are logged in as root. (So be careful! You may want to similarly mount --bind /sys..., but not req'd for common tasks).

From there you can edit and reinstall lilo, for example, or fix anything that is broken on the installed system.

When done just type exit to "un-chroot" back to the booted DVD and shutdown, and reboot.

Thanks for your help!

astrogeek · 08-28-2016, 10:32 PM

You are very welcome!