Moving installation of pclinuxos to new hard drive

[Old-Polack]

That just blew my mind.  I'm gonna need a bit of time and a brain massage for that to sink in...

After reading your whole post several times, I still don't understand how the boot configuration is determined.  I specified the MBR of /dev/sda to look at /dev/sdb2/boot/grub/menu.lst in the Arch installation (or at least that's what I am guessing happened).  How do I control that now?  What if I want to change back to using my old file (/dev/sda4/boot/grub/menu.lst)?

And what about the MBR on /dev/sdb?  Why isn't it clamoring to have a menu.lst file to point to?

How does the arbitration between the MBR of two hard drives happen? Is it always "hd0" that gets first dibs? (and if there is a boot config pointer there, all others are ignored?)

Maybe your description of your own system answered those questions and I just didn't get it.  Sorry if I'm seeming dense.  I appreciate all the help. 

Demonstration:

Grub native install, to reinstall grub to the MBR of /dev/sda the current boot drive, therefore (hd0).

[root@littleboy ~]# grub            <Enter>


    GNU GRUB  version 0.97  (640K lower / 3072K upper memory)

 [ Minimal BASH-like line editing is supported.  For the first word, TAB
   lists possible command completions.  Anywhere else TAB lists the possible
   completions of a device/filename. ]

grub>                  <-- The grub prompt... yours will not be blue.

The actual process complete, from an actual installation as I write this;

grub> find /boot/grub/stage2
 (hd0,0)                                   <-- This is my master grub with this setup, so the one I choose.
 (hd1,0)
 (hd1,6)
 (hd2,0)
 (hd2,6)
 (hd2,7)
 (hd2,8)                                   <-- These are all the places grub is currently found. Any one could be made the master.
 (hd2,12)
 (hd2,13)
 (hd3,0)
 (hd3,7)

grub> root (hd0,0)
 Filesystem type is ext2fs, partition type 0x83

grub> setup (hd0)
 Checking if "/boot/grub/stage1" exists... yes
 Checking if "/boot/grub/stage2" exists... yes
 Checking if "/boot/grub/e2fs_stage1_5" exists... yes
 Running "embed /boot/grub/e2fs_stage1_5 (hd0)"...  17 sectors are embedded.
succeeded
 Running "install /boot/grub/stage1 (hd0) (hd0)1+17 p (hd0,0)/boot/grub/stage2 /boot/grub/menu.lst"... succeeded
Done.

grub> quit

[root@littleboy ~]#

That's it. I could have chosen any of the results from the first command to be the root in the second command, and could have installed it in the MBR of the drive of my choosing, or the / partition, if I wanted to set up a chainloader +1 boot stanza.

[csolomon]

Wow, that's great info.  And you explain it very well. Thanks!

Demonstration:

Grub native install, to reinstall grub to the MBR of /dev/sda the current boot drive, therefore (hd0).

[root@littleboy ~]# grub            <Enter>


    GNU GRUB  version 0.97  (640K lower / 3072K upper memory)

 [ Minimal BASH-like line editing is supported.  For the first word, TAB
   lists possible command completions.  Anywhere else TAB lists the possible
   completions of a device/filename. ]

grub>                  <-- The grub prompt... yours will not be blue.

The actual process complete, from an actual installation as I write this;

grub> find /boot/grub/stage2
 (hd0,0)                                   <-- This is my master grub with this setup, so the one I choose.
 (hd1,0)
 (hd1,6)
 (hd2,0)
 (hd2,6)
 (hd2,7)
 (hd2,8)                                   <-- These are all the places grub is currently found. Any one could be made the master.
 (hd2,12)
 (hd2,13)
 (hd3,0)
 (hd3,7)

grub> root (hd0,0)
 Filesystem type is ext2fs, partition type 0x83

grub> setup (hd0)
 Checking if "/boot/grub/stage1" exists... yes
 Checking if "/boot/grub/stage2" exists... yes
 Checking if "/boot/grub/e2fs_stage1_5" exists... yes
 Running "embed /boot/grub/e2fs_stage1_5 (hd0)"...  17 sectors are embedded.
succeeded
 Running "install /boot/grub/stage1 (hd0) (hd0)1+17 p (hd0,0)/boot/grub/stage2 /boot/grub/menu.lst"... succeeded
Done.

grub> quit

[root@littleboy ~]#

That's it. I could have chosen any of the results from the first command to be the root in the second command, and could have installed it in the MBR of the drive of my choosing, or the / partition, if I wanted to set up a chainloader +1 boot stanza.

Of course I have more questions   When the computer is booting, does each successive hard drive get its MBR checked to see if there is a boot command?  So if I installed grub to /dev/sdb (hd1), then /dev/sda (hd0) would be checked first, find nothing, then look at hd1? 

I've seen some people recommend making a small /boot partition as the first partition of a new hard drive.  I haven't done this, so it's obviously not strictly necessary, but why is it a recommendation?  (I have SATA drives if it matters)

So why do you have so many grub files? You said in the previous post that you "install all new installation's grub to the partition's boot sector".  So for each OS, you have a /boot partition, and in each one, you have grub.  Why?  Doesn't that get confusing? Why not just have the master (on your hd0) and maybe a backup one for each hard drive (in case hd0 fails)?

[Old-Polack]

Wow, that's great info.  And you explain it very well. Thanks!

Of course I have more questions   When the computer is booting, does each successive hard drive get its MBR checked to see if there is a boot command?  So if I installed grub to /dev/sdb (hd1), then /dev/sda (hd0) would be checked first, find nothing, then look at hd1? 

Older BIOS would seek, if the first device did not have boot code in the MBR, to see if it existed in another. The order of search was fixed starting with /dev/hda. With newer BIOS one preselects which drive is the boot drive, and can change that at each boot, so I don't know if it still has the search built in.

I've seen some people recommend making a small /boot partition as the first partition of a new hard drive.  I haven't done this, so it's obviously not strictly necessary, but why is it a recommendation?  (I have SATA drives if it matters)

Back when, it was necessary because the boot loader could not see past the first 8 GB of the hard drive. When a boot partition is mentioned now, the first reaction is, "not needed anymore". I have a boot partition on each drive because it protects the kernels and such from being overwritten during upgrades. I don't normally mount the partition so the running OS doesn't know its there. If the kernel is upgraded, it happens in the /boot directory. If that kernel fails to boot, the old working kernel is safe on the boot partition waiting to be used.

So why do you have so many grub files? You said in the previous post that you "install all new installation's grub to the partition's boot sector".  So for each OS, you have a /boot partition, and in each one, you have grub.  Why?  Doesn't that get confusing? Why not just have the master (on your hd0) and maybe a backup one for each hard drive (in case hd0 fails)?

Each installation installs grub someplace. If it doesn't, there is no menu.lst created. If one doesn't want the new grub to overwrite the existing master grub what better place to install it than the boot sector of the / partition? From there it can be called by a simple chainloader stanza, or simply ignored. It hurts nothing being there, and the first stanza of the new menu.lst can be copied to the master menu.lst, and it's sure to be correct.

For each hard drive I have a single boot partition that can boot all the OS on the machine, If three drives are removed, the remaining one can still boot the OS installed on it. Each drive can be independently installed, or installed in combination with the others. This is handy, seeing as two of the drives are USB/ESATA external drives. I can plug either into a USB port of any computer that is capable of booting to a USB drive, and have my desktop available to me, along with a considerable amount of personal data on the rest of the 750-1000 GB of the drive. The boot partitions are basically backups of each other, so I'd have to loose all four before I'd be locked out of my machine. Not likely.

[csolomon]

Back when, it was necessary because the boot loader could not see past the first 8 GB of the hard drive. When a boot partition is mentioned now, the first reaction is, "not needed anymore". I have a boot partition on each drive because it protects the kernels and such from being overwritten during upgrades. I don't normally mount the partition so the running OS doesn't know its there. If the kernel is upgraded, it happens in the /boot directory. If that kernel fails to boot, the old working kernel is safe on the boot partition waiting to be used.

When you install a new OS, how big do you make your /boot partition? 

Also wanted to thank you for the detailed grub information above.  It saved me from panicking when I deleted the boot record on a drive last night.  At least that's what I gather that I did.  I was installing another distro to the second hard drive (hd1), which grub had already been setup to use as it's boot location. I didn't like the partition scheme that I'd already setup, so I deleted the partition table and remade it.  Well, when I rebooted, the computer halted on boot with Grub error 15 or something like that. 

Realizing what I must have done, I booted to a Parted Magic ISO, loaded up grub and told it to use the menu.lst file on hd0.  Simple as that.  So... thanks for preventing a freakout and meltdown!

[Old-Polack]

When you install a new OS, how big do you make your /boot partition? 

A boot partition is not necessarily a /boot partition. It becomes a /boot partition only if it is mounted on the /boot directory.

I usually only use 100 MB, but with the number of kernels I've been testing, ran out of space the other day while trying to copy the Beta 2 /boot directory. My second partition is always swap, so it was no problem to use the swapoff command to "unmount" that partition, delete it, and the boot partition, recreate the boot partition at 200 MB, then recreate the swap partition in the remaining space between sda1 and sda3. I used resize2fs to expand the existing ext3 fs in sda1 to fill out the new partition size, then finished the Beta 2 /boot directory copy.

The boot partition is normally created on a new, or freshly wiped, drive, before installing any OS. One boot partition serves all OS, so there is no need to create another when a second or third OS is installed.

[csolomon]

A boot partition is not necessarily a /boot partition. It becomes a /boot partition only if it is mounted on the /boot directory.


The boot partition is normally created on a new, or freshly wiped, drive, before installing any OS. One boot partition serves all OS, so there is no need to create another when a second or third OS is installed.

So I think I'm going to wipe my 2nd hard drive and start over.  What scheme would you recommend? I plan on installing 4 distros and having a shared /home.  So I was thinking:

/sdb1  (boot)  100MB, primary
/sdb2  (swap) 2GB, primary
/sdb3  (OS1)  35GB, primary
/sdb4  n/a      35GB, extended
/sdb5  (OS2)  35GB
/sdb6  (OS3)  35GB
/sdb7  (OS4)  35GB
/sdb8  /home  ~100GB

Does that seem reasonable? 

And if I understood you're explanation correctly, when I install each OS, I should tell grub to install the boot loader to /sdb1?  Then, if I want the /dev/sda boot loader to be the master, I can just add the stanzas from the /sdb1 menu.lst file to the /sda menu.lst file and use grub to install back on /sda (hd0).  Is that right?

[Old-Polack]

A boot partition is not necessarily a /boot partition. It becomes a /boot partition only if it is mounted on the /boot directory.


The boot partition is normally created on a new, or freshly wiped, drive, before installing any OS. One boot partition serves all OS, so there is no need to create another when a second or third OS is installed.

So I think I'm going to wipe my 2nd hard drive and start over.  What scheme would you recommend? I plan on installing 4 distros and having a shared /home.  So I was thinking:

/sdb1  (boot)  100MB, primary
/sdb2  (swap) 2GB, primary
/sdb3  (OS1)  35GB, primary
/sdb4  n/a      35GB, extended
/sdb5  (OS2)  35GB
/sdb6  (OS3)  35GB
/sdb7  (OS4)  35GB
/sdb8  /home  ~100GB

Does that seem reasonable? 

And if I understood you're explanation correctly, when I install each OS, I should tell grub to install the boot loader to /sdb1?  Then, if I want the /dev/sda boot loader to be the master, I can just add the stanzas from the /sdb1 menu.lst file to the /sda menu.lst file and use grub to install back on /sda (hd0).  Is that right?

Item #1 Don't share a single /home with different OS. Configuration files are stored there in the .<whatever> directories and files, and they may well be different between versions and distros. Your / partitions are large enough to have /home and it's configs there, and sda8 could be mounted somewhere inside your users /home/<user> directory on each OS. I have two mounted that way, the /etc/fstab lines are;

LABEL=TR5-Documents     /home/polack/Documents    ext3    defaults                1 2
LABEL=Documents2          /home/polack/Documents2  ext3    defaults                1 2

These lines are the same for each OS's /etc/fstab.

Item #2 Each OS grub is installed to that OS's own / partition, except for the first, which is installed to the MBR. That one is the master grub that controls the booting of all the installations.

Item #3 You copy the first stanza of each new menu.lst to the master menu.lst and save the file. Pick a descriptive title for each installation, not the default linux. On next boot the new OS will be in the boot menu. There is no reason to reinstall grub to the MBR; it reads the master menu.lst and reports what it finds as the boot menu. I added and removed dozens of stanzas to the same menu.lst, for four years, without reinstalling grub. 

Item #4 The partition layout seems fine, except as noted above, pertaining to /home.

[nerdful1]

wow o-p get that in the magazine now!

[wyzwyk]

o-p, your replies to this post are very instructive and most helpful.  Thank you! 

[csolomon]

Item #1 Don't share a single /home with different OS. Configuration files are stored there in the .<whatever> directories and files, and they may well be different between versions and distros. Your / partitions are large enough to have /home and it's configs there, and sda8 could be mounted somewhere inside your users /home/<user> directory on each OS. I have two mounted that way, the /etc/fstab lines are;

LABEL=TR5-Documents     /home/polack/Documents    ext3    defaults                1 2
LABEL=Documents2          /home/polack/Documents2  ext3    defaults                1 2

These lines are the same for each OS's /etc/fstab.

Item #2 Each OS grub is installed to that OS's own / partition, except for the first, which is installed to the MBR. That one is the master grub that controls the booting of all the installations.

Item #3 You copy the first stanza of each new menu.lst to the master menu.lst and save the file. Pick a descriptive title for each installation, not the default linux. On next boot the new OS will be in the boot menu. There is no reason to reinstall grub to the MBR; it reads the master menu.lst and reports what it finds as the boot menu. I added and removed dozens of stanzas to the same menu.lst, for four years, without reinstalling grub.  

Item #4 The partition layout seems fine, except as noted above, pertaining to /home.

Good info.  That's a great point about /home... I hadn't considered that.  That's a cool way you have the /home/polack/Documents setup.

So when installing a new OS, how do you specify that the kernel is installed in the boot partition?  I'm not sure I understood what you are using that 1st, boot partition for.  Do you mean that after installation, you manually copy the kernel files there, or do you do it as part of the automated installation process?

edit:  what I mean is... during the installation program, do I specify the "boot partition" (/dev/sdb1) as a mount point for /boot?  It seems like "no", because you previously said that you don't normally mount this partition.  And also it seems like that wouldn't work with multiple OSes since the vmlinuz symlinks would overwrite each other...

[Old-Polack]

Item #1 Don't share a single /home with different OS. Configuration files are stored there in the .<whatever> directories and files, and they may well be different between versions and distros. Your / partitions are large enough to have /home and it's configs there, and sda8 could be mounted somewhere inside your users /home/<user> directory on each OS. I have two mounted that way, the /etc/fstab lines are;

LABEL=TR5-Documents     /home/polack/Documents    ext3    defaults                1 2
LABEL=Documents2          /home/polack/Documents2  ext3    defaults                1 2

These lines are the same for each OS's /etc/fstab.

Item #2 Each OS grub is installed to that OS's own / partition, except for the first, which is installed to the MBR. That one is the master grub that controls the booting of all the installations.

Item #3 You copy the first stanza of each new menu.lst to the master menu.lst and save the file. Pick a descriptive title for each installation, not the default linux. On next boot the new OS will be in the boot menu. There is no reason to reinstall grub to the MBR; it reads the master menu.lst and reports what it finds as the boot menu. I added and removed dozens of stanzas to the same menu.lst, for four years, without reinstalling grub. 

Item #4 The partition layout seems fine, except as noted above, pertaining to /home.

Good info.  That's a great point about /home... I hadn't considered that.  That's a cool way you have the /home/polack/Documents setup.

So when installing a new OS, how do you specify that the kernel is installed in the boot partition?  I'm not sure I understood what you are using that 1st, boot partition for.  Do you mean that after installation, you manually copy the kernel files there, or do you do it as part of the automated installation process?

For the installation of the first OS I specify that the boot partition be mounted on /boot. All the proper files then end up on the partition. Later, I unmount the partition from /boot, then mount it on /mnt/boot. From there I copy all the content of /mnt/boot to /boot, which at that point is an empty directory. In /etc/fstab I comment out the line specifying the partition being mounted at /boot. I add a stanza to the master menu.lst on the boot partition to allow booting to the kernel now in the /boot directory on the / partition. This is insurance that if either kernel or initrd image is damaged, I can still boot to the other set.

From that point on, the boot partition is never mounted on /boot in any installed OS. If the OS that originally installed grub to the partition is removed, grub still remains on the boot partition as the master grub.

When other OS are installed, If any damage comes to the boot partition files, any other grub can be made the temporary master to get a system booted, then the files from the appropriate /boot directory can be copied back to the boot partition, like any restore from any other backup. When the files are again intact, the boot partition grub can again be made the master.

[csolomon]

For the installation of the first OS I specify that the boot partition be mounted on /boot. All the proper files then end up on the partition.

Ok, done.

Later, I unmount the partition from /boot, then mount it on /mnt/boot. From there I copy all the content of /mnt/boot to /boot, which at that point is an empty directory.

Can I just do:

Code: [Select]

cp -r /mnt/sdb1/* /mnt/sdb3/boot?  Any special way to execute the command so that everything is copied perfectly?  or is the command I posted sufficient?

In /etc/fstab I comment out the line specifying the partition being mounted at /boot. I add a stanza to the master menu.lst on the boot partition to allow booting to the kernel now in the /boot directory on the / partition.

So I have to change the path and the "root":
change

Code: [Select]

kernel (hd1,0)/vmlinuzto

Code: [Select]

kernel (hd1,2)/boot/vmlinuz
Is that right?

This is insurance that if either kernel or initrd image is damaged, I can still boot to the other set.

From that point on, the boot partition is never mounted on /boot in any installed OS. If the OS that originally installed grub to the partition is removed, grub still remains on the boot partition as the master grub.

I think I actually get it now.  You are protecting the "original" boot files by copying them, then unmounting the originals.  You can always the remount them if something happens to the new /boot files.

[Old-Polack]

For the installation of the first OS I specify that the boot partition be mounted on /boot. All the proper files then end up on the partition.

Ok, done.

Later, I unmount the partition from /boot, then mount it on /mnt/boot. From there I copy all the content of /mnt/boot to /boot, which at that point is an empty directory.

Can I just do:

Code: [Select]

cp -r /mnt/sdb1/* /mnt/sdb3/boot?  Any special way to execute the command so that everything is copied perfectly?  or is the command I posted sufficient?

I'm assuming that this is being done from the liveCD. Is that correct? I'd use cp -a /mnt/sdb1/* /mnt/sdb3/boot

In /etc/fstab I comment out the line specifying the partition being mounted at /boot. I add a stanza to the master menu.lst on the boot partition to allow booting to the kernel now in the /boot directory on the / partition.

So I have to change the path and the "root":
change

Code: [Select]

kernel (hd1,0)/vmlinuzto

Code: [Select]

kernel (hd1,2)/boot/vmlinuz
Is that right?

Were it my drive, I would have made sdb the boot drive in BIOS, before doing the installation, so all the boot partition root references would be (hd0,0) and I would have installed grub to (hd0), which under those circumstances would put grub in the MBR of the drive on which all the Linux OS will reside, sdb. If by chance you did install grub to the MBR of sdb, it will have to be made the boot drive to use that grub, and at that time any reference to (hd1,0) will have it looking for the kernel and initrd image on sda.

If you installed grub to the MBR of sda, you now have a situation where the new installation will boot with the menu.lst stanzas as is, but if either drive fails, you will be unable to boot any OS on either drive. Any failure = total failure. Kind of makes all the redundancy moot, don'tcha  think?

This is insurance that if either kernel or initrd image is damaged, I can still boot to the other set.

From that point on, the boot partition is never mounted on /boot in any installed OS. If the OS that originally installed grub to the partition is removed, grub still remains on the boot partition as the master grub.

I think I actually get it now.  You are protecting the "original" boot files by copying them, then unmounting the originals.  You can always remount them if something happens to the new /boot files.

Actually you can boot from either kernel/initrd set of files interchangeably, and either is the backup of the other. Failsafe through redundancy.

[csolomon]

I'm assuming that this is being done from the liveCD. Is that correct? I'd use cp -a /mnt/sdb1/* /mnt/sdb3/boot

Well, I was gonna do it from my first linux installation (on /dev/sda3), but there's no reason I can't do it from a live CD.

Were it my drive, I would have made sdb the boot drive in BIOS, before doing the installation, so all the boot partition root references would be (hd0,0) and I would have installed grub to (hd0), which under those circumstances would put grub in the MBR of the drive on which all the Linux OS will reside, sdb. If by chance you did install grub to the MBR of sdb, it will have to be made the boot drive to use that grub, and at that time any reference to (hd1,0) will have it looking for the kernel and initrd image on sda.

If you installed grub to the MBR of sda, you now have a situation where the new installation will boot with the menu.lst stanzas as is, but if either drive fails, you will be unable to boot any OS on either drive. Any failure = total failure. Kind of makes all the redundancy moot, don'tcha  think?

Well, I was keeping /dev/sda3 the boot (setup/root hd in grub) drive because that's where I first installed linux and it's my newest drive.  I know it doesn't always work like that, but my 2nd drive is a few years old and I figured it is more likely to "fail".  

Either way, whether I was gonna have it setup how you recommended before.... having each physical hard drive have its own menu.list file capable of booting the whole drive.  I'm not sure how either drive failing would prevent me from booting the computer, as both drives have menu.lst files that can boot the entire drive (and in the case of the /dev/sda3 menu.lst, it can boot all the drives).  Maybe I'm missing something though...