I have ubuntu 9.10 on /dev/sda6 (root) and /dev/sda7 (home) on a
gateway computer with sata hard drive. My target configuration is
Slack 13.0 on /dev/sda1 (root) and /dev/sda2 (home). My last
slackware installation was 10.00 in 2004. At that time lilo was
(to the best of my memory) the only option.

1)Do I know have a choice of grub or lilo?

2)Are there any preparations that I might need to do to preserve
boot access to my current ubuntu installation?

3)I am very curious about http://www.slackware.org/install/bootdisk.php
and http://www.slackware.org/install/rootdisk.php. I don't even have
a floppy disk drive on my computer. That looks like the instructions for
my first install of slack back in 1995 or 1996.

Comments, caveats and (especially) links to documentation clarifying
question 1, 2 and 3 are invited.

thanks
tim

There are several choices here - you could install lilo to the MBR and have lilo boot Ubuntu and Slackware (you may need to manually edit lilo.conf for this) and install lilo to the MBR, you could install lilo to the root of the slackware partition and chainload it from grub (probably easiest at first) or add an entry for slackware to grub's menu.1st (this may not work with ext4 Slackware partitions).
Thats old stuff about building a boot floppy - I wouldn't worry about that now.

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Here is a quick explanation of partitions and booting.

A standard PC hard disk partition table supports four main partitions. There are two types of main partitions, Primary and Extended. You can only create one Extended partition, and all the rest of the partitions must be Primary. You can also create four Primary partitions with no Extended partition.

An Extended partition is essentially a container for any number of Logial partitions. Logical partitions are not "seen" in the partition table, but are recorded inside the Extended partition. Most partitioning programs find and display the Logical partitions along with the Primary and Extended partitions.

In Linux, Primary partitions have partition numbers from 1 through 4. An Extended partition has one of the numbers from 1 through 4 but that number usually doesn't show up as a separate device name. Logical partitions inside an Extended partition have numbers 5 and above.

When you first start the computer the BIOS always loads the first sector of the hard disk (the Master Boot Record) and executes the software there if the signature bytes at the end of the sector are correct. The first hard disk sector (MBR) has both the master boot code and the partition table. The default MBR software searches the partition table for the first Active (Boot) partition, then loads and executes the first sector (boot sector) of that partition. Installing a boot loader to the MBR replaces the default code and starts the boot loader immediately. The BIOS does not know or care about partitions, it is only the software in the MBR, or the boot loader that knows or cares anything about partitions.

Each Primary partition can have a partition boot sector containing boot software to start a boot loader. If additional sectors have to be loaded, the software in the partition boot sector has to load those other sectors. The default MBR software just loads the first sector of the partition. If you install a boot loader to a partition boot sector, then it writes the appropriate software in the boot sector. A partition boot sector is never loaded directly. Either the MBR software, or some boot loader chains to it.

Thus there are five places (boot sectors) where you can "install" a boot loader (the MBR and four Primary partition boot sectors). Only the MBR is guaranteed to be loaded and executed since the BIOS always does that. If you leave the default code in the MBR (I recommend that) then you can change the default partition boot sector (and boot loader) by changing the Active (Boot) flags for the partitions. When you install a boot loader to the MBR then that boot loader ALWAYS starts first and you must install different MBR software to change the default.

Logical partitions (in an Extended partition) do not have boot sectors, and should not contain the software (files) for a boot loader. You cannot "install" a boot loader to a Logical or Extended partition. A Logical partition CAN contain an operating system loaded by a boot loader. Only the boot loader has to be in some Primary partition. The Linux kernel and initrd can be placed in a Logical partition, and so can the root file system "/". Windows (the WINDOWS folder, etc.) can can also be located in a Logical partition, but the Windows boot loader (NTLDR, bootmgr) cannot.

With a complicated multi-boot configuration it may be desirable to put ONLY the boot loaders in Primary partitions and put all the rest of the operating system files in Logical partitions. The Primary partitions containing a boot loader can be quite small.

The BIOS does not know about partitions, only hard disk sectors relative to the beginning of the hard disk. The BIOS does know about hard disks. I really mean hard disks and not drive letters, partitions or Linux device names. Each hard disk has an 8-bit ID. Boot sector software usually has a hard disk ID for the first hard disk.

Here are the hard disk IDs (and floppy disk IDs) used by the BIOS.

80 (hex) - First hard disk (hda, sda, hd0)
81 (hex) - Second hard disk (hdb, sdb, hd1)
82 (hex) - Third hard disk (hdc, sdc, hd2)
83 (hex) - Fourth hard disk (hdd, sdd, hd3)
00 (hex) - First Floppy Drive (floppy, fd0)
01 (hex) - Second Floppy drive (fd1)

Although an operating system treats a CD/DVD drive similarly to a hard disk, the BIOS does not. There are no BIOS functions to access a CD-ROM drive. The BIOS can load and start a boot image from a CD/DVD. The BIOS supports booting from CD/DVD in two different ways, "emulation" and "no-emulation".

With emulation, the boot image on the CD/DVD appears to be a normal floppy or hard disk, and is accessed using the normal BIOS functions for those. Any real floppy or hard disk drive is assigned the next available ID. Older operating system boot CDs such as Windows 98 use emulated floppy mode. Newer operating systems and newer BIOS software supports no-emulation booting that just loads boot software into memory and does not make the CD appear to be some other device. The no-emulation software has to have any required drivers to access the disk controller and CD/DVD drive. Windows NT (and later) use no-emulation mode. A small Linux system that fits on one floppy and loads a RAM disk can be written as a floppy-emulated CD boot image. Larger Linux systems require some kind of no-emulation loader. For example, one can install GRUB to the boot image of a CD and GRUB can access the CD-ROM to load the kernel and initrd.

What is "chaining"? Since each of the five boot sectors must have enough software to completely load some boot loader, any boot loader can start a different boot loader, by "jumping" to the software in the boot sector for the other boot loader. When chaining, a boot loader, reads the boot sector, and then starts executing the software in the sector (the new software never returns). This allows a boot loader to start any other boot loader without knowing anything about the other boot loader or the file systems the other boot loader supports. Only the location of one 512-byte sector has to be known.

GRUB and LILO can directly read and chain to any sector (or file). Windows boot loaders (NTLDR and bootmgr) can only chain to software contained in files. You can copy a boot sector from the hard disk into a file and then chain to the file. The file has to be placed in a file system that the boot loader chaining to the file understands (EX: NTFS/FAT16/FAT32 and NOT ext3 for Windows).

An advantage of using files is that you can "patch" the software in the files. You can also have any number of files, while you are limited to only the five actual boot sectors for directly starting a boot loader. One reason to "patch" boot code is to support boot loaders on the second hard disk. As long as the files contain the correct software (or copy of a valid boot sector) you can start boot loaders even that are not installed to any of the five boot sectors. That allows you to support more than five boot loaders.

You can use GRUB with Slackware but you have to install it yourself. It isn't automatically installed and configured by Slackware setup. Either install LILO first and then change it later, or use the "chroot" command after installing Slackware (before rebooting) and install GRUB. Make sure that you use the latest, patched GRUB included on the Slackware CD (or web site) to support 256-byte inodes.

The partitions "/dev/sda6" and "/dev/sda7" are both logical partitions inside an extended partition. You should not normally place the boot loader in a logical partition. You probably have a boot loader already located in some primary partition (sda1 through sda4).

This can be a bit confusing because there are two parts to the boot loader. The first part is the boot sector where you "install" the boot loader. The boot sector can be the MBR or one of the four primary partition boot sectors. The second part is the set of files making up the boot loader program. Those files are usually located in one of the four primary partitions. I always prefer to "install" a boot loader to the same partition boot sector where the rest of the boot loader program files are located. If you don't install anything else to the MBR, it usually chains to the Active partition's boot sector. Thus you can do exactly the same thing by marking the correct partition Active (Boot) as you can by installing a boot loader to the MBR.

To install Slackware to "sda1" you have to create and format the first primary partition using ext3 (or some other Linux compatible filesystem). You can put "/home" in "sda2" if you create and format the second primary partition to contain the filesystem for "/home". If there is no free space at the beginning of the hard disk then you have to shrink and move, or delete existing partitions.

May I suggest that it is better to place "/home" in a logical partition (in the extended partition) since it cannot contain boot loader files or a boot sector. That will allow creation of an additional primary partition for some other OS later.

The files that you should put in a primary partition are the boot loader program and the boot menu file. You can put the Linux kernel and files there too, but you can also put them in a logical partition instead. Logical partitions are "sda5", "sda6", etc.

To preserve your existing Ubuntu installation, back up the "menu.lst" and other GRUB files (probably located in "sda1"). Make sure that you do not delete "sda6" or "sda7", or use "cp -a" or "tar" to back the files up to somewhere else.

To make Ubuntu boot again, add it to the GRUB menu for Slackware in "sda1". If you want to keep a separate copy of GRUB for Ubuntu, then create a "sda3" partition and put the GRUB for Ubuntu there. Then add a menu entry to Slackware GRUB to chain to Ubuntu GRUB. If you put Slackware "/home" in a logical partition then you can install Ubuntu grub to "sda2" instead.

To successfully install multiple operating systems it is important to understand how the system is partitioned and configured first. What are the partitions? What software is installed to the MBR? What software is installed to each possible Primary partition? Where are the files for each operating system?

Next plan how you will configure the partitions, where you will place the software (files) for each boot loader, and where (to what sector) you will "install" each boot loader. Will you use the default MBR software (and Active/Boot flags) or start a boot loader directly?

Have the required boot discs in order to install or repair the boot loaders, format or resize partitions, etc. Back up important files even if you don't expect to lose them. Things can go wrong.

Re-size and move/copy the partitions to configure the hard disk as planned. After you have the partitioning correct, install the first boot loader or standard MBR software to the MBR. Next install the boot loader for each Primary partition boot sector. Configure the menus during or after installation of boot loaders. LILO is configured before installation of LILO. GRUB "menu.lst" can be configured before or after installing GRUB.

What makes boot configuration complicated is the number of choices. There are a lot of ways you can configure the five boot sectors and boot loader menus.

4 members found this post helpful.

I'm a big noob to slackware (now my distro of choice cuz it's fooking brilliant), but when i installed 13 on a second partition (got ubuntu 8.04 on the first partition), all i did was chose not to install lilo during installation, and then just add an entry to my menu.lst when in unbuntu.

It works for me, but since doing this i seen a lot a people saying this isnt the best way to go about it.

I really appreciate the extensive information given here. Thanks very much!

This is a bit off topic, but there isn't anything wrong with what you did. Just keep in mind that you have to install some boot loader for Slackware if you later remove the Ubuntu partition. The default Ubuntu installation will install Ubuntu's GRUB to the Master Boot Record and always start that first. If you remove Ubuntu then Slackware will have no boot loader. That's easily fixed using a Slackware boot CD.

What I usually do (even with Ubuntu) is install the boot loader for the distro in the same partition with the distro, and then set the Active ("Boot") flag for the boot loader that I want started first.

To "fix" what you did, you would have to restore the default boot code to the MBR (or uninstall Ubuntu GRUB to restore it). Then reinstall Ubuntu's GRUB to the Ubuntu partition and install Slackware's boot loader (LILO or GRUB) to the Slackware partition. Add menu entries to Ubuntu or Slackware to chain to the other distro's partition boot sector. Set the Active ("Boot") flag for either Ubuntu or Slackware depending on which boot loader you want to start first. If you later uninstall either Slackware or Ubuntu then you may have set the Active ("Boot") flag for the remaining distro using "fdisk" or "cfdisk".

I don't see any reason to "fix" what you have unless you later make changes and it won't boot. The most important thing when making any changes is to have a recent back up of your important files and the necessary boot discs to install or repair boot loaders.

If you're going to run multiple distros you may just want to eventually create a small Primary partition for GRUB and keep everything else in other partitions. If you make the partition FAT16 or FAT32 you can even put the Windows boot loaders (NTLDR and bootmgr) there along with GRUB. You will have to create boot sector files to start the Windows boot loaders though. A single partition has only one boot sector and only starts one boot loader using that boot sector.

Erik,
Thanks for this. I always knew i was going to enter a world of hurt when i decided to get rid of ubuntu (which is soon), so all of your advice on this thread has been very very useful for me. Thanks again mate,
mute

Wow! I am looking at all the post and thinking that I am in your boat. In fact, I am facing these same questions in my other post. Grub is way easier to use than LILO and Grub has documentation. There is a reason why it's the bootloader of choice for most distros, and LILO is not. If I understand correctly, one has to edit & then reinstall LILO every time a kernel is updated or replaced! I edited my grub menu.lst so that it would chainload LILO. Then LILO screws up the boot flags, so I am going to dump LILO and install Grub. However, good luck. Please post your successes and failures, so that others, myself included, can learn.

With either GRUB or LILO, one must add the new kernel to some configuration file.. And then, yes, with LILO, the loader needs to be "re-installed", but it isn't like installing an application or a package-- it's simply typing the word "lilo" at the command prompt. Pretty easy

Sasha

Yes but before you type in 'lilo' you need to mount the disks which contains the other distros' kernels (if you're multi-booting several distros) and it gets boring if you frequently update kernels. for example. I don't use Ubuntu but I have Pardus which is somewhat similar, and it updates its kernel package pretty often (and it uses Grub). I still use LILO on the MBR and I install grub to the boot sector of the Pardus partition (and chainload it from LILO). This way I don't need to re-run lilo every time Pardus updates its kernel. Doing it the other way around (grub on MBR, chainloading LILO) would practically be the same, of course. I'm more accustomed to work with LILO so that's my choice for MBR.

I agree with you that GRUB has some advantages over LILO. I prefer to have my Windows Vista boot loader (bootmgr) start first and chain to my Linux boot loader. In order to do that I have to copy the boot sector for GRUB or LILO into a file and then move the file to the NTFS partition.

If I use LILO I have to repeatedly update that file with a copy of the boot sector after every LILO configuration change (even minor menu changes). Using GRUB I only have to do that copy once, and not after each menu configuration or kernel change.

I use a "fake hardware RAID" controller on two of my computers. I can't easily install LILO on those machines because it is never able to correctly determine the BIOS drive IDs. With GRUB I can boot from a GRUB floppy and install GRUB entirely using the "native" BIOS support in GRUB. Then it has no problem accessing the disks and writing the correct boot sectors for BIOS drive IDs.

GRUB allows most of the commands to be entered from a "native" command prompt. I can boot files that don't even appear in the menu or edit the existing entries in an emergency. LILO does support some settings changes during boot but is not nearly as flexible.

So far the only thing that LILO seems to do better than GRUB is a boot splash screen. GRUB can support boot splash screens but I've never been able to get that to work.

Ironically I use Slackware, and that is one of the few distros that uses LILO in the standard setup. I have to install and configure GRUB after (or during) installation of Slackware.

GRUB 2 seems daunting and it may be that LILO's simplicity will become more popular than the complexity of GRUB 2. Until then GRUB 0.9x is my preference for a boot loader.

I will admit that it took me a while to understand GRUB but the documentation was quite complete. LILO hides a lot of the messy details of BIOS drive IDs and sector addressing but that can be bad as well as good in some situations.

Boot loaders may well be another passionate subject similar to linux distros. My philosophy is to stick to discussing the abilities and limitations of something rather than getting into a judgment about what is "better". Everyone is different and what may be "best" for me is not necessarily best for someone else.

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Grub2, from what I've read, only requires that one put the same additional entries in a different location. (Location 50 or something like that) same old business; new location. Then there is venerable, easy-to-use legacy Grub which I do not think will ever go away, so I cannot fathom LILO becoming more popular than grub.
I actually started with LILO cause I did not know the difference between the two. Then I attempted to make a boot floppy with LILO and was frustrated to no end. Then I tried Grub. Making an emergency rescue boot floppy was so easy once I found (GOOD!) documentation. Creating the emergency rescue boot usb was easy too, basically, a copy & paste.


I Like your philosophy, but I can only partially embrace it. While I agree that LILO could be the bootloader of choice due to reasons of personal preference or some rare & unique circumstance, one cannot lose sight of the fact that there are reasons for grub to be the default bootloader of choice for most distributions of Linux. Therefore, it's easy to use facts to show that Grub is more flexible than LILO, and greater flexibility and ease of use is superiority in my mind and the minds of those who release the various distributions of Linux.
Consequently, if someone is offended by criticism of LILO, I would postulate the following: The offended party has probably spent many painful hours learning LILO. The offended party's individual learning experiences with LILO probably engendered feelings of accomplishment, pride, and increased self-worth. Thus, any criticism of LILO probably diminishes their sense of accomplishment, pride and self-worth. Why else would someone be passionate over a bootloader or a Gnome vs KDE?

I prefer GRUB but I have ran into a problem with getting it to work with a Gateway AMD Phenom X4. It fails in its transition from stage1 to stage1.5 After trying several things and reinstalls, I have come to the conclusion I am going have to use LILO. It has been years since I used LILO. I was wondering if anyone knows of a Ubuntu disk with LILO as the main boot-loader? I would appreciate it since it save me some trouble of manually installing it.

If anyone has any experience in overcoming the problem I mention concerning GRUB I would appreciate that, since I am concerned that since this is not my computer but belongs to another person. My concern is that after an upgrade, LILO may be knocked out and leave him stranded if I am away on a extended trip.

I do not understand why Grub would fail with your computer setup. A perfunctory check of Google, your system and Grub returned nothing unusual, but perhaps I did not look deep enough. Is root on it's own partition with grub installed in it? I know that window's malicious software removal tool will remove grub from the MBR. Did you reinstall your system from a backup? Did partitions change? These are the only times that grub has given me problems similar to what you described. For me, grub will even boot 10 mb systems installed on a flashdrive, so I have to wonder what you're doing.

If my memory serves me correctly, every Ubuntu CD or DVD offers LILO as an alternative bootloader. Certainly all of the alternative installation CDs will give you LILO as a second boot option.

I think it would be better to get Grub running. At least with grub, one can download supergrub disk to almost automatically reinstall Grub. Additionally, it's easy to make a Grub emergency boot floppy, or a Grub emergency boot USB to boot your friend's system. The mbr can be backed up too if grub is installed there.
>
I hope I've help

I finnally got GRUB working on this computer. I went bought a new SATA HD and install it and it worked. I was trying to be cheap by slipping a PATA drive into the mix. This must have confused the system, having both SATA and PATA drives. Accessing the PATA was not a problem, just booting it up.

Sorry about that. I just hope my experience/lesson will be a help to others here.