:: Shell-Shocked :: Tutorial: Multiple Linux Distros

Multiple Linux distros on one drive

(With or without Windows)

Disclaimer:
This is a relatively simple setup. I don't have any servers on my system (except SAMBA, but that doesn't count), so no Apache, MySQL, or Fetchmail. Nor do I do development. I don't use KMail, Konqueror or Evolution (I'm a Mozilla Mail kinda girl). I also don't use KDE. So issues like cross-distro server logging, development project consolidation, specific KDE tools, or mail consolidation for anything other than Mozilla/Thunderbird/Netscape (if anyone is still using that) is not going to be covered here. I also still have a Windows install, so I did use Windows tools for some parts of this setup and will include that for those reading this that will also retain Windows. If your system is significantly different (you have a mail server, you have removed Windows completely, you use Evolution), you can probably adapt this tutorial to figure out the necessary changes, where I don't indicate them myself. This is a fairly rough guide, and while it worked (and still works) for me, I cannot guarantee it will work for you (because you are not me). So be very careful, and please do your research before just blindly following this guide.
Thanks.

My original goal was to have 5 installed Linux distributions multi-booting with 2 versions of Windows, with certain files available under both Windows and all distributions of Linux, and certain other files available under all distributions of Linux. My intention was to prevent duplication of large blocks of data that I would be using under all distros/OSes--- for example, N(ever)W(inter)N(ights) is some 2GB, and I had no desire to have it installed 5 times, onto 5 different partitions, just to play it under every distribution. My HDD is just not big enough for that, plus it's annoying ;-).

The files I needed under both Windows and all distributions of Linux were:

audio/video files;
installed Win applications that I would want to also run under Wine (including games);
downloaded mail;
miscellaneous personal data such as my CV, source material for my web-page-in-progress, files that I was planning to burn to CD, etc.
shared network data (data shared from me to the network, which is a Win2000 machine).

The files I needed under all distributions of Linux were:

Linux "non-installables". Most programs under Linux are installed to specific locations per distro, either via binary installers (.rpms, .debs) or scripts (Makefiles/make install, compiling from source, Slackware .tgzs, Gentoo portage scripts), but quite a few are not. Firebird/Thunderbird currently are extracted to any location you choose, as are Seti@Home, NWN, and Quake. Kingpin uses an install script, but you can choose the location. And games that you plan to install under Wine can be installed to any real location you want, by reconfiguring wine.conf. Some of these apps are really big, and since I planned to use them under all distributions I wanted them to reside in the same location. Yes, I would still have to "install" some of them more than once in order to have each disto recognize that the app was there, but if I installed them over themselves in a shared location, they would not take up extra space for the same files.

Collection point for various downloaded Linux files (drivers, miscellaneous apps that have to be compiled, loose RPMs and TGZs, icons and themes, etc.). All of these files needed to be owned by me (as a user) under all circumstances, no matter which distro I was booted into, which meant that they had to somehow be in my ~/ directory (that's my ${HOME} directory, or /home/username), as 1) that's more convenient in terms of file navigation; 2) files can only be shared to the network from one's /home directory; 3) putting them elsewhere would probably screw up the permissions, making me unable to use the files.�

Disclaimer 2:
I have explained my goals fairly thoroughly because this is not the Windows world, where you're given a plate and told to eat what's on it, period. Linux users are expected to think about what they're doing before they do it. So now, reader, you should be thinking about how your goals in installing multiple distros are different from mine, so that you can filter the following instructions based on your needs. If you haven't thought about what your needs are, you should do that now, and at least you have a place to start considering what those needs might be. Maybe you don't have a network that you need to share files back to (or need to receive files from). Maybe you don't play any games but pysol, and won't be installing games/apps under Wine/WineX. Maybe you have an FTP server or Web server that you'll want to run under all distros. How are you not me?

Oh, I suppose I should mention: I did succeed at my goal.

So, how did I do it? OK, here we go. The easiest way I found to set this up is to pre-partition before installing anything. If you have a Windows install, I suggest Partition Magic if you have it, but there are other partitioning utilities available if you don't. If you have Mandrake, running the install through the partitioning section, then rebooting is also good (DiskDrake is stupendous), or you can use any other distro's partition tool (fdisk or cfdisk) to set up the partitions. Set up all / partitions for Linux (except the swap of course) as ext2, any shared data partitions for Linux as ext3, and any partitions with shared files needed to be visible to a Windows install (either your own or one elsewhere on the network) as FAT32.

How big should your partitions be?

This of course depends on 1) how much HDD space you have; 2) how much HDD space you need (if you're not installing KDE and GNOME, you don't need as much space as if you are); 3) how much memory you have (relates to the size of the swap file); 4) what distros you're installing (some distros contain more bloat by default than others); and 5) how much space you need for the various types of shared files. Since I don't know the answer to most of these questions for you, I will only say that the minimum "comfortable" size for my Mandrake 9.1 install (Mandrake being the most "bloated" distro I use) is about 4 GB. But again, I don't run any servers, so I don't have to worry about Apache, databases, or expanding log files.

I have no idea if you can share /var between distros if it is on its own partition (this is where log files are usually kept), and while you can technically share a /home partition across distributions, I do not recommend it. It is also not recommended to install more than one distro to the same / partition (for ex-Windows users, this is essentially the same as installing two versions of Windows to the same C:\Windows or C:\WINNT directory, and as a Windows user, you should be able to guess what a nightmare that would be).

In general, I would suggest 5 or 6GB per distro for a "normal home user". This should leave you plenty of space for additonal software not originally installed by the distro that you come across later in the distro's repository. Don't forget, most of the programs/files that are going to be "clogging up" your drive are not going to live in the distro's / partition-- like Wine games that you might install, then uninstall, or media files that you might get more of-- so the / partitions don't really have to be "expandable". You just need enough space so that if you didn't originally install GNOME or OpenOffice, or Apache, or MySQL, you have space to install them later-- and by comparison to that 2GB NWN install, we're not talking about a great deal of space, even for all four of those together (probably around a quarter of that 2GB).

So if we're talking about 3 distros on a 40GB drive, we've used 18GB for the 3 distros, 1GB for swap (it's probably only 512MB, but I'm rounding this up to a full gig for the numbers, and maybe you're installing RH9, which will warn you if you don't allocate a real "2X RAM", so if you have 512MB memory, it really wants a gig of swap---!!!). So we've still got about 20GB left for the shared partition(s). Divvy that up however seems best to you (if you have to divide it at all). You might also choose to use only part of that 20 GB and leave some of it unpartitioned free space so you can expand one or more partitions later if you need to (you can do this "on-the-fly" with FAT32 partitions-- under Windows at least, possibly under Linux as well-- and you can also try doing that "on-the-fly" for Linux partitions by using parted, but I don't know how well that works out, never having tried it).

Important notes on partitioning a multi-boot that involves Windows

Do NOT let any of your Linux partitions be primary if you intend to boot Win2K or XP (or, gods help us, ME) alongside the Linux boots. Linux installers will normally auto-partition everything it can as primary partitions, but when you boot into Windows, good ol' Windows will try to identify the "new" primary partitions with the Add New Hardware Wizard in order to give them a drive letter. Windows can't understand Linux partitions, of course, so it will fail at this, but will keep trying. For every "foreign partition". Every time you boot into Windows. Insanely annoying. This doesn't seem to happen under 98 because 98 is good-naturedly stupid and just ignores what it can't understand (which is in this case A Good Thing). Linux does not need any of its partitions to reside on a primary partition (unlike Windows). All Linux partitions, including the boot and swap partitions, run perfectly fine from a logical partition inside an extended partition (and we're not making a separate /boot partition anyway), and if they are set up this way, Windows will just ignore them on boot.

Installing the distros

If you plan on running Windows beside the Linux distros, it is best if Windows is installed first. If you intend to run more than one version of Windows beside the Linux distros, the oldest Windows version must be installed before the newer Windows version, and then install Linux. This is to minimize bootloader problems. The Windows installer will always erase any bootloader that exists in the M(aster) B(oot)R(ecord), which contains the master table of what bootable partitions exist on the system. But a newer version of Windows will detect an older version and create a dual-Windows boot with it. Then Linux will detect that there is a Windows boot and create a dual-boot with that (choosing the Windows boot under LiLO or GRUB will take you to the Windows boot menu, where you can choose which version of Windows you want to boot).

If you have a third-party (Windows) bootloader that you would like to use (there may be 3rd party bootloaders for Linux, but I don't know what they are), you can simplify the whole bootloader thing immensely by opening its config utility after you have made your partitions and simply pointing each menu entry to the (empty) partitions that you will install each distro to. The entries will remain invalid until you actually install the distros, of course, but as soon as you do, you have a complete working bootloader. It is also possible to install Linux entries to the Windows bootloader if you have some twisted desire to do that. Instructions for this rather complicated process can be found at NT OS Loader + Linux mini-HOWTO, or more simplified instructions are at linux on the nt bootloader.

�Whether or not you plan to have a Windows install beside the Linux installs, you will mostly be installing each distribution normally. During the partitioning phase, choose "Custom" partitioning, skip any offer to use fdisk or cfdisk (you have already created the partitions, so you don't need to do it again), and point the installer to your pre-created swap and / partitions. Feel free to "initialize" (format) the / partition you've chosen to any filesystem you prefer (ext2, ext3, ReiserFS, JFS, XFS, etc). Write down the Linux designations of all partitions on your drive(s), especially noting which partitions that you install each distro to!! (meaning "Mandrake is on /dev/hdb7",� "Windows is on /dev/hda2", "the swap partition is /dev/hdb5", "the shared Linux partition is /dev/hdb9" or whatever your setup is). You will want this reference when you get to editing the various config files, if you need/want to wipe a specific partition for whatever reason, or need to mount the root filesystem of one distro under another to check something quickly without rebooting to that system.

When you get to the part where the bootloader is installed, tell the bootloader to install itself to the root partition of the distro -- except in the case of the last distro you install, which should install its bootloader to the MBR, unless you are already using a third-party bootloader, in which case install all of the bootloaders to the root partition of the distribution. Make a boot floppy for each distro.

This will affect the order in which you install the distros on a pure Linux box, to the extent that you may want the distro with the "prettiest" bootsplash/menu to be on the MBR, or if you prefer a specific bootloader, you probably want to install the distro that uses that bootloader last in order to have it on the MBR (most distros install LiLO, but many people feel that GRUB is easier to manage for this purpose, and a few distros do install GRUB rather than LiLO by default). You can usually find out which bootloader each of the distros you want to use loads on the distro's homepage (often somewhere in the package list, or the install instructions may well mention).

The only other thing you may want to do is create a "dummy" regular user (i.e. username:"dummy" pw: "junk") during the install, instead of the real one that you will commonly use. This relates to simplifying the process of sharing partitions, especially with mounted Windows partitions shared across the network, but is not necessary to share Linux partitions between distributions. Read the section on sharing partitions first, then decide if you want to do this.

Once you're done, you will only be able to boot into the last-installed distro unless you use the boot floppies you made or you set up a third-party bootloader as above. The first thing you want to do is fix that. Boot into the distro you can boot from the HDD. You can log in as root if you want, but it's probably better to log in as your normal user and su to root (and if you don't know what that means, you should probably stick to just one distro until you do, no offence :-P.

The theory here is that you want to open the config file for the bootloader and edit it to add the menu entries for the other distros you've installed. For LiLO, you'll want to edit /etc/lilo.conf. For GRUB you'll want to edit either grub.conf or menu.lst (apparently this can vary somewhat by distro or method of installation). I don't use GRUB myself, but the configuration files are in /boot/grub by default. General instructions for adding an additional Linux entry to GRUB and LiLO can be found here, about two-thirds of the way down the page, under the heading "LiLO and GRUB". These instructions are for adding an additional kernel entry for the same distribution already installed, but I offer it to give you a general idea of how to perform the editing (since you are essentially adding another kernel to the menu, after all). Another page with good info on configuring GRUB for multiboots (in this case, Linux and BSD) can be found here.� You might also want to take a look at Multibooting 101. It's not very detailed, though. MUO (MandrakeUser.org) also has a nice howto on configuring GRUB for multiboot, as well as an equally nice one for configuring LiLO. However, please see the GRUB manual or lilo.conf(5) for greatest certainty. If you use LiLO, don't forget to run 'lilo' or '/sbin/lilo' to set your changes!

OK. once you've got everything installed and booting from your bootloader, you'll want to set up the shared partition(s).

Sharing partitions between OSes:

Whether you're mounting/sharing a FAT32 or ext3 partition, the first thing you need to do is go to your user configuration. This is easiest done with a GUI tool, such as Mandrake's UserDrake, RedHat's User Manager, KDE's KUser, GNOME System Tools (one of which is a Users and Groups tool), or Webmin (to name all of the ones I can think of offhand), but can (as with all things Linux) be done via the command line as well. This is getting pretty long, so whether I'll cover the CLI method is anybody's guess. (Turned out, "Not." Sorry. :-( ) But if you're such a CLI jockey, you're not reading this anyway, so....

What we're about to do here:

The deal is that user ownerships/permissions are based on UID (user ID) and GID (group ID). Every user has a numerical UID and is associated with one or more numerical GIDs. Two users might have the same username (theoretically, I don't think you can actually do that), but different UIDs, thus would not be the same user. So you're going to want to know what your UID is, and you're going to want a special GID for a special group.

Why?

Because you (as a user) want to own mounted partitions across various distros, and possibly share them to the network. This means that you will want to mount them to your /home/username directory, because you only own files in that directory, and you can only share files from that directory. But when you mount these partitions using the special settings in /etc/fstab that I will tell you, they will acquire your normal UID and GID for that distro. Then when you boot into another distro, you won't be able to access the mounted files created under the first one, because they belong to a different UID or GID or both. To prevent this, we have to conform either the UID or GID or both across all distros. In the case of shared FAT32 partitions, I prefer to conform both UID and GID; for shared ext3 partitions, only GID is necessary.

So, here we are in the User Configuration Tool, to do just that. And yes, we will be doing both the User/Group Configuration and editing of /etc/fstab under each installed distro, so just assume that "rinse and repeat" is tacked on the very end of all this.

First, we're going to create a new group. Go to the "Groups" section of the tool and add a new group. Call it whatever you like (sharing, fileshare, scumsuckers, I don't care, it's your group :-D.) Note the GroupID of this group.

Special Note: Mandrake (and possibly other distros) provides an alternative way to create this particular group.Go to the Mandrake Control Center, then choose the Mount Points section on the left-hand side. On the right side, you should now see a tool that allows you to configure filesharing. Choose it and set file sharing to "custom". This will� create a new group called "fileshare". Close this tool and return to UserDrake to continue with the non-Mandrake people.
The following procedure is why you might have wanted a "dummy" user who will be deleted as soon as we're done with all this. Some distros make it very difficult to change the UID of a already-existing user, but allow you to use an "Advanced" button to choose the UID of a user that you create using the User Management tool (whatever one you use). So if you did create a "dummy" user (who you should currently be logged in as), use the tool to create a new one using your regular user name and password. Use the "Advanced" button or tab to specify the UID (this can be any unused uid-- and you will see several already used for various system services-- but it's easiest to just increment the "dummy" user's UID by one, since some distros restrict what numbers may be used for a UID). Make a note of the UID. Add the new user to whatever groups you need to be part of: wheel, users, audio, cdrom, etc. If you don't know, look at what groups the dummy user is part of, and add yourself to the same ones. Now add yourself to the new group that you just created (whether you did so manually, or through the Mandrake sharing tool), and change your default group to this group (so that all files and folders you create will belong to this group by default, rather than the "your_username" group). If you need an individual file or folder to belong to another group, you can change that on a per-case basis, so there's no harm in doing this.

If you're only sharing a native Linux partition across distros, you don't need to have made a dummy user during install, but you do need to add your regular user to the new group you just made. Then save, exit and continue to "Editing /etc/fstab". It's not that far away.

If you intend to share folders from these mounted partitions across the network to a Windows box, you may also duplicate those users on your Linux box now (using their Windows username and password), or create a common user account for them (if you prefer to do it that way), and add them to the new group as well. This does not actually share the folders (that's SAMBA configuration, not covered here), but it does ensure that you can add them easily to your sambausers list, and that they will have proper access when the folders are shared.

OK, we're done here for the moment. Save, exit, and on to part 2:

Editing/etc/fstab.

Why?
Because the "foreign partitions" (meaning pretty much any partition not in a native Linux format and/or not part of the main / filesystem) which are mounted via /etc/fstab are 1) by default mounted in places normally accessible only to root (/mnt/something or /something) and 2) always owned by root and the root group (unless you change that by editing this file). This is not really useful to you, especially if you need to share any of these mounted partitions back across the network or commonly need read-write-execute access to the partition's contents.

So what we're going to do now is tell Linux to mount these partitions in such a way that they are owned by you as a user under this distribution, and so that you will retain that ownership when you mount the same partitions under other distributions.

How?
Su to root and type "name_of_your_favorite_text_editor /etc/fstab" (without the quotes).

Here's a common (but totally fake) /etc/fstab:


/dev/hda1 ��� �/boot ��� �ext2
��� �noauto,noatime 1 1

/dev/hda2 ��� none ��� swap
��� sw 0 0

/dev/hda3 ��� / ��� ext3
��� noatime 0 0

/dev/cdroms/cdrom0 ��� /mnt/cdrom ���
iso9660 ��� user,noauto,ro 0 0

/dev/fd0 ��� /mnt/floppy ��� auto
��� noauto,user,sync 0 0

proc ��� /proc ��� proc
��� defaults 0 0

/dev/hdb1 ��� /mnt/win ��� vfat
��� auto,defaults 0 0

/dev/hdb5 /mnt/hdb5 ext3 noauto,users,exec 0 0

Remember where I told you to write down the designations of your partitions? Well, this is where it pays off.

Some distributions, like Mandrake, create an entry in /etc/fstab for every partition found (and in fact, under Mandrake, you could have done all this editing via DiskDrake during the install, but for your first time it's better to do it by hand and then feel "l33t" when you reinstall someday and can in fact set it up during the install because you know all the settings already ;-)).

Some distributions, like Libranet, create an entry in /etc/fstab only for Windows partitions found (and possibly only bootable Windows partitions, as opposed to non-bootable FAT32 partitions).

Many distributions do not create any entries in /etc/fstab beyond the /boot, /, swap, proc, and peripherals (/cdrom and /floppy). So you have to create entries for any other partitions yourself.

The fast explanation of how Linux designates partitions:

Partitions (as you hopefully already know) can be either primary or logical. Logical partitions are actually subdivisions of an extended primary partition, but they are not themselves primary.

Now, it's easy to understand that /dev(ice)/h(ard)d(rive)a indicates the first drive on your system (meaning that it's the on primary IDE controller, as master). But what about the numbers? Easy-- numbers 1-4 indicate primary partitions in order of discovery (you can only have four primary partitions on any given drive). Numbers 5 and up indicate logical partitions in order of discovery. So in the example above "/dev/hdb1" indicates the first primary partition on the second hard drive (meaning that it's on the primary IDE controller as slave-- if it was on the secondary IDE controller as master it would be designated as hdc and you can guess what it would be called if it was on the secondary IDE controller as slave, can't you?). If there was an entry for a FAT32 (or any type of) partition that was the second logical partition on the first drive, it would be /dev/hda6. And so on.

The fast explanation of fstab entries:

Each line of fstab refers to one device, on one line, in 6 sections. Each section of each entry must be separated by a space (though a tab is more common for readability's sake). There must be no spaces within a section.

Now, the only lines you should be editing or creating are those referring to mounted FAT32 partitions (or possibly limited editing of lines referring to NTFS partitions), and those referring to any additional ext3 partitions you may have made to hold shared Linux data. DO NOT EDIT THE LINES FOR /BOOT, /SWAP, / OR /PROC. EVER!!!! (unless you like killing your system).

The sections of a line are:


device designation/partition location



mount point



filesystem type



options

(lifted direct from the MUO Administration guide-- you might also want to read Mounting I) The last two options are flags for the file system utilities 'dumpe2fs' and 'fsck'.
The 'dump' field is either set to '1' (enable) or '0' (disable). Since 'dump' is used by backup programs for the ext2 / ext3 file system only, '1' is set just with entries for ext2 / ext3 media. All other media use '0'.

The 'fsck' field can either be set to '0' (disable file system check), '1' (check first) or '2' (check). '0' is set for all media with non-Linux file systems, removable and networked media, and virtual file systems. '1' is set for the '/' entry, since this partition has to be mounted (and thus checked) first and '2' for all other non-removable, local media with Linux file systems

So, since you cleverly wrote down your partition locations, you should be able to identify the correct lines in /etc/fstab, if they exist. If all the necessary lines do not exist (because you have more than one FAT32/NTFS partition and only one was picked up, or the shared Linux partition was not picked up), it is likely that one of the lines will be fairly close so that you can select and copy it, paste it to the bottom and edit it.

Let's get on with it:

example line 1 (FAT32):

/dev/hdb1 �� /mnt/win �� vfat ��auto,defaults 0 0

First thing we want to do is change that mount point to something more useable. If you need to share anything from this partition back to the network, it needs to be in your /home directory. I also find it more convenient to locate such a partition there even if I don't want to share it-- who wants to be browsing to /mnt when every file manager known to Linux opens in your ~/ by default? Thus "/mnt/win" becomes "/home/your_username/whatever_you_like".

Second thing we want to do is fix those options. Remember, no spaces in the options sections-- not even after the commas!

'auto' is fine if you want the partition auto-mounted on startup, which I would think that you do. If you have 'supermount' (because you use Mandrake, which uses this option by default, and/or see it on other lines, or because you compiled your own kernel and included it), you might want to use that instead, but opinions about supermount vary. In either case, it's one or the other, not both 'supermount' and 'auto'. If for some reason you want to manually mount the f(ile)s(ystem) every time you want to use it, take 'auto' or 'supermount' out.

The main thing we want to do is remove the 'defaults' option and replace it with:


rw,uid="#",gid="#",umask=#A#B#C

"rw" is read-write. Presumably you want this, unless the partition is NTFS (which you should not write to from Linux, so if it is, leave it as or set it to "ro" for read-only. Also, in the case of an NTFS partition, the 'vfat' section should read 'ntfs' instead).

"uid=#" and "gid=#" are the important options here, available only for vfat (and other msdos-type) partitions. This sets the uid (owner) and gid (group) to the ones you specify with "#". Replace # with your uid and the gid of the special group you created, and when mounted all files/directories will be owned by you and all members of the special group will be able to access it. How much access they have is determined by the next option:

"umask=#A#B#C". The umask option detemines how much permission you want to strip from the default. If you have heard of the chmod command, this is actually a sort of backwards mirror image of the same thing that command does, but no commands such as chmod, chown or chgrp can be used on the contents of mounted foreign partitions once they are mounted by /etc/fstab, either automatically or manually (I think you can use these commands if you mount a partition manually but bypass the fstab settings, but I'm not sure). So to change permissions or ownership of such partitions, you must use the umask option here in /etc/fstab.

The permissions are indicated by a 3 digit number, the first digit representing the owner, the second representing the group, and the third representing "others" who are neither the owner nor members of the group. The permissions are determined by adding together each number representing a permission: Read is 4. Write is 2. Execute is 1.

The default permissions for any newly created directory are 777-- r(ead,)w(rite,)(e)x(ecute) for owner, rwx for group, rwx for those neither owner or group members ("others"), because 4 +2+1=7. The default permissions for a file are 666 (rw, rw, rw).

However, you� might well prefer to give group members (presumably users over the network) less permissions than "absolutely everything", and you might very well prefer not to give "others" (whoever they may be) any permissions at all.

Each number in the umask subtracts that number from the default 777. So using a umask of 022 (which is the default umask if you don't specify one) would remove "write" permissions for both the group and "others" resulting in a default permission of 755 (rwx, rx,rx) for the mounted partition.. I myself use umask=007, giving full rights to me and the group (because I trust the members of my group-- I ought to, it's just me and my fianc�, who knows he had better bloody well not trash my PC "by accident" if he wants to live) and no rights to others (770). If you only want to give rw to the group, or maybe only read, it would be 017 (removing execute permission from the group and all permission from others) or 037 (removing write and execute permissions from the group, and all permissions from others)� to get a default of 760 or 740.
So, assuming that you want to automount this partition, want to allow users to mount and unmount it, your UID is 703 and you want to give execute permissions to yourself and read-write permissions to your group (whose GID is 368), the resulting line in /etc/fstab would look like this:

/dev/hdb1
��� /home/your_username/whatever_you_like
vfat ���
auto,users,rw,exec,uid=703,gid=368,umask=017�� � 0 0

��

When you eventually reboot (we have a couple of things yet to do before you do that), the partition will be accessible in your home directory, and you can share any of the folders inside the partition (or the entire partition) via Samba and the network user will be able to access (read) and write to it as if... it was a shared folder. Which is as it should be.

example line 2 (ext2/3 native Linux)

/dev/hdb5
/mnt/hdb5 ext3 noauto,users,exec 0 0

By now, you should have a fair idea of what this says. "The first logical partition on the drive set as slave on the primary IDE channel should be mounted to /mnt/hdb5, should not be mounted automatically, but may be mounted manually by a normal user, who may execute files (run programs) from this drive, which does not need to be checked/dumped at startup."

The only problem with this (other than the mount point, which is inconvenient, and the noauto, which may not be preferable) is that, when mounted, the files on this partition are going to be owned by root. And ext2/3 doesn't take the "uid=" option (that's only for vfat).

However, the ext2/3 filesystem does take the "grpid", or group id option. This is the one that makes this all possible. Grpid means that the mounted partition inherits the permissions of the group owning the mount point folder. So if the group you created earlier, added yourself to, and set as your default group, owns the mount point you're going to make very soon in your ${HOME} (which it will, because it's your default group), and that group has rwx permissions to that folder (which it should, but that's easily fixed if not), then you, o user, will have rwx permissions to all files and folders within that partition even though root still owns it.

It's beautiful. I looooove Linux. You can do almost anything you can think of. Before I started trying to create the Massive Multiboot, I thought that sharing a native partition across distros might well be impossible, especially since I had no idea how to do it. But that's why you should read your man(ual) pages, because that's where I found this (man fstab). And how great is it to know that I had this crazy idea (the same one you've had, or I wouldn't be writing this) and the OS supports you! It's already got a setting to enable your crazy idea to work without a hitch. It's truly wonderful.

So our second example line becomes:

/dev/hdb5��
/home/your_username/something_I_can_live_with_better_than_mnt��
� ext3 ��� auto,users,exec,grpid�� �
0 0

Are we done?

Not quite-- we need to make those mount points and delete the dummy user. Save fstab, exit the text editor and terminal, log out and log back in as your regular user. Head over to your /home directory (not far to go, since you'll be there as soon as you open a file manager) and create the necessary folders. Check their properties after creation and confirm the group ownership and permissions. Then fire up your User Management tool and delete the dummy user.

Now you're done... for this distro. Now, reboot, and you should have a choice of all available distributions/OSes (since we fixed the bootloader so long ago). You can boot into the distro you just left, to see how nice your /etc/fstab works, or you can boot into another, to set that one up. Let's do that...

Setting up the other distros
The procedure is basically the same, except that when creating the new "real regular" user and "special sharing" group, use the same UID and GID as on the first distro. There should be an option to specify this via an "advanced" button or right on the creation screen. This will prevent the dreaded "Owner: 468" property sheet entry (if you've created files or folders under the other distro, they are then associated with the UID of the creator. If this UID is not associated with a username when the partition is mounted under a different distribution, Linux will display the (invalid) UID rather than a username. If the GID is the same, and the group has rwx, you'll still be able to use the files, but it's ugly and annoying. IMHO.

It also means less numbers to remember when setting further distributions up if your Multiboot gets even more Massive (there's a lot of delicious distros out there, you might well want to "try them all!").

Last but not least (or, Shared Linux files)
Not much to say here; just a couple of notes. Like I said, since Firebird (for example) is an "extractable" rather than an "installable" you can easily extract it to the shared Linux partition so that you only need to have it once. However your user profile will remain in a hidden directory in your home folder. So two things: 1. install any extensions to your profile rather than the program directory (most if not all extensions allow you to choose) and 2) backup your bookmarks.html from the profile folder on the distro you use most often to the shared partition and use it to overwrite the others to keep your bookmarks roughly conformed when you boot into another distro. Yes, it's dirty, but it could be much worse. This goes for Mozilla as well.

Sharing a Mail folder under all distros using Mozilla or Thunderbird
This is extremely easy, and in fact works both cross-distro and between Linux and Windows (if the shared mail is kept on a FAT32 partition). Open MozMail or Thunderbird. You will be prompted to make a profile. Do that normally, but do not let it download your mail(uncheck the "Download Mail Now" box on the final creation screen. Yeah, OK, it still wouldn't download it without the password, but I like to be safe. I've moved all the way to another country and still have all my mail, so...just trust me ;-)).

In your file manager, create a folder in the shared Linux partition, or shared FAT32 partition if you want to use the same mail folder under Windows.

Interlude:
If you already use MozMail or T-bird under Windows and want to share the mail you currently have, then you will need to move the mail folder located in "C (or whatever drive you keep Windows on):\ Documents and Settings\your_username\Application Data\Mozilla (or Thunderbird, whichever)\profiles\your default profile (whatever it's called if you've made more than one)\random string of 8 numbers and letters\Mail\folder named the same as your incoming mail server. Move " folder named the same as your incoming mail server" in its entirety to the shared folder you created if youknow you've turned off� "Download mail on startup", which is turned on by default in both Moz and T-bird. If you have not turned this option off under Windows, reboot and do so before moving the Mail folder (otherwise one batch of mail will be automatically downloaded to a folder that no longer exists when you open MozMail/T-bird to change the folder location... which would be bad). If you use Mozilla, you should also export your address book to ldif before moving the mail folder, so you can import it into the various profiles of either Mozilla or Thunderbird under the various distros. Nothing more annoying than not having your nicknames installed when you're trying to dash off a quick email. End interlude.

For all versions of Mozilla and T-Bird (both Linux and Windows), go to "Mail and Account Settings" (in MozMail under the Edit menu, in T-bird under the Tools menu). Under the "Server Settings" section, at the very bottom of the dialog, is the "Local Directory" setting. Change this from the default to point to the folder on the shared partition (type in the complete path). Now close and restart Thunderbird, or close Mozilla completely and reopen it, and then the Mail component (if you don't start MozMail with the -mail switch).

MozMail/T-bird� will ask for your password (because it likes to download mail on startup). If this is a completely new mail collection (you aren't conforming with previously downloaded mail), then go ahead. If you moved a Windows mail folder, imported mail from another mail client or basically did anything that means there should be old mail displayed, cancel and check to make sure that the old mail is in fact displayed properly before adding new downloaded mail to it.

This sounds very complex, but it's really not, and the best thing is that if you create mail filters under any distribution, the fact that the mail folder is pooled means that they will work without a hitch (well, without any more of a hitch than MozMail and T-Bird usually have, which isn't much) under all distros (and Windows).

OK, that's really it. Sorry it's so terribly long and unpretty, but I hope it helps those of you wanting to set up a Massive (or Not-So-Massive) Multiboot Linux system.

Have fun!

�2003 Holly Bostick (motub).

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