multi linux boot
 

I have been using mandrake for about a week now and i would like to reinstall it along with two other linux distros. I am going to repartition my HD so that the 3 distros can use those directories which can be shared between one another but i would like to know if i am doing this correctly.

I plan to partition as follows:

/boot 20M
/ 500M
/usr 5G
/usr/local 15G
/home 15G
swap 1G
/tmp 500M
/var 1G


For the time being i wont be running any servers but i will likely be doing so in the future. If any partition sizes are out of wack please let me know.

My concern is this. Which partitions can i share between the 3 different distros of linux? My understanding of linux isnt so comprehensive but i believe that i can share /boot /home swap and /tmp. If any i listed cant/shouldnt be shared or if any other can be i would appreciate it if you let me know.

Thanks

I'm far from an expert but I'll try to give you a reply :)

/boot 20M -- I think most distributions suggest a /boot of more than 20 Megs, and You could just install to the MBR if you want to save a partition.

/ 500M -- You will need a / partition for each distro, otherwise they will basically be one big distro.

/usr 5G -- this will be fine if you wanna all your programs and such installed for all three distros and assuming all three have the same libraries installed and such, I'm assuming the point of three distros is for three seperate OS's not 3 ways of accessing the same one...

/usr/local 15G -- same as above, unless you have a good reason for sharing/separating stuff in /usr/local I'd just leave it as part of the / partition for each distro.

/home 15G -- this is a good one to share, 15 Gigs is only needed if you will have a lot of data or programs you download w/ non-root access to be held here. Or if you install from source (.tar.gz) files and unpack them in /home.

swap 1G -- do a "free -m" in your mandrake distro right now when you have a few programs running to see if you actually need a gig of swap...the important numbers are those w/out the cache and buffers. You may not even be using your swap partition right now. But it will share fine if you want.

/tmp 500M -- not sure at all why you would make this it's own partition...again I'd say this is better left as part of the / partition for each distro.

/var 1G -- don't know bout this...sorry

Over all I'd suggest this scheme for you. if you have a 40 gig harddrive which I think you do.

/ for first distro -- 11 G
/ for second distro -- 11 G
/ for third distro -- 11 G
/home -- 6 G
swap -- 500 M
/etc -- 500M (check your mandrake install and times it by 3 and add a little to be safe)

having a /etc partition will allow you to keep a lot of your customizations alive even if you switch distros again, plus it will make all distros configured more or less the same. It is not needed though. Hopefully I am not way off here, if I am someone please help his poor soul :P

I am not an expert either and probably do not do everything the best way but, I do have several operating systems on each of my two computers at home. On this computer I have PC-DOS 2000, Windows XP, Slackware 9.1 Linux, Vecter Linux 4.0, Fedora Core 2 and Red Hat 9. I use the same /home directory for each distro. That way, everything in my home directory is available no matter what I happen to be running. If for some reason, I need to reinstall a copy of Linux, the files in my home directory safely in a different partition. When installing Linux, the installation program always asks me if which partitions need to be formatted. Obviously, I choose not to reformat my /home partition because I want to preserve the data that is already there. I also use the same swap file for each copy of Linux and allow it to be reformatted each time I install another copy of Linux. The swap file is on a separate partition. If I remember correctly, they usually recommend that the swap file be twice the size of the amount of ram that the computer uses.

I question the sizes of your partitions somewhat. I looked just now on my older computer to see how much my copy of Red Hat 8 is using for each directory that you mentioned. Most of directories on my computer are not seperate partitions but the sizes of what is in them would probably be similar. So here is how much is stored in each of my Red Hat 8 directories:

/usr has 2.4 Gigabytes in it
/usr/local has 3.2 Megabytes in it (notice that is MB not GB)
/tmp has 28 Kilobytes in it (notice that is KB not MB or GB)
/var has 52 Megabytes in it (notice that is also MB not GB)
/boot has 5.0 Megabytes it is (yes, that is also MB not GB)
/home 70 Megabytes in it

So on that computer /usr has a lot in it while most other directories have relatively little in them. It is different in the copy of Slackware 9.1 on my my newer computer, it now has 16 GB of space used in my /usr/local/vmware directory. The /usr/local directory was almost empty until I decided to install Vmware and create several virtual machines in there. Just for comparison when running as root (or after using the "su" command) you can use this command to see how much is in your /usr/local directory:

du -sh /usr/local

If you will be using several versions of Linux it might be best to use a separate /boot partition. It is not really necessary but, because some of what is in there will be shared by several of the operating systems, it might be best to keep it seperate. In my "/boot" I have a different kernel in there for each version of Linux that I use. My knowledge about kernels, bootloaders and the /boot partition is very limited so I may or may not be doing it the best way. On my older computer I have Partition Magic installed. I used Partition Magic to resize the various partions after I realized that some were nearly full and others were almost empty.

My two computers are only used at home. On important servers, the /home and one other directory is sometimes placed on a seperate partition just so the computer can keep working when the partition unexpectedly becomes full due to things that users or hackers have done. Is the /tmp folder the other one that is sometimes placed on a separte partition for that reason? I am not sure.

By the way, the install program for Slackware has problems if there are more than a total of about 15 or 16 Linux partions on both of my hard drives. So if you plan to use Slackware you should probably install it before you exceed that limit. Slackware will run fine with more partitions than that but at times the install program has problems in that case. This has happed on both computers with several different versions of Slackware so I do not think it is just a problem that is specific to my computer. Even when the problem occurs I can still install Slackware, I just need to type blindly and realize that what I am typing and other information is not being displayed.

Since you seem to be a newbie I will add one more thought. Once you create your various partitions you only need to type this to get a list of which partitions are mounted and how full each partition is:

df -h

Well, I will add one more comment. Most Linux users probably just have three partitions on their computer. They have a Windows fat32 or NTFS partition, a Linux "/" partition and a Linux swap partition. That way they avoid having some partitions that are nearly empty and others that are nearly full. Many Linux users disagree on how best to partition things. It sounds to me like you are planning to create more partitions than is necessary.

There is a good how-to over on distrowatch on installing multiple distributions. They've made some comments about which partitions can and can't be shared.

John

/home, /tmp, swap can be shared without any problems.

You can share /usr/local too if you stick to the above partition. You will need to be careful though.

The distrowatch link that jkobrien provided describes setting up the boot loaders in a way that is entirely different than what I said. Perhaps that is better than the method that I vaguely described. It is somewhat like how I do it on my older computer except that in that case I installed the System Commander bootloader and allowed it to overwrite the Master Boot Record (MBR). When installling each version of Linux I always choose the option to install LILO (or GRUB) to the root sector of the boot partition instead of to the MBR. When starting the computer the System Commander bootloader would ask me which OS I wanted to run. If I choose Red Hat 8 it would then start up the LILO bootoader that was on that partition. Setting it up either way was much easier than I am making it sound and I originally did it as a newbie. I am not sure which method is the "typical" way of booting multiple copies of Linux.