Managing multiple boot partitions

Question

HI,
I Have multiple boot partitions on my mac pro. 1 mountain lion and 1 snow leopard. is there any way to make disks read only to the other bootable partitions?
so for example, when im in one of my snow leopard I dont want snow leopard to be able to write to my mountain lion and vise versa. Please let me know.

Answer 1

iJny9956: Ok.  I'll walk you through this best I can over the web.  You'll need to go through the whole process twice—once for each OS.
1) Boot into one of your operating systems.
2) Log into an Admin account
3) Launch "Disk Utility"
4) Select the drive or partition containing the operating system you want to make read-only (so, if you're booted into Mountain Lion (ML) select the Snow Leopard (SL) partition, and vice versa)
5) Get Info… on that drive or partition by using the Command-i keystroke, or File > Get Info
6) In the window that appears, look for the line beginning, "Universal Unique Identifier".  The long string of numbers, digits and dashes after this is the value you'll need for fstab.
7) Select this long string, excluding any spaces at the beginning or end, and Copy it.
8) Now launch Terminal—you'll find it in /Applications/Utilties, alongside Disk Utility
9) Type: sudo vifs
10) Hit Enter.  You'll be presented with a warning if you haven't used sudo before, and then a prompt for a password.
11) Enter your Admin password.  You'll receive no visual feedback of the characters you enter—this is normal.  Hit Enter.
12) You've now entered a command-line text editor called vim, which has in turn opened the fstab file for you to edit.  This is the only recommended way to edit the fstab file, as the text file itself will say.
13) Use your cursor keys and move the cursor to the empty space below the warning text.  Press the letter "o" on your keyboard.  This will open a new line below where your cursor was, and allow you to enter text.
14) Enter the following text—each entry on the line should be separated by a single space, as I've done here:
UUID=XXX-XXX-XXX-XXX-XXX none hfs ro
Instead of entering the "XXX…"s, paste in the value you copied from Disk Utility.  Make sure there is no space between the "=" and the start of the value you paste.  "none" means the disk or partition should be mounted to the default location, so you can ignore this; "hfs" defines the filesystem being used on the disk or partition; "ro" is the variable that means, "read-only".
15) That's it.  Press Escape once, then type a colon:
You'll see this colon appear at the very foot of the Terminal window.  Now type:
qw
These stand for "quit" & "write".  Hit Enter, and the text editor will save and quit.
And that's it.  If you reboot your Mac Pro at this stage and boot into the same OS you were just working in, you should find that the other OS's drive or partition is now read-only.  You can confirm this, after you've rebooted, by launching Terminal again and typing:
mount
Hit Enter, and you'll see a list of all your mounted devices.  Some you won't recognize, but you should see that the line referring to the other OS's drive will have, "read-only" next to it.
Now, just repeat for the other OS, and you should be done.  If you have any questions, post back here.  NB: to stop the other OS's drive mounting at all on boot, replace "ro" in step 14 above with, "noauto".  If you want to use more than one variable here, separate them with a comma but don't add a space—eg.:
ro,noauto,noexec
In this example, a drive will not be mounted on boot, but when it is explicitly mounted (eg. with Disk Utility) it will mount Read-Only, and with the ability to launch programs stored on that drive removed ("noexec").  This latter can be useful if you use Spotlight to launch applications and don't want to accidentally launch an application on the other OS's drive.
HTH.
PS: I was in a hurry and didn't proof-read this.  Any questions, just post back.