which partition did i boot from?
 

A bunch of drives exist on my system with a bunch of OSes. It's late at night and I forgot which partition i booted from. Is there an easy wy to figure this out? fdisk -l gives me all the partitions but how do i know which one i booted from?

or just

if they use UUIDS you can then


to see which partition the uuid is linking to

Do you have Gparted? It shows graphically which OS is on what partition. Like when I look at Gparted on mine I see that /dev/sda1 is Dreamlinux, and it occupies a little over 20Gigs.
So if I am using Dream I know I am on sda1.

If you have it, it should be listed in Administration. Just click it and it should load the GUI. At least that is what I do.

Hope this helps, Good luck.

EDIT: Never mind, tried the df -h that andrewthomas posted and that is much quicker. :)

tnx andrewthomas.

btw, i tried gparted but it doesnt say which parttion is the boot partition of the 12 that it sees on 2 hard drives and 2 usb sticks

You are welcome.

Do you still seem to have a problem?

cat /etc/fstab would've done itr also as andrewthomas pointed out

the mount command without any options shows what devices are mounted and where, so the device mounted at / should be the partition you mounted.

None of the answers provided address the question asked.
AFAIK there is no way to tell.

Indeed; if you are multi-booting, then the current root '/' dir does not have to be on the disk or partition you actually booted from to start with ...

Unlike Windows, Linux does not make file system device names dependent on the boot file system so flamelord's answer is as good as it gets -- unless you want to know which MBR was executed and which file system was used by a boot manager such as GRUB or Lilo.

The OP question would be more meaningful under Windows where the system drive becomes C:. The question would be "Which partition is the C: drive on"?

I guess I'll ask a question.
If I use cat /etc/fstab doesn't it only tell you about specific mounts of that os?
I understand that you can add to fstab, but in my case fstab doesn't show windows os which resides on same hdd.

I don't have as many drives, but I have a number of partitions in my comp. I've found that if I open gparted, and right click on all the different partitions, only the one that you are using as your / will NOT have a "Delete" or "Resize/Move" option highlighted. All the other partitions will have this option. Also if you try to unmount it, gparted will throw up an error.
I guess it's not the simplest way to do things, but if it helps.................

I guess that I missed the point of the question.

You want to know about which bootloader loaded the OS that you are on.

Well, the best source of information about bootloaders is

http://bootinfoscript.sourceforge.net

It is best to run it from a LiveCD to be safe.

Fire up a LiveCD and navigate to the above link and post the results with your reply.

Then you can look at the output of

when you actually boot from a HD and know conclusively where you booted from.

For multiboot I could think of the "uname [-r]" command and the "find" command to search for any "bzimage*" "-o -iname \"vmlinu*$KERNELVERSION*\"" .

Also to "grep" for the $KERNELVERSION in the "/boot/grub/grub.cfg" or menu.lst .

Grub actually loads the kernel .

[edit]
The boot_info_script.sh is quiet interesting 3000 lines long .
Note : needs to be "chmod 0755" to become executable .

Because I have 12 partitions on the main drive , I have 12 long menu.lst in the RESULTS.txt file .
Because I have a wrapper script for the mount command I can say for now : It mounts every partition and looks for kernels and grub-files .
Thanks for posting the link !
It is much more sophisticated , than the thoughts I posted .
[/edit]

Nope.
You can make some presumptions (as you have), but from a running instance of a system, there is no way to *know*.

It's even possible the instance wasn't booted from a partition at all - that is what kexec provides.

If you have disk utility it will atleast let you know which partitions are mounted though, as it will offer the option to unmount partition. Screenshot of disk utility.