Red Hat

If I create some hard disk partitions: /boot, /, /usr, /tmp ... , of cause the kernel is in the /boot partition, /etc/fstab is in the / partition not in /boot partition, when the system boot, how does the kernel know where is the / partition?

Or I create a separated partition: /etc, can the kernel find /etc/fstab in the booting time?

Thanks.

/etc MUST reside on the root partition. If you move /etc/ to another partiton, assuming the OS lets you, you will have a non functional machine.

The basic quick and dirty of it is this:

Inside the Linux boot process

The bootloader then needs to know where your kernel and when the root filesystem is.

/boot does NOT have to be a filesystem. It can be a directory on the root partition. You should have a look at this:

http://www.pathname.com/fhs/

Thank you!

But:

/boot does NOT have to be a filesystem. It can be a directory on the root partition.

I have done it before. In fact, many net-friends suggest let the /boot be in a separated partition(ext2/ext3...).

Yes, you can do so. The kernel really doesn't care. As long as the bootloader can access the files it needs to bootstrap the kernel into memory, the system will boot. I've had situations where I accidentally made my kernel without ext2 support, causing an odd situation where the kernel could boot but couldn't mount /boot, preventing me from updating the kernel! Oops.

Any partition not necessary for very basic system services can be made a partition, notably things like /opt, /usr, and /home.

In the past, there had been a reason for this: the 1024-cylinder-limitation of the bootloader LILO (prior to version 21.x).

OK, thank you every one, it is my English comprehension problem, I misunderstanded " /boot does NOT have to be a filesystem ", I am so sorry for wasting everybody's time.

Thread close.

There's other good reasons for it, too. Keeping it separate means you can keep it an old-fashioned ext2/3 filesystem, compatible with grub, while you can use whatever filesystem you want for root without confusing grub. It also makes it a lot harder to damage by accident.