When I boot linux to Altera DE1 with dts file de1.dts (attached below), I have an error: bootconsole [uart0] disabled
bootconsole [uart0] disabled
NET: Registered protocol family 17
Warning: unable to open an initial console.
devtmpfs: error mounting -2
Freeing unused kernel memory: 1424K (c02f8000 - c045c000)
Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
Someone please tell me what caused this error? I'm looking for a solution. :(
The full terminal result is here: http://pastebin.com/8yDAxX5y

You need a valid linux executable in /init (check your initramfs image). I recommend that you get your kernel working in or1ksim and then try running it on the board.

Sorry, but would you mind making it more clearly how to do that? I'm just feel your answer is a bit hard to understand to me.

First of all, your problem most likely is not connected with OpenRISC. You can google your error and results for ARM/MIPS/etc will be still useful. So google "kernel panic - not syncing attempted to kill init initramfs" or something.

I'm assuming you are using Jonas Bonn's linux tree (look at your "git clone" command). This means you have some pre-compiled rootfs with BusyBox image located at arch/openrisc/support/initramfs of your linux source tree. It might be that 8 MB RAM is not enough to fit that exact busybox image. Try replacing arch/openrisc/support/initramfs with a textbook "hello world" elf binary from the attachment. Recompile your kernel with that and see how it runs.

Here is the source code.