Truly silent boot [SOLVED]

[JKosta]

I want to get rid of the following output when kernel is loading:

early console in decompress-kernel
Decompressing Linux . . . Parsing ELF . . .done
Booting the kernel

Anybody knows how?

[NeddySeagoon]

JKosta,

Patch the kernel to remove those text ouputs.

Use gep to find the strings in the kernel source.

[JKosta]

NeddySeagoon,

Can you detail?
Thanks.

[NeddySeagoon]

JKosta,

I will do an example here ...

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roy@NeddySeagoon_SSD ~ $ cd /usr/src/linux
roy@NeddySeagoon_SSD /usr/src/linux $ grep -R Decompressing

Searches the entire kernel for the word "Decompressing" with a capital D.

In my kernel, the output is

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Documentation/xz.txt:    is used in single-call mode. Decompressing the kernel itself is an
arch/alpha/boot/bootpz.c:	srm_printk("Decompressing the kernel...\n"
Binary file arch/x86/boot/compressed/misc.o matches
arch/x86/boot/compressed/misc.c:	debug_putstr("\nDecompressing Linux... ");
Binary file arch/x86/boot/compressed/vmlinux matches
Binary file arch/x86/boot/vmlinux.bin matches
Binary file arch/x86/boot/bzImage matches
Binary file arch/x86_64/boot/bzImage matches
arch/m32r/boot/compressed/misc.c:	puts("\nDecompressing Linux... ");

We can ignore the binary files as they are not source code.
We also ignore Documentation/, as that is human readable instructions.
This leaves three files ...

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arch/alpha/boot/bootpz.c:	srm_printk("Decompressing the kernel...\n"
arch/x86/boot/compressed/misc.c:	debug_putstr("\nDecompressing Linux... ");
arch/m32r/boot/compressed/misc.c:	puts("\nDecompressing Linux... ");

The first one is for DEC Alpha based sysems, the second one is for Intel/AMD based systems.
I don't know what m32r is.

Open the file in nano

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nano -w arch/x86/boot/compressed/misc.c

Notice the file starts with lots of comments that are started with /* and ended with */
Press Ctl-W in nano to search and enter

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Decompressing

to search

At the end of the file there is

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        debug_putstr("\nDecompressing Linux... ");
        decompress(input_data, input_len, NULL, NULL, output, NULL, error);
        parse_elf(output);
        debug_putstr("done.\nBooting the kernel.\n");
        return;

Add the comment marks around

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 debug_putstr("\nDecompressing Linux... "); 

and

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debug_putstr("done.\nBooting the kernel.\n");

so it reads

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/*        debug_putstr("\nDecompressing Linux... ");  */
        decompress(input_data, input_len, NULL, NULL, output, NULL, error);
        parse_elf(output);
/*        debug_putstr("done.\nBooting the kernel.\n");  */
        return;

These lines of code are now comments and will not be compiled when you rebuild the kernel.
You could also just delete the lines but comments are easier to reverse.
You can also add a comment of your own for you to read later.

That is the method with a worked example.

[JKosta]

NeddySeagoon,

I've followed your example and it worked!
Thanks a lot!

[666threesixes666]

is there a way to automatically patch any kernel that comes past me so i can run a command instead of digging through files by hand? how do i tell openrc shush too?

[NeddySeagoon]

666threesixes666,

Building on the above example, you can make a patch file and run patch < patchfile to apply your patch.

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man patch 

tells how to use diff to make a patch.
If the package of interest supports epatch, you only need drop the patch into the right place in /etc/portage and portage will apply it for you.

For openrc, file a feature request for a silent USE flag. Of course, patches welcome.

[Lukas0907]

Hi,

instead of patching the kernel you can also simply disable CONFIG_X86_VERBOSE_BOOTUP which does the same thing (Linux 3.13).

Cheers,

Lukas