linux-kernel - Re: How can I add "busybox sh" as init during boot of the custom kernel?

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Message-ID: <89f666dc-e7b3-44ad-846c-b1f1ee278940@infradead.org>
Date:   Sun, 22 Oct 2023 18:59:42 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     gmssixty gmssixty <gmssixty@...il.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: How can I add "busybox sh" as init during boot of the custom
 kernel?

> On Mon, Oct 23, 2023 at 6:15 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>>
>>
>>
>> On 10/22/23 16:56, gmssixty gmssixty wrote:
>>> How can I add "busybox sh" as init during boot of the custom kernel? I
>>> have compiled the kernel and put the bzImage in /dev/sda3 (/mnt/sda3).
>>> Booted that kernel. After booting, I got a message to set the init
>>> process. I have put the busybox in /bin. Now I want to add this
>>> "busybox sh" as an init process. How can I do this?
>>>
>>> Note that, I did not install any other software in that /dev/sda3
>>> (/mnt/sda3). I have only bzImage and busybox.
>>
>> from Documentation/admin-guide/kernel-parameters.txt:
>> (or https://docs.kernel.org/admin-guide/kernel-parameters.html)
>>
>>         init=           [KNL]
>>                         Format: <full_path>
>>                         Run specified binary instead of /sbin/init as init
>>                         process.
>>

On 10/22/23 17:34, gmssixty gmssixty wrote:
> I tried this: init=/bin/busybox sh, but it got Kernel panic and
> failed. On the other hand, what should I write in /sbin/init?
> 

Please don't top-post.

You need a file name after init=.
"/bin/busybox sh" is not a file name AFAIK.

To use /sbin/init, enter
	init=/sbin/init

To use bash (e.g.), enter
	init=/usr/bin/bash

The kernel init code already tries to use /sbin/init if that file is
present, along with /etc/init, /bin/init, and /bin/sh .

-- 
~Randy