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Since Android is powered by a Linux kernel it should support booting in single-user mode.

Which version of Android supports single-user mode and how is one able to start an Android device in this mode? Any references?

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migrated from security.stackexchange.com Jul 14 '12 at 9:18

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Android boot loaders don't tend to expose the functionality of changing kernel command line parameters, also single user mode would need a serial terminal or similar for input. –  ewanm89 Jul 14 '12 at 10:07

3 Answers 3

As per a brief introduction

Single user mode, also referred to as maintenance mode and runlevel 1, is a way of running Linux or another Unix-like operating system that uses minimal system resources and provides only minimal functionality.

Single user mode can be useful for checking and repairing operating systems, particularly those that have been damaged and will not allow booting (i.e., starting up) into the default GUI (graphical user interface) or console (i.e., text-only) multi-user mode.


Source: The Linux Information Project - How to Change to Single User Mode


To answer your question

With Android, the equivalent of a low runlevel, as to perform critical operations with minimal system resources, is rooting.

From the Wikipedia - Rooting (Android OS):

As Android was derived from the Linux kernel, rooting an Android device is similar in practice to accessing administrative permissions on Linux or any other Unix-like operating system.


References:

Since what you are actually seeking is a way to root your device and gain the maximum allowed privileges over it, you can refer to this links:

Internal links

External Links

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2  
rooting != single-user mode –  Flow Jul 14 '12 at 19:17
    
Well the down vote didn't came from me. You put some effort into researching the "rooting" topic. Make clear that you think that rooting is the closet to single user mode. Nevertheless I think that this isn't the right answering approach, that's why I didn't upvote it. But in general, your answer has everything that good a SX answer should have, that's why I didn't downvote. –  Flow Jul 14 '12 at 22:02
    
No problem. Your answer is not completely wrong. I even get your point. The problem lies within the question: People tend to assume just because Android uses the Linux kernel that it also uses everything else which they know from debian/ubuntu. –  Flow Jul 14 '12 at 22:16
    
I've deleted cluttering comments. Also rephrased the answer as to clarify the original content. –  Zuul Jul 14 '12 at 23:43

IIRC, there is a equivalent of a single mode in Android, when powering up, hold down the menu key, Android boots into 'Safe mode' a lá Windows Safe Mode. This will vary with manufacturers and their Stock ROMs.

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Single user boot is a feature of the init daemon (initd, like sysVinit) and not the Linux kernel. Since Android only shares the kernel with Linux and not the init process, a genuine single user boot can not be achieved.

Android has something that is called "Recovery Mode", but it's not exactly the same as a single user boot on an Unix system. The approach of recovery mode on Android is different because instead of trying to repair the bricked/broken system, on simply can re-flash the ROM or perform a factory reset, which will hopefully restore the systems functionality.

About the init used: Android uses just a script called init.rc, which gets started by the kernel and is used to start further services. You can view the current source of init.rc here. It supports no runlevels.

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@Zuul updated my answer –  Flow Jul 14 '12 at 22:18
    
Thanks for the question update, extra documentation to a better clarification on the subject at hand is always welcome. +1. –  Zuul Jul 14 '12 at 23:46
    
The recovery is a pretty direct analog to an installer boot disk - it's a complete, self contained miniature Linux system (using android libraries of course). –  Chris Stratton Jul 15 '12 at 6:56
    
Well, it seems that there are a number of software modules that have been tested on various versions of Android in "single-user mode". If there is no single-user mode for Android why are there vendors like Samsung and Cisco claiming Android single-user mode and not "recovery mode"? –  Drew Lex Jul 17 '12 at 21:46
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That "single-user mode" is also stated for Windows OS on that site. So I would guess that they refer to something different when speaking of "single-user mode", since Windows does not use SysV init. The term itself is not accurate. If I refer "single-user mode" I mean the runlevel 1 of a SysV init. –  Flow Jul 17 '12 at 22:24

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