From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mark Lord <kernel@teksavvy.com>
Subject: Re: [PATCH] Syscalls: reboot: Add options to the reboot syscall to
 remount filesystems ro
Date: Thu, 03 Mar 2011 13:29:53 -0500
Message-ID: <4D6FDE21.7000303@teksavvy.com>
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Cc: Ken Sumrall <ksumrall@android.com>, linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>,
	Matthew Wilcox <matthew@wil.cx>,
	Eric Paris <eparis@redhat.com>,
	Dave Young <hidave.darkstar@gmail.com>,
	Jiri Slaby <jslaby@suse.cz>, James Morris <jmorris@namei.org>,
	linux-fsdevel@vger.kernel.org
To: Linus Torvalds <torvalds@linux-foundation.org>
Return-path: <linux-kernel-owner@vger.kernel.org>
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On 11-03-03 01:17 PM, Linus Torvalds wrote:
> On Thu, Mar 3, 2011 at 9:45 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> How many mounted filesystems do you have that it's so hard to keep track of?
> 
> Btw, /proc/mounts will track them for you even if you don't have a
> 'mount' binary that does.
> 
> Parsing that is pretty trivial. If you have spaces or special
> characters in your pathnames (you may control the mount paths, you may
> not - I have no idea), you'll need to be able to handle the escape
> format (\oct). But other than that, it's literally just
> 
>  - read all of /proc/mounts into a buffer
> 
>  - for each line, split by space, and you'll have the directory name
> right there in the second field
> 
>  - do the unescaping ("\oct" -> character) if needed. It's good
> practice. Test it.
> 
>  - just do a read-only remount on it.
> 
> All done. No kernel changes necessary. It just works.


This might be much less complex:

   #!/bin/sh
   echo s > /proc/sysrq-trigger
   echo u > /proc/sysrq-trigger