Re: Mounting USB drives on a "read-only-rootfs" based system

From: Jeffrey D Boyer <Jeffrey.D.Boyer@jci.com>
To: Mike Looijmans <mike.looijmans@topic.nl>,
	Christopher Larson <clarson@kergoth.com>
Cc: "yocto@yoctoproject.org" <yocto@yoctoproject.org>
Subject: Re: Mounting USB drives on a "read-only-rootfs" based system
Date: Wed, 15 Jun 2016 13:14:08 +0000	[thread overview]
Message-ID: <a99347d5dc6f4d219af8fe6cb72f8de6@BN3PR97MB0132.062d.mgd.msft.net> (raw)
In-Reply-To: <57610CB8.4050904@topic.nl>

My distro is running udev.  I discovered the automounter script in /etc/udev/rules.d was causing the mount point to be /media.  For all I know, this is default behavior for udev.

Anyway, I think I found a solution.  As suggested by another person on the thread, I went ahead and mounted a tmpfs on the /media directory.  This allowed the udev automount script to function as it did when the squashfs option was disabled.  

Thanks to everyone for all the help.

-----Original Message-----
From: Mike Looijmans [mailto:mike.looijmans@topic.nl] 
Sent: Wednesday, June 15, 2016 4:07 AM
To: Jeffrey D Boyer <Jeffrey.D.Boyer@jci.com>; Christopher Larson <clarson@kergoth.com>
Cc: yocto@yoctoproject.org
Subject: Re: [yocto] Mounting USB drives on a "read-only-rootfs" based system

On 14-06-16 15:48, Jeffrey D Boyer wrote:
> Sorry, /media is not a symlink and there is no /run/media link or directory present on my running system.  When I insert an SD card, for example, I get a bit of text on the debug serial port that a card has been detected, but I don't see a mount point anywhere after that.
>
> 	root@mySys:/# mmc1: new high speed SDHC card at address 1234
> 	mmcblk1: mmc1:1234 SA04G 3.63 GiB
> 	 mmcblk1: p1
>
> It should be noted that if I exclude the " read-only-rootfs" option in 
> the bb script, a normal read/write kernel image is produced and the 
> action of inserting an SD card under those conditions will 
> automatically produce a mount point at /media/mmcblk1p1

Apparently your distro or image or whatever is lacking some directories. The /run/media should have been created automagically.

Are you using udev or mdev for hotplug?

For mdev, I implemented the automounting using /run/media and that should also work on read-only-rootfs systems. So I can probably figure out what's wrong with your config.

For udev, I don't have a clue, sorry...

> FYI, I'm running 3.14 kernel.  Is this a job for aufs?  If so, how would I go about configuring it?

No, it's not related to autofs or aufs or whatever. It's plain simple udev or mdev.

Kind regards,

Mike Looijmans
System Expert

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