Also this is outside the realm of the SDK (running as the system user is
*way* outside the realm of the SDK), so would best be asked on an
appropriate group like android-porting.
On Fri, Nov 5, 2010 at 9:12 AM, Chris Stratton wrote:
> You cannot read USB devices anyway as android does not, without
> platform modifications, support USB host mode.
>
> You can of course read the SD card when it is *not* mounted over USB
> to an external computer but is instead mounted locally by android,
> provided that your application is not running as the system uid.
>
> You should not need the system uid to *read* files under /system/lib -
> indeed, a lot of them are already memory mapped into your application
> when it is forked off of zygote. However, you should be aware that
> with few exceptions most of those files are considered unstable,
> private APIs and so should not be directly utilized by your
> application but only by intermediate java layers of the platform which
> present the public APIs to you.
>
> If for some reason you really needed to be the system uid and also to
> access the SD card, you would need to either use inter process
> communication between something that is the system uid and something
> that isn't which is accessing the SD card, modify the platform to
> remove the restriction on the SD card and the system UID, or run as a
> privileged user other than the system uid.
>
> On Nov 5, 11:32 am, xhy wrote:
> > Thank you sir，I want to visit the file which is under the
> /system/lib,But
> > at the same time,I also want to read the USB device.So what can i do ?
> >
> > 2010/11/5 Chris Stratton
> >
> >
> >
> > > If the sdcard gets unmounted, any process with an open file handle to
> > > it gets killed.
> >
> > > Letting the system process be killed was considered a bad thing. To
> > > avoid that, the system process (which is to say any system process) is
> > > not allowed to access the SD card.
> >
> > > FYI, you probably will not be able to install your apk with the system
> > > uid on most secured devices, unless you are in possession of the
> > > system certificate for the devices on which you want to deploy.
> >
> > > What exactly do you need to access in the /system folder? You do know
> > > it's mounted read-only, right?
> >
> > > Technically, anything regarding the system folder is beyond the bounds
> > > of discussion of android-developers which is supposed to be confined
> > > to the SDK APIs.
> >
> > > On Nov 4, 10:57 pm, xhy wrote:
> > > > Hi all,Now I come across a question,I want to visit the system folder
> in
> > > the
> > > > android file system.So i add the
> > > "android:SharedUserId=android.uid.system"
> > > > in the manifest.xml,But I can not visit the USB device if that.
> >
> > > > --
> > > > Hongyue Xu
> >
> > > --
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> >
> > --
> > Hongyue Xu
>
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--
Dianne Hackborn
Android framework engineer
hack...@android.com
Note: please don't send private questions to me, as I don't have time to
provide private support, and so won't reply to such e-mails. All such
questions should be posted on public forums, where I and others can see and
answer them.
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