[Live-demo] System behaviour in low disk space conditions

Thu May 16 03:01:20 PDT 2013

Dear Jeremy,

Thank you very much for taking the time to write your feedback regarding 
OSGeoLive.
We really appreciate it. We wish we could get feedback from more users.

Some comments inline:

On 05/15/2013 06:52 PM, Jeremy Morley wrote:
> Dear all,
>
> While you're thinking about Live 7.0,some reflections from running version
> 6.0 from USBs with students this last semester. I know your main target is
> DVDs but these may be of interest.

Actually the strategy we use to build the system nowadays, includes only 
one building step (mini iso), so there are no second class citizens in 
the process, only limitations per medium (eg. space limit for 
persistence in usb sticks, or space limit to dvd image). There is no 
special attention to the DVD version, it is just more practical (and 
cheap) to distribute those to conferences and workshops.

> Firstly, it's pretty common when I'm working with students that they're
> not careful with disk space but are used to having lots of it. Even if you
> give them another partition on the USB stick, or even tell them about
> accessing the hard drive on the machine from the Live system, inevitably
> one or more will just download big ZIP files to their home directory,
> unpack the contents there, never clear it out, etc. So eventually the home
> directory & thus the system runs out of space. My observation is that the
> system degrades very poorly in these circumstances, becoming unpredictably
> unreliable and sometimes unbootable. Often it's PostgreSQL that seems to
> be the poorest to cope but this is all anecdotal and hasn't been performed
> in test conditions. Is there any way that this behaviour can be modified,
> or at least some system monitor be included to warn of the impending
> situation?  As a long-term user of computers & Linux/Unix-based systems I
> can recognise the sort of system instability that arrises from
> out-of-disk-space conditions so I know to go looking for it but the
> students don't and it causes grief!
I am sharing the same problem too, since I use the disk to teach 
classes. In my case I avoid the use of persistent usb sticks and prefer 
to use the VM version which has more space available in the virtual 
drive. Of course this is taking longer to setup, but students get to 
learn how to use virtual machines too :)

Since the mini iso is large enough not to leave much space to a 4GB usb 
stick for persistence, I am thinking that given a minimum of a 8GB usb 
stick, we could apply some quota to the default user (something around 
2-3GB?) so that the system is protected from running out of space. This 
does not solve the problem of system updates though, that can easily 
occupy much of the free space...

>
> Secondly, the university runs a proxy to the Internet. The proxy setting
> just in Xubuntu is fiddly enough (requiring updates to system files under
> sudo in a number of places) and then there's the proxy settings in the
> various packages. Even if it's not for this release, could there be a
> long-term aim to provide a means at least to set the system proxy, and
> better yet the package proxy settings? In part this is "my" problem as the
> instructor in creating a tweaked version of the Live image to install on
> our systems but actually if the students want to take the USB between the
> uni and home (and thus out from behind the proxy) it gets fiddly for them
> too. IIRC, plain Ubunutu has a settings panel that performs this task -
> I've no idea about lubuntu etc.

Hmm, this is tricky. We should check if there is a better settings tool 
to include in Xubuntu.
I don't see switching to plain Ubuntu as a possible solution.

>
> A final issue is of ways to back-up from the system. I realise that a Live
> system is not exactly intended for long-term use, and particularly not
> from a USB drive.

Indeed, it is more for testing purposes.
For long term use, we propose either installing the system or using the 
VM version.

> However I'd like to be able to use this with students
> across a period of ~15 weeks. This year I found that the batch of USB
> drives (Kingston DataTraveler 100 G2 16GB drives) did not perform well,
> and 3-4 of them have failed (at a low level in the hardware, it seems, so
> both partitions are lost & the devices are not recognised on the USB bus
> as mass storage devices (or at all)). In some cases of partial failure
> (e.g. when the booted system has filled and is not bootable) I can mount
> the drive on another Linux system, mount the squash and casper files and
> fish around to extract some of the contents, e.g. to copy to another drive
> before re-imaging with a fresh Live installation. I'd just support the
> requests to present an easy way to access the Live file system when the
> stick is plugged into another system, or at least documentation on how to
> mount the systems. I have, for example, yet to find where the PostgreSQL
> contents are when accessing from a separate system. Alternatively, advice
> on how to back-up the system would be very beneficial (maybe right up
> front on the Live GIS Disc Quick Start for USB wiki page?).

This is not specific to OSGeoLive, but affects all Ubuntu based live 
systems, since we do the spin-off the official way.
Yes, I see that a wiki page would be helpful.
>
>
> I hope this helps. I realise the third topic is rather nebulous! Should I
> enter any of the above as tickets? (They feel like higher level concerns
> to me).

Since we already have tickets that include high level concerns, 3 more 
would be welcome :)

Regards,
Angelos
>
> Regards,
> Jeremy
>
>
> -- ------------------------------------------------------------ --
> Jeremy Morley
> Geospatial Science Theme Leader, Nottingham Geospatial Institute,
> Triumph Road, University of Nottingham. NG7 2TU, United Kingdom.
> Web:http://www.nottingham.ac.uk/ngi      Twitter: jeremy_morley
> Tel.:  +44/0 115 84 68411
> Email:jeremy.morley at nottingham.ac.uk
>
>
>
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-- 
Angelos Tzotsos
Remote Sensing Laboratory
National Technical University of Athens
http://users.ntua.gr/tzotsos