Thin clients freeze hard when out of RAM

Jim Kronebusch jim at
Sun Sep 2 19:31:45 BST 2007

Problem solved (or at least identified).  Firefox has a bug if you want to call it that,
that caches pixmaps to X11.  This can chew up all available RAM in a hurry and once full
completely freezes the client.  There is a hack you can put into ldm that will not allow
any application to consume 100% of RAM causing the app to crash upon request of too much
RAM, but at least keeps the client running.  But this still doesn't allow you to open
certain websites.  Upon testing of other browsers (thanks to Robert Arkiletion) I found
that if you have Firefox working the way you want, just apt-get install opera and your
good to go.  Now I know that Opera isn't exactly the preferred client and also isn't
"free" software, but if you're having trouble with Firefox crashing your clients, this
is a good workaround until a way to keep firefox from caching pixmaps is found.

Also modifying the default nbdswap size from 32MB to whatever you need to handle certain
sites (the ones some of our students ran into required a minimum of 500MB) helps.  But
this can quickly use up HD space on the server, create more network activity, and is
slower than the use of RAM.  So although this works as well it is not a perfect solution.

However if you absolutely need to use Firefox addition of the ldm hack along with the
nbdswap increase, things should be very usable although not ideal.

If anyone wants a good pet project....please find a way to disable firefox from pixmap
caching to X11.  It looks like many could benefit from this.

I will post in 2 separate posts a howto for addition of the xramperc option in ldm and
how to increase your nbdswap.


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