Martin's Technique Blog

Replace Firefox 3 by Firefox 2 in Ubuntu 8.04 Hardy Heron

Martin Wunderli — Sat, 31 May 2008 07:49:00 GMT

Hi,

Firefox 3 in Ubuntu Heron gave me quite some trouble, especially with our SSL-VPN and Tab Mix Plus Add-On: Both do not work. So I decied to go back to Firefox 2. Here is how I did it:

Completely remove Firefox

sudo apt-get remove --purge firefox firefox-3.0 firefox-3.0-gnome-support firefox-gnome-support

Install Firefox 2

sudo apt-get install firefox-2

Create link to make all programs happy which call firefox

sudo ln -s /usr/bin/firefox-2 /usr/bin/firefox

As you can see, I more like to do it on the command line than in the GUI...

Cheers

Martin

Oracle Critical Patch Update October 2007 on RAC

Martin Wunderli — Wed, 31 Oct 2007 09:41:00 GMT

Hi,

Since all molecules of the CPU October 2007 are marked as 'online applicable' to RAC
(nice wording, it means a rolling upgrade is possible, not that all instances stay
online during the patch...), I decided to test it. Clusterware did not have to be
patched, by the way.

Rolling upgrade worked, so far so good. During the whole process, users could work.
However, two big issues - which are not related to this specific CPU, but to the way
Oracle describes the patch process in case of RAC - came up.

First, shutdown transactional local does not wait for a transaction to commit or
rollback if the corresponding session was established via Oracle Net and a srvctl generated service name.
Quite common, not to say standard, in a RAC environment. Some tests revealed that in
case of local connects or Oracle Net connects via SID, the shutdown waited as it
should. The solution was to shutdown the listener of the instance to be patched, to issue

alter system disconnect session 'SID,SERIAL#' post_transaction;

for all sessions, wait until they failover and then issue shutdown. Not very
comfortable but it works.

The second issue was on the VIP. Oracle recommends to issue

srvctl stop nodeapps -n NODE_TO_BE_PATCHED

This, however, also stops the VIP and does NOT failover it to another node. Which
results in TCP timeouts for new connects and failovers (sessions seem to hang). The
solution here is to explicitly start the VIP on a fully available node, e.g. with

crs_start ora.NODE_TO_BE_PATCHED.vip -c FULLY_AVAILABLE_NODE

Remote access with GUI

Martin Wunderli — Sat, 08 Sep 2007 07:15:00 GMT

For quite a while I have been an enthusiastic fan of VNC (better: tightvnc) when it comes to access a remote server including graphics. However, since the VNC variant used in my Laptop OS Ubuntu Dapper (and therefore the OS of the PCs of my wife, father, mother... :-) ) is quite slow, I was looking for alternatives.

I found one with the NX products from http://www.nomachine.com which allow me not to just start a graphical session on a remote machine (via a possibly slow line), but also attach to an existing session on the remote machine (even the graphical root window) or disconnect/reconnect to a session. There are free variants for Linux and Solaris available, unfortunately not for Windows, but VNC server or rdesktop (RDP) are ok in that case.

The most amazing experience for me was the installation. Klick on the download button and let your package manager (the debian one in my case) do the rest. Since the complete login and traffic works through ssh, no extra tunnel in a firewall etc. must be opened. An existing ssh based access infrastructure can be used.

There is also a fully GPL-ed variant called FreeNX which lacks some features like reconnecting etc.