I think it would be nice to be able to update nessus without installing it to the hard drive.
I found this and it would be nice to have a script to at automate this.
Code:
Nessus allows for a detailed (and noisy) look at a given network or a given host. It probes each subnet, domain, and host that it finds in the ways that you direct it to.

To make Nessus as useful as possible, new plug-ins for Nessus are published frequently. You can get these plug-ins for your Nessus server by running the script nessus-update-plugins. While this script eliminates the time-consuming work of downloading plug-ins, it isn't without risk. The plug-ins are not signed, and it is possible for an attacker to hijack your updates and replace them with their own malware, so don't run this on an insecure network (such as HOPE or Defcon). This is a known risk; the manpage has more information on this subject.

To run the update script, you need root privileges, so click K MenuKNOPPIXRoot Shell. The default /etc/nessus configuration directory and the /usr/lib/nessus/plugins directory are on read-only media, so you must move it out of the way, and copy it back to the ramdisk so you can download the new plug-ins to it:

root@ttyp0[knoppix]# mv /etc/nessus /etc/nessus.bak

root@ttyp0[knoppix]# mkdir /etc/nessus

root@ttyp0[knoppix]# cp -a /etc/nessus.bak/* /etc/nessus/

root@ttyp0[knoppix]# cp -a /usr/lib/nessus/plugins /etc/nessus/


Now edit /etc/nessus/nessusd.conf and change:

plugins_folder = /usr/lib/nessus/plugins


to:

plugins_folder = /etc/nessus/plugins


Now run the nessus-update-plugins script and download all of the new plug-ins:

root@ttyp0[knoppix]# nessus-update-plugins -v

. . .

./osticket_view_attachments.nasl

./freebsd_php_438.nasl

./php_strip_tags_memory_limit_vuln.nasl

root@ttyp0[knoppix]#


With all of the latest plug-ins ready to use, click K MenuSystemSecurityNessus Security Tool to launch the Nessus client.

BTW i am having problems with this part
Now edit /etc/nessus/nessusd.conf and change:

plugins_folder = /usr/lib/nessus/plugins


to:

plugins_folder = /etc/nessus/plugins
I guess I need to edit it in the root shell but I don't know how to get to the file and how to edit the file in the root shell

Tell me what you think