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Source nat allows you to masquerade a different external ip address based on the internal ip address. For example, you may have a few IP addresses on your ipcop and you want to use a different ip for a certain internal machine (eg a mail server), so you decide you need to use source nat (snat). Its pretty simple to set up once you know what chain to put it in on the ipcop!

To get it working without any mucking about, just log in with ssh and chuck something like this at it:

There seems to be a lot of moaning that network manager in the latest alpha of ubuntu doesnt pick up wireless networks, with the blame given to nm, kde, gnome, ubuntu and linux in general. In the case of intel wireless at least, its a simple fix - because linux-ubuntu-modules has not yet been released for 2.6.26-3, the needed iwl firmware is not there (a quick look in /var/log/syslog confirms this). There are a few ways to fix this:

This is a pretty specific recipe: Setting up an ipcop as an openvpn server, and using dd-wrt as a client in a branch office or other remote location.

If you are running linux on your xbox, you may well have the cromwell bios on your modchip, a nice quick way to determine the version of your cromwell bios is to use raincoat to read it, then grep the bios image for version strings:

(On Xebian:)

su -

apt-get install xbox-raincoat

raincoat -r /tmp/biosimage

strings /tmp/biosimage | grep -icromwell

This should give you something like:

Cromwell 2.40  

There are a couple of howtos around for getting Zimbra's antivirus tuned up a bit, but here is an Ubuntu-specific one!

Dimdim is a cool new open source meeting service that lets you share your desktop, presentations, audio and video. Its also web based, and needs no installing. On top of all this, it works on Mac, Linux and even Windows! Its still alpha at the moment, but definately useable. Heres how to install it on Ubuntu server 6.06 or {insert your distro here}. The readme that comes with the tarball is very good, so have a look at that as well, but here are the basics:

Ive been using RAID1 with mdadm for imaging servers for a while and it has been very reliable, but recently ran out of space. The 2 disks are 160Gb and I wanted to replace them with 400Gb disks, without having to muck about with copying files etc. Heres how to do it:

This is done on ubuntu dapper server, but I doubt it wil change between distros, so it will also work on {insert your distro here} with no (or very little) modification.

Swap disks

Remove one disk, replace with a bigger one.

This is a really simple one, but can cause a lot of weeping and gnashing of teeth. You were given the default "ubuntu" hostname when you installed, and now you want something cooler that enhances your street cred. Heres how to change it:

Edit /etc/hostname and change to the new value, you can use nano instead of vi, but remember that real men prefer vi.

Zimbra has some cool graphs to show to suits, but they are only updated once per day, so you can see the previous day's stats, but they are not current right now. To update the statistics graphs manually, just log in to the zimbra server with ssh and su to the zimbra user

sudo su
su - zimbra
/opt/zimbra/libexec/zmgengraphs

This will kick off the graph generation process. When its done, refresh the admin console and show off your new, up-to-date graphs.

Its really useful to have a backup mail server if you receive smtp connections directly. Postfix can do this very easily, and takes minutes to set up. You could get a vps cheaply somewhere and set it up with just postfix and save yourself a lot of trouble if your main mail server goes down.

The Zimbra web interface has a cool search folder feature, just like Thunderbird or Outlook, it allows you to specify search criteria, and then save them as a virtual email folder. Every time you go to this folder, the search you specified is performed, and the results are shown in this folder. For people with huge mailboxes, this is a really good thing!

A simple but really useful one is "unread":

IPCop is a great firewall distro that you can have up and running within minutes, but there are a few really useful bits missing. No sysadmin's day is complete without the words "why is the internet so slow" being uttered by one of the flock - now you can answer with a smile and find the bugger who is slowing it all down...

Use certificates instead of passwords for passwordless ssh logins

This is pretty old news, but SSH can use certificates instead of passwords to log you in. This can make life a lot easier, especially when you need to connect to a lot of different ssh servers. It can also improve security, as users wont be scribbling passwords down. On top of this, its pretty easy to set up as well:

So you have a DVD that you want to store as a file instead of lugging the plastic around, and wondered how to do this on your linux box. Wonder no more! Handbrake is a nifty cross-platform dvd ripper that you can use in the linux shell (this makes you look well hard). If you are soft, you can also install it on windows or OSx, but I digress. Obviously you should only do this for home DVDs that you own or have permission to duplicate, ignoring this will result in DIRE consequences. DIRE!

You have your SSL-explorer running and all your users are using their remote desktops (http://www.subvs.co.uk/ssl_vpn_on_ubuntu ), but there are a couple of neat things to do after that as well, like web forwarding, file management and port forwarding: