Monthly Archives: June 2010

SSH proxies and tunnels

SSH is a fantastic tool. Imagine you have a server at work (server.mywork.com) that you can SSH into, but you have no other access to your company network. Try the following SSH tricks:

ssh -D 9999 me@server.mywork.com

Opens a SOCKS proxy. If you tell your browser to use localhost:9999 as SOCKS proxy, you can now browse your companies internal web pages.

ssh -L 2222:internalserver.intranet:22 me@server.mywork.com

Now you can do ssh to localhost, port 2222, and that will log you on to internalserver, even if internalserver is only accessible from server, not from where your computer is now. Port 2222 on home computer is forwarded to port 22 on internalserver. This works with any other port/protocol (IMAP, OpenVPN, HTTP).

Now imagine you cant SSH to any computer at your work, but you can do SSH out of work, to your home computer. Then you can try (at work):

ssh -R 2222:localhost:22 me@myhome.com

Now, if you ssh to myhome.com:2222, it will take you to your computer at work. Port 2222 on myhome.com is forwarded to port 22 on work computer.

Finally, to keep that last connection up, there is a clever program named autossh, which automatically reconnects if needed.

Dont break any company policies!

ATA-6 drive in Titanium Powerbook

I successfully installed a WD 320Gb IDE 2.5″ Scorpio Blue in my Apple Powerbook 867MHz. Why is that interesting? Well, it is very hard to find the information that Titaniumbooks supports hard drives bigger than 127Gb. It seems ATA-5 has a 127Gb limit, while ATA-6 does not. And Apple documentation about the 867MHz Titaniumbook indicates it has an ATA-5 controller. My guess: dont expect this to work on a Titaniumbook with VGA port.

Tomato Firmware on Asus WL-500g Premium V2

For a while I have been running Tomato Firmware on my LinkSys WRT54GL. I needed to get another Tomato router for a friend, but the store was out of the WRT54GL. I ended up buying an Asus WL-500g Premium V2 instead. It took a while to install Tomato on it. Two things:

  1. Use the ND-version of Tomato
  2. Flash using the ASUS restore program (from Windows)

This worked with Tomato 1.27 ND.

I would recommend this router to anyone who considers getting a WRT54GL; it is faster, has more RAM and ROM, looks better and ASUS has some kind of flash restoration system, so you should be able to fix it even if you bricked it.

Disable Paging in Mac OS X

Virtual memory, Paging or Swap used to be a way to pretend your computer had more memory than it actually had. It made it possible to run programs that would otherwise not run at all. But it was never fast. Nowadays when modern computers have at least 2Gb of RAM, swap is not very needed. In fact you rather want your OS to use memory to cache the contents of your hard drive, not the other way around. Linux handles this thing beautifully; give it swap it does not need and it will not touch it; give it more memory than needed and it will make use of it. Mac OS X however, does not use its swap (or paging) very nicely. I found a hack that disables paging entirely in Mac OS X. I like it. Try it if you have more memory than you need. Dont use all your memory 😉

#OFF
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.dynamic_pager.plist

#ON
sudo launchctl load -wF /System/Library/LaunchDaemons/com.apple.dynamic_pager.plist

Works on 10.5, and probably more versions. You find your swap files in

/private/var/vm

and you can delete them after turning paging off.

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Welcome to this site. Here I will collect solutions, findings and facts about problems that I solve. The topic will be mostly Computers and IT.