Dear Network Administrators,

This CPTTM NetAdmin newsletter is to bring useful news to you, network administrators in Macau, for references without obligations, so that you can do your jobs easier and better! Hope you like it. if you'd like to unsubscribe or recommend your friends to subscribe, just email me at kent@cpttm.org.mo. Old issues are available here.

Topics in this issue:

• Automatic desktop PC provisioning
  
• Ethernet flow control is dangerous
• Four mistakes that kill VM performance
• How to provide wireless access to an outdoor area?
• Upcoming courses for network administrators

Automatic desktop PC provisioning

At Cyber-Lab the computers in the classrooms need to be cleaned and set up from scratch, possibly because a user has been infected by a virus, the OS has corrupt itself, or the hard disk has been replaced by a new one. To do it quickly, we have almost automated this entire process: Just plug-in a CD and boot the computer from it. Then it will clone a master image from a server automatically. This saves our technicians a lot of time.

How does it work? The CD is a customized System Rescue CD. On boot, it will run a small Linux kernel and then retrieve a shell script from a specified web server and then execute it locally. That script (written by us) will restore the MBR and the partition table (both hosted on a file server). It will also run ntfsclone to restore the file system from the master image (also on that file server). Below is an example of such a script:

mkdir /mnt/smb
mount -t cifs //172.18.17.1/cloning/vista /mnt/smb -o username=cloning,password=xxx
dd of=/dev/sda if=/mnt/smb/sda.mbr
sfdisk -f /dev/sda < /mnt/smb/sda.sf
mknod /dev/sda1 b 8 1
gunzip < /mnt/smb/sda1.pimg.gz | ntfsclone -r -O /dev/sda1 -
umount /mnt/smb

As you can see, it is very simple but it will save you a lot of time! This sets up the OS. For the applications, as mentioned before, we use wpkg to install the applications automatically.

Ethernet flow control is dangerous

Four mistakes that kill VM performance

Check out this article to improve the performance of your VMs by correcting four commonly seen mistakes. I am quite sure you have made one of those mistakes :-) BTW, what it refers to as "Remote Systems Administration Toolkit" is in fact the Remote Server Administration Tools.

How to provide wireless access to an outdoor area?

If you're working in a hotel, how to provide wireless access to guests by the swimming pool or on a golf course? Obviously you can't pull cables into such areas (or, you can, but the cost will be huge). A solution is to use wireless mesh AP's. They are just like regular AP's except that they don't need to connect to a wired LAN. Instead, they will act like bridges to forward frames from one to the other. Here is a case study on how the five-star Hempel Hotel in London did that. Many wireless vendors such as Cisco and Aruba have been shipping such AP's for years. In fact, Aruba enterprise AP's can be upgraded to support mesh functionality with a software upgrade.

Upcoming courses for network administrators