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Pollution and Servers

There is a lot of interest in making organisations “green” nowadays. One issue is how to make the IT industry green. People are talking about buying “offsets” for CO2 production, but the concern is that some of the offset schemes are fraudulent. Of course the best thing to do is to minimise the use of […]

Mobile SSH Client

There has been a lot of fuss recently about the release of the iPhone [1] in Australia. But I have not been impressed.

I read an interesting post Why I don’t want an iPhone [2] which summarises some of the issues of it not being an open platform (and not having SSH client support). Given […]

The New DNS Mess

The Age has an interesting article about proposed DNS changes [1].

Apparently ICANN is going to sell top level DNS names and a prediction has been made that they will cost more than $100,000 each. A suggestion for a potential use of this would be to have cities as top level names (a .paris TLD […]

Solving Rubik’s Cube and IO Bandwidth

Solving Rubiks Cube by treating disk as RAM: Gene Cooperman gave an interesting talk at Google about how he proved that Rubik’s Cube can be solved in 26 moves and how treating disk as RAM was essential for this. The Google talk is on Youtube [1]. I recommend that you read the ACM paper he […]

Letter Frequency in Account Names

It’s a common practice when hosting email or web space for large numbers of users to group the accounts by the first letter. This is due to performance problems on some filesystems with large directories and due to the fact that often a 16bit signed integer is used for the hard link count so that […]

BIND Stats

In Debian the BIND server will by default append statistics to the file /var/cache/bind/named.stats when the command rndc stats (which seems to be undocumented) is run. The default for RHEL4 seems to be /var/named/chroot/var/named/data/named_stats.txt.

The output will include the time-stamp of the log in the number of seconds since 1970-01-01 00:00:00 UTC (see my previous […]

Moving a Mail Server

Nowadays it seems that most serious mail servers (IE mail servers suitable for running an ISP) use one file per message. In the old days (before about 1996) almost all Internet email was stored in Mbox format [1]. In Mbox you have a large number of messages in a single file, most users would have […]

Mobile Facebook

A few of my clients have asked me to configure their routers to block access to Facebook and Myspace. Apparently some employees spend inappropriate amounts of time using those services while at work. Using iptables to block port 80 and configuring Squid to reject access to those sites is easy to do.

So I was […]

ARP

In the IP protocol stack the lowest level protocol is ARP (the Address Resolution Protocol). ARP is used to request the Ethernet hardware (MAC) address of the host which owns a particular IP address.

# arping 192.168.0.43 ARPING 192.168.0.43 60 bytes from 00:60:b0:3c:62:6b (192.168.0.43): index=0 time=339.031 usec 60 bytes from 00:60:b0:3c:62:6b (192.168.0.43): index=1 time=12.967 msec […]

Ethernet Bonding and a Xen Bridge

After getting Ethernet Bonding working (see my previous post) I tried to get it going with a bridge for Xen.

I used the following in /etc/network/interfaces to configure the bond0 device and to make the Xen bridge device xenbr0 use the bond device:

iface bond0 inet manual pre-up modprobe bond0 pre-up ifconfig bond0 up hwaddress […]