tOMPSON’s blog

Today I updated my vmware test environment by downloading a new Ubuntu 8.10 server appliance. After extracting the zip file and staring the server inside my vmware player version 2.5.1 there was no eth0 device available. I tried to start it manually with ifup but that did not work.

A quick google research brought up Eric Martin’s excellent post about how he fixed that problem. It seems that my vmware player instance created a new MAC address for the network adapter. I deleted the old entry for eth0 from the /etc/udev/rules.d/70-persistent-net.rules file and changed eth1 to eth0 in the second entry. After a reboot everything worked fine again.

Yesterday I installed a vnc server on my Ubuntu 8.04 LTS server. I did this because I want to run some GUI applications like a BitTorrent client on it. The last time I installed a vnc server on a machine without a window manager was back when I was using Redhat. So I did a little search and found out that the best way is to install gnome-core and tightvncserver by issuing

apt-get install gnome-core tightvncserver

After the first start of tightvncserver I was able to connect to port 5901. Tightvnc only starts a simple window manager and an xterm. To get tightvnc start a gnome session I had to edit the file xstartup in the .vnc folder of my home directory. I removed the line

x-window-manager &

at the end of the file and added

gnome-session &

After stopping the vnc server with the following command line

tightvncserver -kill :1

and starting it again I was entering my gnome session when connecting with my vnc viewer (UltraVNC).

Lately I had troubles with my Debian Etch installation running in a VMWare server on a Windows 2003 SBS. I had to reboot the guest system multiple times until the eth0 network interface could establish a connection. It seems that this hat something to do with the system choosing the wrong of to network modules.

On startup the pcnet32 and the vmxnet modules where loaded (which I could see in /var/log/messages and with lsmod). I tried to change /etc/modules.conf by adding alias eth0 vmxnet or alias eth0 pcnet32 but that did not help.

Based on these two sites I tried to add EthernetX.virtualDev = vmxnet (I set X to 0 for the first and only network interface) in the .vmx file of the virtual machine and then to add the alias eth0 vmxnet in /etc/modules.conf - and that did the trick.

There are a lot of sites around the web that inform us about the “OpenSSL debacle” in the Debian based Linux systems. A piece of code that was committed “accidentally” about two years ago limited the amount of possible SSH keys to about 32000. This means brute force hacking attempts based on the list of possible keys could easily lead to success.

When I read this about a week ago I reacted immediately and updated my system with:

aptitude update
aptitude dis-upgrade

The OpenSSL wiki page describes what has to be done for the various installed packages that use OpenSSL certificates. The tool dowkd.pl allows you to check if there are vulnerable keys on your system.

I use PuTTY a lot in combination with keys created by PuTTYgen - these keys stored on my various systems are of course not affected by this problem.

As I wrote in my post about my mail server configuration I am using postfix as MTA for my emails. This week a friend had problems to send me an email containing some attachments. He got the following error message from my server:

SMTP error from remote mail server after MAIL FROM:<anyone@anywhere.com>
SIZE=16282613:
host example.net [87.230.24.156]: 552 5.3.4 Message size exceeds fixed limit

I was a bit confused because I did not set any limit. After checking the postfix manual and running the following commands

postconf -d (showing the default settings)
postconf -n (showing explicitly configured settings)

I found out that the default maximum message size is configured like

message_size_limit = 10240000

which means about 10MB. I ran the following commands to adjust the limit:

postconf -e "message_size_limit = 102400000"

Now I am able to receive mails with a maximum size of about 100 megs. Additionally I change the maximum mailbox size with the following command:

postconf -e "mailbox_size_limit = 512000000"
postconf -e "virtual_mailbox_limit = 512000000"

Some months ago I wrote this post about Setting up subversion on Debian etch. I mentioned that you could use the AuthzSVNAccessFile directive to add more detailed access control for your subversion repositories. That time I did not need it and I did not look into the detailed documentation. Today I needed to setup another repository for a new user group so I wanted to define which users has access to which repository.

The whole process was simpler than I thought it would be. I just had to add the following line to my Location in the apache virtual host that points to my repository:

AuthzSVNAccessFile /path/to/access/file

Then I created the file I pointed out with the directive. There I added entries like

[main:/]
tom = rw

[other:/]
tom = rw
frank = rw

With this entries I defined which users have access to the two repositories main and other. It is as easy as this. The modules configured per default for svn in Debian etch already have loaded the authz_svn module. For more details see the svn documentation.

Today I had a problem with my Ubuntu system running in a VMware Workstation on my notebook. First I noticed that every key I pressed occurred multiple times. Then the screensaver appeared very often after a short period of time. I looked for the reason and found out that the clock of the guest system ran way to fast.

A quick web search told me that I am not the only one with this problem. I found this article in the VMware knowledge base. After following the directives in the solution part everything worked fine again. I had to reboot because I could not find the VMware Registration Service in my services.

It seems that this problem occurs on notebooks because of their power saving mechanisms. VMware is not able to find out the correct CPU clock speed for the virtual CPU because the host is constantly changing the CPU frequency.

UPDATE: Today I found out that I still had problems with the changing CPU clock speeds. I downloaded the RMClock Utility to observe the CPU clock frequency on my host system. By selecting another power scheme in the Windows XP control panel I was able to control that.

I am running my own mail server now for over five years. There are a lot of good free email services out there but I am not satisfied with their spam filters. I am getting about 300 spam mails a day and with my current solution only one of them makes it into my inbox per month.

The second reason is that I do not want to delete or archive my mails to often and I want to have access to them anywhere at any time. Therefor I need an IMAP server with a lot of storage. Most free mail services provide this nowadays but did not five years ago. I thought about using GMAIL lately but I am not completely happy with storing all my mails on Google servers.

First I used an old PC that ran in my home office day and night. My home internet connection always had a high enough upload bandwidth to allow that. The mail server was no dedicated mail server for my domain. I used fetchmail to receive my emails from multiple POP3 servers.

About six months ago I configured a VPS machine to act as the dedicated mail server for my domains. I host multiple mail accounts for my family and friends on it. This post explains what I did to configure my perfect personal mail server.
Read the rest of this entry »

Aaron just posted a short teaser video for a vim screencast tutorial he is producing. It show only some of the features vi improved offers:

This one I found on Lifehacker: They provide a one page linux manual with the most important Linux commands (in fact it is two pages long but if you print it double sided

Although it is 8 years old most of the information is still very useful.