Category: System administration

  • Ubuntu/Debian & Postfix: Increase attachment size limit

    By default postfix limits the attachment size to about 10 MB. You can determine the current limit with the following command: # sudo postconf | grep message_size_limit message_size_limit = 10240000 To increase the limit add (or change) the following setting in the file /etc/postfix/main.cf: # 20MB message_size_limit = 20480000 After restarting the postfix service the […]

  • Apache 2: Set up Thawte SSL 123 Certificate

    Here is a short tutorial how to set up a Thawte SSL 123 SSL certificate (a domain-only validation SSL Certificate). In a nutshell, it takes two steps: First, you need to create your private key and the certificate signing request to request the certificate. In a second step you need to configure your web server […]

  • Debian Lenny 5.0: Bind RPC port mapper portmap to local loopback

    By default on Debian Lenny the portmap service listens on UDP port 111. For security reasons it could by reasonable to prevent portmap from opening the port if you do not run services like NFS or NIS services that depend on a RPC port mapper like portmap. One way to to disable the open port […]

  • Hetzner EQ root server & XenServer 5.6: Howto use additional IP subnets

    With each Hetzner EQ root server you get a limited number of four IP addresses. Since you need one IP address for your XenServer host system and one for each guest system, the number of guest system is limited by default. To overcome this limitation, you can buy additional IP subnets (/29 with 6 IP […]

  • XenServer 5.6: Kernel update for (paravirtualized) Ubuntu 10.04

    I used jansipke’s great tutorial “Installing XenServer Tools on Ubuntu 10.04” to set up a paravirtualized Ubuntu 10.04 guest system (to enable support for the XenServer Tools) on a XenServer 5.6 host system. Using this technique, it is important to update the host system after a kernel update in the guest system. In the simplest […]

  • XenServer 5.6 & Debian Lenny: Fix apt-get/aptitude GPG error

    If you follow the instructions in the Citrix Developer Network to set up a (paravirtualized) Debian Lenny guest system apt-get or aptitude will show the following error W: GPG error: http://updates.vmd.citrix.com lenny Release: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 841D6D8DFE3F8BB2 W: You may want to run apt-get […]