Tag Archives: ubuntu

Posts related to Ubuntu/Debian Linux

Transparent Squid Proxy

Over the holidays, I had a user experience and attempted browser hijacking.  It appeared to have bypassed my squid proxy.   My updated configuration now sends all web access via squid.  The old firewall rules, that allowed direct access to the Internet, have been replaced with a transparent Squid proxy.  This runs on my existing Squid Proxy using another port. Continue reading

Manual networking for KVM

I found the networking configured by libvirt (KVM) did not allow me to firewall the network as I desired.  I use Shorewall for firewalling, and DNSMasq for internal DNS and DHCP.  After a little experimentation, I found that I could configure Ubuntu to create the network.  This allows me to get a reliable firewall configuration with a virtual DMZ.

The virtual hosts are assigned to a bridge, and only have connectivity to other networks as defined in the Shorewall configuration.  A single DNSMasq server provides DSN an DHCP services for all virtual servers, as well as the network the server is connected to.  The network and firewall configuration remains consistent even as servers are cycled up and down.  An additional bridge was created to support virtual servers in the DMZ zone. Continue reading

Remote Desktops with VNC and RDP

I find it useful to have a remote desktop to my Ubuntu systems.   On secure connections I have been using VNC via xinetd.  Connections with xrdp where possible, but it wasn’t launching the desktop for the connection.  For secure terminal connections, I stick with with ssh.  All these connection have a login at the start of the connection. This is how I do it. Continue reading

Implementing DKIM with Exim

This article was updated in February 2014 to reflect changes policy and reporting options. The earlier ADSP (Author Domain Signing Practices) information has been removed.

DomainKeys Identified Mail (DKIM) provides a method to confirm the origin of an e-mail. DKIM also provides some protection against tampering. Unlike SPF, this validation applies to the contents of the message when it is signed. Like SPF, the information required for validation is added to DNS. Continue reading

Signing Return Path Addresses with Exim

I have been receiving a fair amount of Spam from an e-mail forwarder.  They are unwilling to correct their problems.  Much of the Spam they forward is the form of bounce notifications.  Attempting to reject other Spam resulted in more notifications.  To control this Spam I implemented signed return path addresses.  As a side benefit, I am also rejecting bogus notifications sent directly to me.

Signing my return path allows me to reject faked notification e-mail.  The SMTP standard requires that no email sent with a null return path “<>” (aka Envelope Sender) be returned.  Its purpose is for allow for notifications about existing messages.  These includes notifications such as address unknown, message delivered, and message read.  E-mail notification which are not about a previously sent message can be refused . Signing the return path allowed me to reject such invalid notifications. Continue reading

Cfengine 2 for Debian and Ubuntu

Cfengine is a declarative system configuration tool.  This helps apply standards to system configuration. The configuration files specify the desired configuration and the engine applies these specifications to the system.  It is useful to:

  • Distribute configuration files;
  • Install standard packages (including on Debian and Ubuntu with code provided here);
  • Cleanup old files; and
  • Ensure certain programs are/are not running.

This documentation applies to Cfengine version 2. . The latest version has made significant changes to the scripting structure, but maintains the capability to run the version 2 format files. Continue reading

Setting up Squid Proxy on Ubuntu

Squid is a proxy service for HTTP and other requests.  This article covers installing it and configuring it to run on Ubuntu as a transparent proxy.  This documentation includes configuring Web Proxy Auto-Discovery (WPAD) via DHCP and DNS.

I run a heterogeneous configuration.  This provided a number of challenges as various implementations of WPAD were encountered.  These each seem to require something different.  The final configuration works for Ubuntu, Windows X/P, and Windows Vista.  Both Internet Explorer and Firefox configured correctly. Continue reading

Connecting a Palm via USB

The computer to which I had been synchronizing my Palm Tungsten E died a while ago. I explored the two options for connecting to my Ubuntu system using a USB cable. The fastest is to use a direct USB connection. However, I wanted to ensure I could synchronize over a network connection. I also configured and tested setting up a PPP connection over USB. Continue reading

Monitoring with Munin

Munin is a system monitoring program designed to capture and graph performance statistics with minimal configuration. It is significantly easier to configure than MRTG and has a wide variety of plugins.  The Ubuntu (Debian) installer will setup a reasonable configuration on installation.  It requires one server, and a client daemon on all monitored servers including the server. Scalability to large (campus) environments has been reported to be an issue Continue reading

Installing WordPress on Ubuntu

WordPress is available as a packaged application for Ubuntu.  However it requires a bit of post installation configuration. The installation will install the apache2 multi-user server if no server is installed. I modified the installation to run over top of an existing site.  The default installation creates directories under /var/www, which I move to /srv. Continue reading