Tango Devlopment

Tag: ubuntu

Posts related to Ubuntu/Debian Linux

  • Implementing IPv6 Part 2

    We are quickly running out of IPv4 addresses. Are you ready for World IPv6 Day on June 8th, 2011? I have prepared my configuration on OpenWRT and Ubuntu. This includes configuring DNS using bind, email using Exim, and a Squid web proxy.

    Having verified that I could establish IPv6 connectivity, I chose to improve my connectivity. This started with getting a tunnel from Hurricane Electric and updating my configuration. I then updated my bind server and Exim mail server support IPv6 addresses. This posting updates and continues from my post on Implementing IPv6 6to4 on OpenWRT.   Review it for information on creating a tunnel and running radvd on OpenWRT. (more…)

  • Blocking Spam with Exim

    Recent reports indicate that spam is increasing again.  I have been using Exim to filter spam for several years.  Some recent tuning I have done have decreased the percent of spam which reaches my spam filters.   This article provides a discussion of the techniques used, and provides implementation examples.   Spambots tend to be simple programs which don’t handle slow servers very well.   Using a greylist is effective method of blocking them as they usually don’t retry.   My latest changes use delays to cause many spambots to abandon their attempt.  Greylisting is used only for poorly configured servers that make it to the Recipient command.

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  • 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. (more…)

  • 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.

    This page has been updated in 2019 to reflect changes in the tools.

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  • 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. (more…)

  • 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. (more…)

  • 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. (more…)

  • 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. (more…)

  • 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. (more…)

  • 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. (more…)