1. Postfix 2.3 and clamav-milter

    Posted on in System Administration

    Postfix LogoYou've probably been using Postfix and ClamAV for a long time. Prior to Postfix 2.3, you had to have an AMaViS daemon running to act as the glue between Postfix and ClamAV.

    As of version 2.3, Postfix now supports Sendmail 8 Milter protocol. Now you can cut AMaViS …

  2. Enabling Firefox's Session Restore

    Posted on in Software

    One of the features of Firefox 2 is Session Restore. By default, if Firefox needs to restart for an update (or crashes), it will restore your session to the state it was in at the time of restart. That means your tabs and windows will be just like you left …

  3. Server Naming Conventions

    Posted on in System Administration

    Every machine needs a name. As soon as the second server is ready to go, the name SERVER no longer seems like a great idea. When deciding how to name servers, there are two primary conventions: functional names and unique names.

    Functional Names

    Functional names take the job assigned to …

  4. UDLD In Radio-Based Metro Ethernet Rings

    Posted on in Networking

    <acronym title="UniDirectional Link Detection">UDLD</acronym> is a Cisco protocol designed to detect and disable unidirectional links in Ethernet (fiber or twisted-pair). In the case of a radio-based Metro Ethernet ring, UDLD goes the extra mile in preventing Spanning-Tree loops and user service interruption.

    4 Switches and Spanning-TreeIn this simple network of …

  5. VoIP Hairpinning Issues

    Posted on in voice

    When using Asterisk and a remote bank of <acronym title="Primary Rate Interface">PRI</acronym>s (or any other form of <acronym title="Public Switched Telephone Network">PSTN</acronym> connectivity for that matter), you may encounter an issue known as hairpinning. Hairpinning describes what happens when a call coming from …

  6. Courier authdaemond Breaks On Hidden Whitespace

    Posted on in System Administration

    A buddy of mine was recently setting up a new installation of Courier with virtual user support via MySQL. He ran into an issue when trying to get authdaemond to connect to a remote MySQL installation. No matter what he changed in authmysqlrc, the following kept appearing in his mail …

  7. Command Logging is Vital to System Administration

    Posted on in System Administration

    If you're like me, it probably seems obvious that command logging is an important part of system administration. Any change I make, whether it's on a router or server, is logged somewhere. Although folks give plenty of reasons why they don't use tools like sudo for super-user functions (inconvenience and …

  8. Using Alpha-Channel Transparency in Photoshop

    Posted on in Graphics Design

    Transparent PNGs look simple when they work. They look amateurish when they do not.

    The difference is usually not the PNG format itself. PNG supports transparency just fine. The problem is almost always the mask: hard edges, dirty pixels, color halos, or an export path that flattened the image against …

  9. Adding macOS Users Remotely from the Command Line

    Posted on in System Administration

    There was a time when adding a Mac OS X user from the command line meant talking directly to NetInfo with nicl, copying a user template with ditto, and hoping you did not fat-finger a UID. That was useful knowledge in 2007. It is also very much not how I …

  10. Implement a Sensible Naming Policy in Cisco IOS

    Posted on in Networking

    Network configuration names are not decoration. They are operational metadata. When something is broken at 2:00 a.m., the difference between ACL-EDGE-IN and access-list is not aesthetic. It is the difference between narrowing the blast radius quickly and spelunking through hundreds or thousands of lines of Cisco IOS configuration …

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