Articles in the System Administration category

1. OpenSSH: Using a Bastion Host

   Posted on March 26, 2016 in System Administration

   Quick and dirty OpenSSH configlet here. If you have a set of hosts or devices that require you to first jump through a bastion host, the following will allow you to run a single ssh command:

   Host *
       ProxyCommand ssh -A <bastion_host> nc %h %p
   

   Change the Host * line to best …

2. Cache has broken packages, exiting

   Posted on February 23, 2016 in System Administration

   I've been getting the following error from cron.daily in my inbox lately:

   /etc/cron.daily/apt:
   Cache has broken packages, exiting
   

   That's an annoying email to get everyday. I decided I would apt-get clean and that would probably fix the problem:

   $ sudo apt-get clean
   $ sudo apt-get dist-upgrade
   Reading package …

3. MySQL OOM'ed, But Pelican Lives

   Posted on February 15, 2016 in System Administration

   I use Pingdom's free service to monitor slaptijack.com. Apparently, late Friday night, oom-killer decided that the server needed more memory and took out the MySQL server. To make matters worse, I missed the alarm from Pingdom, and slaptijack.com was down for pretty much all of Saturday. The fact …

4. Removing a Single Line from known_hosts With sed

   Posted on February 08, 2016 in System Administration

   Ever so often, something changes on the network, and you find that your .ssh/known_hosts file has gotten out of date. Usually this happens after an upgrade or device change. You'll get the rather ominous warning that REMOTE HOST IDENTIFICATION HAS CHANGED!

   If you are confident that someone isn't doing …

5. Changes to OS X TCP Performance Tuning

   Posted on February 01, 2016 in System Administration

   While updating the TCP tuning parameters on one of my OS X 10.11 servers, I noticed that my existing OS X TCP Performance Tuning page had gotten out of date. The page was nearly eight years old, so it is no surprise that happened. I updated the page in …

6. Using Redis for PHP Session Storage

   Posted on January 26, 2016 in System Administration

   I have written previously regarding using Redis for Magento session storage. You can get the same benefits of using Redis for session storage (reduced disk I/O, automatic key eviction) for any PHP application by making a quick change to a couple of settings in your php.ini. I assume …

7. Bypass RBL Check in Exim

   Posted on January 19, 2016 in System Administration

   Although I do not use Exim myself, I have clients that do. Recently, we noticed that it was taking more than 20 seconds for their SMTP banner to display when initiating checks from the monitoring server. Connecting to the server locally (on any interface IP address) did not suffer the …

8. Enable gzip in Nginx

   Posted on January 11, 2016 in System Administration

   If you have ever used any tool to optimize a web page, you know that compressing the return traffic to the client is a big win. In nginx, this is done with the gzip module. The easiest thing to do is add gzip on; to the http stanza in your …

9. Magento Home Page Returns 404 Status Code

   Posted on December 28, 2015 in System Administration

   Naturally, I ran into this problem in the middle of the night when the client was asleep and I had no access to the Magento administrative interface. The short story is that after running a re-index of the site, the home page began returning a 404 error status. A bit …

10. [MacPorts] upgrade gnutls failed

    Posted on December 07, 2015 in System Administration

    

    I ran into this issue while trying to install wine-devel on my Mid 2012 MacBook Pro running El Capitan and MacPorts 2.3.4. As the install progressed, here is the error I got:

    Error: org.macports.build for port glib2 returned: command execution failed
    Please see the log file …