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Archive for the ‘System Administration’ Category

OpenSSH: Using a Bastion Host

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 match the h...

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Categories: System Administration

Cache has broken packages, exiting

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: This is an older Ubuntu server running 12.04.5 ...

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Categories: System Administration

MySQL OOM'ed, But Pelican Lives

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 fac...

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Categories: System Administration

Removing a Single Line from known_hosts With sed

Ever so often, something changes on the network, and you find that your .ssh/known_hosts file has gotten out of date.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...

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Categories: System Administration

Changes to OS X TCP Performance Tuning

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parameters on one of my OS X 10.11 servers, I noticed that my existing OS X TCP Performance Tuning page had gotten out of date.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 place since that is the definitive page loca...

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Categories: System Administration