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VSFTPd, SSL, and Firewalls

December 5, 2014 – 1:58 pm |

If you ever wanted to configure SSL/TLS encryption for an FTP server behind a firewall, the “Google wisdom” ranges from “a major pain” to “can’t be done”. Fortunately, things are not all that bad. In …

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Unix and Linux network configuration. Multiple network interfaces. Bridged NICs. High-availability network configurations.

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Reviews of latest Unix and Linux software. Helpful tips for application support admins. Automating application support.

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Disk partitioning, filesystems, directories, and files. Volume management, logical volumes, HA filesystems. Backups and disaster recovery.

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Distributed server monitoring. Server performance and capacity planning. Monitoring applications, network status and user activity.

Commands & Shells

Cool Unix shell commands and options. Command-line tools and application. Things every Unix sysadmin needs to know.

Security »

Late Night Rant #23: Kim The Sony-Slayer

December 17, 2014 – 10:09 pm |

Sony execs are shedding crocodile tears over the latest IT security breach that brought substantial financial losses to the company. Let’s not dwell on the trivial: who did it and why are irrelevant technicalities. How this hack was possible, on the other hand, is the question worth our attention. Read the full story »

RHEL/CentOS Yum Operations

December 14, 2014 – 11:42 pm |

The Yellowdog Updater, Modified has more features than most of us will ever need. Below are some hopefully useful examples that will help keep your system maybe secure by replacing old known bugs with new …

Using Pflogsumm Postfix Log Analyzer

December 4, 2014 – 12:29 am |

Pflogsumm is an oldie but a goodie. It’s a Perl script that sifts through your Postfix server maillog and provides you with a neat summary of events and some statistics. This information can be useful …

Visualizing Apache Logs with Logstalgia

December 4, 2014 – 12:01 am |

The Logstalgia is a cool graphical utility for visualizing the Apache access_log files. The practical value of Logstalgia is debatable, but it’s entertainment value is not in question. The managers and NOC operators can stare …

Sending Attachments Using Mailx

December 3, 2014 – 2:32 pm |

Sometimes it’s just better to attach a file to your email than to “cat” the contents into the email body. You will need the “uuencode” utility installed. On CentOS/RHEL you can install it by doing …

Fail2ban Whitelist IPs

December 2, 2014 – 9:16 pm |

Fail2ban is an excellent security tool that will do a good job safeguarding your server. However, using fail2ban you may run into two issues: friendly fire and inability to permanently ban hostile networks. I already …

Identifying Available IPs on the Network

December 2, 2014 – 2:31 pm |

At some point available IPs on your network may become few and hard to come by. Documentation becomes outdated and does not accurately reflect which IPs are still in use. A good starting point would …

Using truss and nawk to Trace Solaris Processes

November 18, 2014 – 1:54 pm |

Here’s the problem I ran into today on a Solaris 11 SPARC server: an application UI would occasionally freeze for a few second when executing a particular function. Nobody could quite figure out where the …

Adding Swap with Solaris 11 ZFS

October 22, 2014 – 4:24 pm |

With the swap partition residing on a ZFS filesystem, you have an easy way of adding swap on the fly. Reducing swap is not quite so simple, but we’l talk about that later. To check …

Enable NTP Client on Solaris 11

October 7, 2014 – 8:27 pm |

Just some quick instructions for configuring and enabling NTP client on Solaris 11.

PHP Unable to allocate memory for pool

September 9, 2014 – 10:57 pm |

The following error may be found in /var/log/httpd/${domain}/error_log when APC memory is set too low: “PHP Warning: require_once(): Unable to allocate memory for pool”. APC is Alternative PHP Cache. You can check the version of …

Getting Epoch Time on Solaris 10 and Older

September 8, 2014 – 3:57 pm |

You can get the epoch time on Solaris 11 and Linux simply by running the date command:

Installing GoAccess on CentOS/RHEL

June 24, 2014 – 11:02 am |

GoAccess is a simple but useful “top”-like CLI utility giving you a quick overview of the Apache access_log entries.

NTP Client Configuration on CentOS

May 15, 2014 – 8:31 pm |

Just some quick note on configuring NTP client on CentOS/RHEL/Fedora and forcing time update. Just got tired of having to remember these steps every time I run into NTP.

Searching Log Files

April 18, 2014 – 4:40 pm |

This is a quick example of finding the first and last occurrence of an event in the log file. This can be useful for determining the service outage window and for general troubleshooting. In the example below I am looking at the PostFix maillog file, trying to figure out the duration of the problem I’ve been having with one of the mail relay servers.

WordPress Remove Extra Line Breaks

December 2, 2013 – 3:09 pm |

Frequently, imported posts or posts created by auto-blogging plugins will create unnecessary tabs, newlines, and line breaks. This has a negative impact on readability and aesthetics of your site. If you cannot address the problem …

MySQL mysqlhotcopy Script

December 2, 2013 – 1:30 pm |

Here’s a simple script to automate mysqlhotcopy runs from cron to backup multiple MySQL databases. The script loops through the list of databases and kicks off an instance of mysqlhotcopy in the background for each one. Really, …

Monday Rant: HP’s Web Site Fail

November 18, 2013 – 8:21 pm |

Every time I come across a link leading to HP’s angry garden salad of a Web site, I feel as if I stepped in chewing gum. Unfortunately for me, being a sysadmin means I have …

Dynamic Variables in BASH

October 10, 2013 – 9:32 am |

Assigning variables is easy if you know how many you have and what they are called. The value of a variable can be, well, variable. But the names and number of variables need to be …

Free Rescue CDs for Windows

October 5, 2013 – 11:32 am |

This is just a quick summary of the more popular rescue CDs out there. All of these are Unix-based bootable ISOs. Some are available as self-burning EXE files, which may be useful if you don’t …

Linux Man Pages (man1)

October 1, 2013 – 3:03 pm |

The current version of manual pages for the most common Linux commands and options. Just for your online convenience.

My Script Won’t Run from Cron!

September 27, 2013 – 10:36 am |

This is a fairly common issue with running scripts from root cron: the script works perfectly when ran manually from command line, but fails in unexpected ways when running automatically from root cron.

Configure Anonymous FTP on Solaris 10

August 25, 2013 – 2:30 pm |

Below are basic steps for configuring anonymous FTP service on Solaris 10. Use with caution.