AlexCline.net

“Message: dualvar is only available with the XS version of Scalar::Util” Error in CentOS 5

Alex — Thu, 02 Feb 2012 19:13:32 +0000

After upgrading the CentOS 5 system that is running my company’s internal ticketing system (OTRS), the automated cron jobs for processing tickets started throwing the following error:

Message: dualvar is only available with the XS version of Scalar::Util at /usr/lib/perl5/vendor_perl/5.8.8/IO/Socket/SSL.pm line 19

This error was caused by an upgrade to the Compress::Zlib package. The newer version of the package isn’t compiled with XS support. I found some information about this error from this OTRS mailing list post from 2010 regarding RHEL. Looks like it takes about a year for RHEL packages to make it downstream to CentOS.

To fix the error, I ran the following from the command line:

perl -MCPAN -e "CPAN::Shell->force(qw(install Scalar::Util));"

After letting the cronjobs rerun, the error was gone and tickets successfully processed again.

Sending HTML Email from the Linux Command Line

Alex — Thu, 12 Jan 2012 17:27:49 +0000

Just a little tip that I found useful for a project I was working on today. I had to send the results of a MySQL query via email. Since the results are printed in a table, the formatting in the email had to use a monospace font. The easiest way to use a monospace font in an email is to enable HTML and wrap everything in a

 tag.
#!/bin/bash
mailto=email@awesome.tld
subject="The awesome subject line of your email message"
(
  echo "Subject: $subject"
  echo "MIME-Version: 1.0"
  echo "Content-Type: text/html"
  echo "Content-Disposition: inline"
  echo ""
  mysql db -uawesome -pawesomer --table < some-sql-to-run.sql
  echo ""
) | /usr/sbin/sendmail $mailto

The output looks like this:
To: email@email.tld
From: system@awesome.tld
Subject: The awesome subject line of your email message
+----------+----------+----------+
| Column 1 | Column 2 | Column 3 |
+----------+----------+----------+
| Apples   |        2 |    14.00 |
| Oranges  |        2 |   0.5000 |
+----------+----------+----------+

Stop PIPA/SOPA!

Alex — Thu, 05 Jan 2012 20:51:45 +0000

Happy New Year everyone!

I just got notifications that all my domains were successfully transferred to my new registrar. I’m now using DynaDot which is a vocal opponent of SOPA. The reason I transferred was partially to promote anti-SOPA messages and also for privacy reasons. Hopefully I’ll be much happier with my new service.

Check out the video below for information about PIPA/SOPA and why you should join the fight to oppose these proposed laws.

Reconfiguring Network Interfaces in CentOS/RHEL Systems Cloned with vCenter

Alex — Tue, 15 Nov 2011 17:28:43 +0000

While cloning CentOS VMs in our environment, I ran into a problem where eth0 wouldn’t start up. When trying to start the networking service, the following error popped up:

Bringing up interface eth0: Device eth0 does not seem to be preset, delaying initialization.      [FAILED]

The reason this error occurs is because networking adapters in cloned VMs are assigned unique MAC addresses, so they don’t conflict with the parent VM. During OS installation, the installer detects the network adapter and udev configures the mapping between the device eth0 and the MAC address. When the MAC address changes udev thinks the device is missing.

To fix this, we need to update udev’s mapping rules to point the eth0 definition to the device with the correct MAC address. Open the file /etc/udev/rules.d/70-persistent-net.rules. You should see something similar to what is below:

# This file was automatically generated by the /lib/udev/write_net_rules
# program, run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and change only the value of the NAME= key.

# PCI device 0x8086:0x100f (e1000) (custom name provided by external tool)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:50:56:9c:00:16", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

# PCI device 0x8086:0x100f (e1000) (custom name provided by external tool)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:50:56:9c:00:18", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1"

As you can see there are two PCI ethernet adapters present. The original one from the parent VM (MAC: 9c:00:16) and the new one from the current VM (MAC: 9c:00:18). To fix the issue you need to change the eth0 device definition to have the correct MAC address (9c:00:18) and remove the eth1 device. Your resulting file will look like so:

# This file was automatically generated by the /lib/udev/write_net_rules
# program, run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and change only the value of the NAME= key.

# PCI device 0x8086:0x100f (e1000) (custom name provided by external tool)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:50:56:9c:00:18", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

You’ll also want to update the /etc/sysconfig/network-scripts/ifcfg-eth0 file to reflect the correct MAC address. Then, after a quick system restart your eth0 adapter will be back up.

MySQL “duplicate entry for ’127′ for key 1″ in Rails

Alex — Tue, 01 Nov 2011 16:06:49 +0000

After building a lightly used rails application for internal use at the company I work for, I got a notification that there was an error in the application. Someone was trying to add a new record and it was failing (500 ISE). I checked the logs and found the following:

ActiveRecord::RecordNotUnique (Mysql2::Error: Duplicate entry '127' for key 1: INSERT INTO...

It turns out that this problem is triggered when the id column is of type TINYINT which has a maximum signed value of 127. This of course causes the above error to occur when record 128 is entered.

I was able to resolve this by changing the column type to INT using the MySQL client.

ALTER TABLE employees MODIFY id INTEGER NOT NULL AUTO_INCREMENT;

Disable nouveau drivers in Fedora 15

Alex — Wed, 12 Oct 2011 14:03:42 +0000

Edit: This also works in Fedora 16. During the upgrade I had to boot into single user mode to switch to run level 3 and reinstall the latest nVidia drivers. Then switch back to run level 5 and reboot.

When trying to install the latest nVidia drivers on my Fedora 15 workstation, I kept getting errors about the default nouveau video driver being loaded into the kernel. The nVidia installer creates a modprobe config file that is supposed to prevent that module from being loaded but it doesn’t work fully.

To really disable the nouveau driver, you need to edit the grub config file and add the following to the end of the kernel init line:

rdblacklist=nouveau nouveau.modeset=0

For example, your resulting grub.conf file will look like this:

title Fedora (2.6.40.6-0.fc15.x86_64)
        root (hd0,1)
        kernel /vmlinuz-2.6.40.6-0.fc15.x86_64 ro root=/dev/mapper/vg_cline-lv_root noiswmd LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb vga=794 quiet rdblacklist=nouveau nouveau.modeset=0
        initrd /initramfs-2.6.40.6-0.fc15.x86_64.img

1955 – 2011 Steve Jobs Dies at 56

Alex — Thu, 06 Oct 2011 03:42:06 +0000

“Remembering that I’ll be dead soon is the most important tool I’ve ever encountered to help me make the big choices in life. Because almost everything — all external expectations, all pride, all fear of embarrassment or failure – these things just fall away in the face of death, leaving only what is truly important. Remembering that you are going to die is the best way I know to avoid the trap of thinking you have something to lose. You are already naked. There is no reason not to follow your heart. … Stay hungry. Stay foolish.”

– Steve Jobs, June, 2005

So long Steve, you’ve been one of the worlds greatest innovators and influential beyond our time. You will be missed.

Violent Revenge Thrillers Worth Watching

Alex — Thu, 08 Sep 2011 00:57:03 +0000

I’ve always enjoyed a good revenge thriller — you know, the movies about the cold hearted, introverted protagonist whose heart is won over by a small child or a beautiful woman, only to have them stolen away or killed. The protagonist is then sent on a violent rampage killing or injuring anyone tangentially involved. In the end, justice is served for those who deserve it and lots of blood has been spilled.

Below is a list of some of my favorite revenge thrillers in no particular order.

The Man From Nowhere

A quiet pawnshop owner leads a sad and quiet life after the loss of his wife. A young girl who lives next door befriends him and brings a small ray of light into his life. When the girl’s mother steals from a powerful gang, both the girl and her mother are kidnapped. After finding the mother murdered, the man vows to save the girl with ruthless and bloody vengeance.
Man on Fire

A former special ops assassin is thrown into the world of private security when he agrees to protect a wealthy family in Mexico City. The young daughter, Pita, slowly wins over the introverted and sour on the world Creasy before she’s violently snatched under his watch. Driven and out for blood, Creasy stops and nothing to save her and make those who kidnapped her pay with their lives.
Taken

A naive teenager goes on a European getaway with her best friend. Shortly after landing, the two are snatched from the apartment where they’re staying. Listening in on the kidnapping is her father, a former spy, vows to use all of his talents and skills to save his daughter. Stolen away by human traffickers, the girl’s life hangs in the balance while her father races against the clock trying to find her before she disappears.
The Crow

One year after he and his fiancee are brutally murdered by a ruthless gang, rock guitarist Eric Draven returns from the dead to exact his revenge. Made immortal for one night by a ethereal crow, Eric must seek justice before the end of Devil’s Night.
Hanna

Hanna, a 16 year old girl, is chased across Europe by ruthless assassins. Having been trained by her father, and ex-CIA agent, to be the perfect killer, Hanna starts longing for a more normal life. Investigating her past and being pursued by a secret organization she begins to put together the pieces of her violent childhood.
Léon: The Professional

Leon, a professional hitman, is neighbor to a young girl whose family is brutally murdered by a corrupt cop. Agreeing to teach Mathilda how to be a ‘cleaner’ so that she may exact revenge for her family, Leon comes out of his dark and foreboding shell. The two begin a friendship that both benefit from and which fuels their desires for revenge.
Oldboy

After being drugged, imprisoned and tortured for 15 years, Oldboy is released without explanation. With his new found freedom, he must find his captors and exact his revenge before time runs out. While on the hunt, he learns the astonishing truth about why he was locked up.
The Horseman

After learning of the suspicious circumstances surrounding his daughter’s death, a vengeful father sets out on a road trip across Queensland to seek his bloody revenge. While in pursuit of his daughter’s killers, he meets Alice, a wayward teen who connects with the man in his moment of rage and sorrow.
Mad Max

Set in a post-apocalyptic future, Max, a quietly retired motorcycle cop is forced back into action after his family is brutally murdered. Setting out on the open road to find his family’s killers, Max rampages across The Outback slaughtering anyone involved.
Lady Vengeance

After serving 13 years for the kidnapping and murder of a young boy, Lee Guem-ja begins her life anew. Secretly, with the help of some of her fellow inmates, she also plans her revenge against the man who was really responsible for the murder of the boy.

Enable Remote Disk Browsing on a Mac

Alex — Wed, 31 Aug 2011 14:04:22 +0000

I recently bought a blu-ray drive for my PC to be able to watch movies and burn blu-ray disks easily. Sadly, Apple doesn’t offer a Mac with a blu-ray drive nor have I found a blu-ray internal drive for Macbook Pros.

One thing that is available for Macs is called ‘DVD or CD Sharing’, also called ‘Remote Disk’. You can find the default instructions on how to set it up over at Apple’s support article. The instructions include how to install the DVD or CD Sharing client on a Windows PC for sharing to a Mac.

What isn’t included in those instructions is the fact that by default, only Macbook Airs and Mac Minis support Remote Disk out of the box. I guess this is because they are the only two Mac models that don’t have optical drives.

Once DVD or CD Sharing has been enabled on a remote system (and the firewalls between the two systems correctly configured), the following two lines will activate the ‘Remote Disk’ option in the Finder window. Run them in a terminal window, then restart your computer.

defaults write com.apple.NetworkBrowser EnableODiskBrowsing -bool true
defaults write com.apple.NetworkBrowser ODSSupported -bool true

After boot, you should see the following options in your Finder.

Note: My PC has two disk drives shared in the above picture.

Augeas Lens for Modifying Munin Nodes

Alex — Thu, 11 Aug 2011 21:14:28 +0000

Augeas (from EPEL) doesn’t come with a default lens for the munin-node.conf files that control Munin Nodes. So I whipped one together.

(* Munin Node module for Augeas *)

module MuninNode =
  autoload xfm

  let record =
    let value = store /[^ \t\n]+([ \t]+[^ \t\n]+)*/ in
      [ key Rx.word . Sep.space . value . Util.eol ]

  let lns = (record | Util.comment | Util.empty) *

  let filter = incl "/etc/munin/munin-node.conf" . Util.stdexcl

  let xfm = transform lns filter

AlexCline.net

“Message: dualvar is only available with the XS version of Scalar::Util” Error in CentOS 5

Sending HTML Email from the Linux Command Line

Stop PIPA/SOPA!

Reconfiguring Network Interfaces in CentOS/RHEL Systems Cloned with vCenter

MySQL “duplicate entry for ’127′ for key 1″ in Rails

Disable nouveau drivers in Fedora 15

1955 – 2011 Steve Jobs Dies at 56

Violent Revenge Thrillers Worth Watching

The Man From Nowhere

Man on Fire

Taken

The Crow

Hanna

Léon: The Professional

Oldboy

The Horseman

Mad Max

Lady Vengeance

Enable Remote Disk Browsing on a Mac

Augeas Lens for Modifying Munin Nodes