Monthly Archives: May 2013

CentOS 6.4 Installation failed due to ACPI errors

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I got the latest CentOS (6.4) iso to install on my Toshiba Satellite laptop. It’s a few years old, but still works great, and I found myself hardly ever using the Windows 7 install. Unfortunately I ran into a bunch of AE_NOT_FOUND and ACPI errors, always causing a kernel panic. I tried a few different versions, including 6.2 and 6.1 that I already had with the same results. Oddly enough, I downloaded and successfully installed Ubuntu 13.04 64bit, but not wanting that to be my distro, I tried again, this time hitting [tab] at the install menu, and adding “acpi=off” at the boot line, and viola, that did the trick. For some reason the acpi driver is causing a system panic. Once the OS is installed and configured I’ll see if I can get it to turn back on. It can be very useful on a laptop.

Update: acpi=off worked for the CentOS installation, but once it was installed I could not boot. I was able to do this to turn acpi back on (otherwise it can cause your fan to stop working, causing a hang due to overheating):

acpi=enable pci=assign-busse acpi=ht

This successfully allowed my system to boot. Once it is completely booted, I will need to update my grub conf to ensure the settings are persistent.

Clearing /tmp and /var/tmp with find in cron.daily

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Moving from Solaris to Linux has been enriching, but not without subtle differences. One of many was the need for older SLES servers to clear out /tmp and /var/tmp. I started with the standard Solaris cron jobs:

/usr/bin/find /tmp/* -mount -depth -mtime +30 -a -exec rm -rf {} \; > /dev/null 2>&1
/usr/bin/find /var/tmp/* -mount -depth -mtime +30 -a -exec rm -rf {} \; > /dev/null 2>&1

In spite of how active some of these servers are, if /tmp or /var/tmp are empty, the above commands return a value of 1 instead of 0, thus resulting in a nice email that cron failed. Removing the asterisk was an easy way to fix this, however that posed the problem of deleting /tmp or /var/tmp itself if there was no activity on the server for 30 days. Unlikely, but possible. Rather than touching a file before the find commands (thus moving mtime to current), I opted to exclude directories and only remove files (adding the -type f option). Even though directories can still exist, they take up very little space and will likely get cleaned up on a reboot at some point. This was a happy medium. My script now looks like this:

/usr/bin/find /tmp/ -type f -mount -depth -mtime +30 -a -exec rm -rf {} \; > /dev/null 2>&1
/usr/bin/find /var/tmp/ -type f -mount -depth -mtime +30 -a -exec rm -rf {} \; > /dev/null 2>&1

Fixing a Permalink problem in WordPress

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I wanted to post this because I saw quite a few people having the problem that I was having. I managed to find one thing that caused my problem, as opposed to disabling this plugin or that plugin, none of which I had installed.

The problem:
When changing the default permalink configuration from ?p=5 to /2013/05/my-cool-post, all of a sudden the links to both the posts themselves and to the comment buttons were giving 404 errors. After much searching.

Supporting Evidence:
Some people reported having multiple sites hosted in the same wordpress account or hosting account, but only having this problem with 1 site. This tells me that it is specific to the site, not the hosting provider, or even WordPress. That’s what led me to the solution.

The solution:
While perusing through the httpd.conf file on my system, I was looking at the following:

<Directory />
    Options Indexes FollowSymLinks Includes +ExecCGI
    AllowOverride None
</Directory>

Notice that “AllowOverride None” is set, which basically disables mod_rewrite (an apache module necessary for WordPress to be able to rewrite your urls — ie use Permalinks). I changed this to “All”, and restarted httpd, but still had the same issue.

Finally I went through and searched for “Directory”, and there are quite a few of them in there, but then I found another stanza:

<Directory "/var/www/html">

With quite a few comments inside of it. (That’s why I didn’t notice it the first time around.) Inside that Directory stanza, was this:

AllowOverride None

This one was overriding the “/” directive earlier, so as soon as I changed this from “None” to “All”, and restarted httpd, my links worked perfectly afterward.

I hope this helps you guys, it seems to be a chronic problem in WordPress.

Trying out new Linux distros

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One of the last things I usually want to do is take something that works and put it at risk. That’s always how I feel when I’m upgrading any of my Linux systems at home, putting the whole thing at risk. The result: an installation of Ubuntu 10.10 that is no longer supported. Even the old-releases repos don’t have the updates that I want anymore. Nevertheless, I felt it was time for a change.

In the past, this would have meant either removing the drive and replacing it with another, or rolling the dice and just installing over top of my old OS, hoping that I copied all of those files I wanted.

Some time ago I started using Virtualbox, a free download from Oracle. For anyone who is not familiar with Virtualbox and the like, it’s a virtual platform for installing other operating systems.  You take a chunk of your host hard drive (the physical disk in your computer) and create a “virtual disk drive” that you can use as the boot disk for your virtual installation.

Aside from having a variety of operating systems at my fingertips with just one physical system, it also lets me “try before I buy” new distributions, and see how things look and feel before I commit to upgrading my existing Linux system. So far I couldn’t be more pleased, because some of them were discarded, and it’s as easy as right click/Remove, and viola, it’s gone.  You have the option of keeping the VDI (Virtual Disk Image) around, but if I’m trashing a virtual machine, I doubt I’d want the disk image again, so I always opt to save the space.

I just downloaded the newest Ubuntu, 13.04, so I can test it out before I commit…. I’m not a huge fan of Gnome 3, but I’m willing to try it for a while, since I mostly use CLI with screen.