thesauri sapientiae et quisquiliae
Posts tagged SEF
Superfluous fstab Entries After Upgrading to Lucid LTS
0A quick post to outline a stupefying problem I encountered after upgrading one of my machines to Ubuntu Lucid (10.04) this weekend. By way of background, I am anything but an early-adopter of OS releases — especially on my production hardware. I haven’t the time to debug network-critical software on systems on which I rely heavily, so I typically lag a major-version-release or so behind the “cutting edge”.
Yesterday I finally made the move to upgrade to Lucid LTS on one of my servers on my home network. The automatic upgrade apps downloaded and executed without a hitch, so I was optimistic upon reboot. For reasons which surpass understanding, however, I received an error indicating that the hard disk upon which I had installed the OS refused to mount at boot time — although, to Lucid’s credit, I was given an option to skip this mounting and continue with the boot.
The whole episode was absurd, as the disk was clearly mounted and booting — how else was the OS loading at all if the disk upon which it resides would not boot? Upon logging in, a quick cat /var/log/boot.log suggested that there was, indeed, an error in mounting /dev/sda1. cat /etc/fstab made clear what the problem was — somehow there were additional entries in the fstab file which tried to mount the partitions on /dev/sda subsequent to their initial mounting. I’ve not the slightest idea how these entries made their way into the file. I am, however, confident that they were not there prior to the upgrade as this error was entirely new. A few keystrokes in vim and I had commented-out the offending entries. Upon reboot, all was well with the server.
Most perplexing …
Ubuntu in VirtualBox
21001 days
by captivus
in General Posts
I travel nearly every week to my clients’ offices. I have recently become quite keen on the idea of videoconferencing with my wife and children each night, as a means to span the miles between us. Skype is the software I’ve settled on, as the most promising open-source competitor (Wengo) didn’t instill much confidence. The firm I work for blocks Skype installation through its use of McAfee’s enterprise product — a fact which makes me a saaaad panda! (If this turn of phrase is foreign to you, might I suggest viewing the South Park episode from which it emanates?) (Tangentially, my firm is also staunchly anti-open source, as evidenced through our open source software policy — a fact which makes me an equally bereaved bear!) I digress …
The solution to my predicament? Sun’s brilliant VirtualBox open source virtualization package running the latest Ubuntu release — currently 9.04 (or “Jaunty Jackelope,” as they call it). The installation of VirtualBox took a bit on my lappy, but it went fairly seamlessly. The only hitch was that the installation of the VirtualBox Host-Only Network adapter in Windows XP SP3 broke my wireless networking. (It may well have broken all networking, but I didn’t try plugging a cable in to check.) The solution to this was fairly simple — disable the newly installed adapter! It seems that VirtualBox doesn’t need this adapter enabled in order to provide the virtual OS networking. (I’ve no idea what this adapter is used for at the moment. Perhaps I’ll figure this out as I work with VBox a bit more.)
The only Ubuntu image I had lying around was a Hardy (8.04) disc I burned some time ago. I added a new machine to VBox, installed Ubuntu from the disc, updated to Jaunty using apt, and installed Skype from the Medibuntu repository. So, I’ve got a virtual Jaunty up and running and, I must say, it is bloody fantastic! Good show, Sun!
DD-WRT on the WRT54G v8
0DD-WRT is, by far, my favorite third-party firmware for the Linksys WRT54G wireless router. I, personally, have three of these on my network — one as the primary access point and router and two as bridged repeaters — on which I have used several versions of dd-wrt. (I’ve also used Sveasoft and Hyper-WRT on these devices.)
Previously, I have endured spectacular failure when trying to flash version 8 devices. <The sound of bricks dropping rings out in the distance.> (My devices are all version 2. The Wikipedia article I linked to above explains the differences in the hardware versions.) It turns out, the critical misunderstanding I had related to flashing the stock firmware with vxWorksKiller (prior to transferring the DD-WRT image to the router via TFTP). I did not realize that the upload of vxWorksKiller needed to be done from a special management screen that is only accessible after unplugging the router, holding down the reset button while plugging the router back in, and continuing to hold the reset button for 20 seconds. This implies that the upload should not be done from the default firmware’s upgrade page. This understanding was gained this week when building a PC, and flashing two routers, for a friend of mine.
Given that the preponderance of WRT54Gs on shelves now are version 8.x, this realization bodes well for me in future purchases.
Core Dumps in Ubuntu
01110 days
I resolved this year that I would take time to pursue one of my passions — computer science. As such, I am learning how to write applications for Linux. I’ve just spent 30 frustrating minutes trying to figure out why on earth my deliberate segmentation fault in the small C program I have written is not producing a core dump in Ubuntu 9.04. It turns out that Ubuntu disables core dumps in Bash by default. The fix is simple enough — use the ulimit command to enable core dumps.
bash$ ulimit -c 100
In this case I have enabled core dumps and given them a limit of 100 blocks. Problem solved! Hopefully this makes it into the search engines and helps someone else frustrated by this same issue.
Addon Domains at HostGator
01775 days
by captivus
in General Posts
This site is, as I’ve mentioned previously, hosted on a Linux server I rent from HostGator. I ran into a bit of trouble when using “addon domains” with their service which I have meant to document for some time now.
I read the knowledgebase article at HostGator Support on setting up addon domains which warns at the top of the article:
“Before you can add an addon domain you must change the name servers for the domain name to the ones provided for your hosting account. You cannot create an addon domain if your DNS for the site you are trying to add hasn’t propagated yet.”
I was exact in following these instructions and waited 3 days for the DNS changes I had made at GoDaddy (where I purchased and manage the domains) to propagate. Ultimately, they did not.
The solution to the problem was to setup the addon domain at HostGator, via the cPanel, immediately after making the DNS changes to the domain. I’m not sure if this is an issue unique to GoDaddy domains — I imagine it is not. It seems that the documentation provided by HostGator is inaccurate in this regard.
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