thesauri sapientiae et quisquiliae
linux
Linux-related posts
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 …
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.
Broadcom 43xx Wireless Card in Linux
3Today I finally resolved what has been one of the most frustrated Linux issues I have faced yet — getting my bloody Dell Truemobile 1300 wireless card (stock in my Dell Inspiron 5100 notebook) to function in Linux. The problem has been that those bastards at Broadcom — the corporation that manufactures the controller for the card — have not released Linux drivers for this controller. Prior to today, I have struggled trying to wrap my Windows driver in a piece of Linux software called ndiswrapper. I have, as it turns out, found two ways to finally get the blasted card to work! (more…)
recently on cg.com