Block Device Problems

[John Kebbel]

#1 Thank you for the yum / bluefish help, mascarasnake. You solved my
specific problem (bluefish is now up and running) and gave me the key
(almost everything is Linux/Unix will be in the configuration files) to
figuring out lots of other issues. 

#2 I had a memory stick and a zip disk configured and running fine
(thanks to people in this mailing group) but now they're refusing to
work: what used to be valid block devices aren't valid anymore. Before I
tackle the specific problem, I'd like to increase my understanding of
this block device business. hd stands for hard drive and sd for scsi
drive, but for some weird reason usb drives have to pretend to be scsi
devices, etc. Can someone point me towards a tutorial that explains this
in detail and then works up to troubleshooting problems with block
devices?