Daily Archives: May 1, 2012
I recently installed an update of a software package running on an Amazon EC2 host.
In the configure step I found there was an unsatisfied dependency: it wanted ossp-uuid, which was not available on the system. Neither was yum able to find it: there was an alternative uuid, but no hint of anything from ossp. Turned up some problems with yum too (a hung security-update process from weeks ago and a corrupted database), but that’s another story. Checking my box at home, the reason I hadn’t stumbled on the dependency is that ossp-uuid is installed as a standard package here. A case of different distros having different packages in their standard repos.
In the absence of a package, installing from source seemed the obvious thing to do. So I made my way to ossp.org, from where navigation to an ossp-uuid source download is easy. Reassuringly I see Ralf Engelschall is in charge (whois lists him too), but worryingly none of the packages are signed. A summary look at the source package reassures me it looks fine, though I don’t have time for exhaustive review. In the unlikely event of a trojan package having found its way to the site, I expect some reader of my blog will alert me to the story!
Anyway, that’s getting ahead of myself. The unexpected problem I faced was actually downloading the package, which is available only through FTP. Firefox from home timed out; lynx or perl GET from the ec2 machine returned an unhelpful error. Looks like a firewall in the way of FTP building its data connection. Installing an old-fashioned commandline ftp I found neither active nor passive mode would work, meaning neither the client nor the server could initiate the data connection.
Before going into an exhaustive investigation of those firewall components over which I have control (my router being #1 suspect at home), I decided to try other routes. The problem was resolved when I was able to access the FTP server from my own (webthing) web server, then make the package available over HTTP from there to the ec2 box.
In the Good Old Days™ before the coming of web browsers and bittorrent, FTP was THE protocol for transferring files. In 1990s web browsers it shared equal status with HTTP and others, and even into this century it was widely seen as a superior protocol to HTTP for data, particularly bigger files.
Now by contrast, the widespread use of blind firewalls requires me to jump through hoops just to use the protocol. The rant I once published about everything-over-HTTP is coming to pass, and is not a good thing.