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I have been fighting a problem with mounting volumes from an NFS Server in AWS for a few days. With more pressing issues at hand, I had to try and google for solutions for an hour or so before bed, and nothing I was doing was having any effect. Curiously, an Ubuntu based machine that was mounting the drive using NFS3 was not having the same problem. Only the Amazon Linux servers that were using NFS4 were having the issue, and were showing all files and directories as being owned by nobody:nobody.



I had previously insured that the user UID and group GID for the user that would be writing files (in my case "apache" was the same (with the same UID and GID) on the NFS server and the servers mounting the nfs volume.

As it turned out the problem was with the configuration (or lack thereof) of the rpcidmapd service. NFS4 relies on this service to map users between machines. The "idmapd" requires that the domain of both the client and server should match for the UID/GID mapping to work, and in my case it wasn't. Probably many people with proper DNS configuration don't hit this problem, but we did not have a proper DNS setup, as these machines are part of a growing cluster. Compounding the problem I had set the configuration files to have meaningless host names rather than a domain.

You can tweak this setup by editing the: /etc/idmapd.conf file, and find the "Domain" variable:



Set these to be the same for the server and all the clients.

The last problem was that I had to restart the idmapd process, which has an /etc/init.d control script named /etc/rpcidmapd



Restart the process on both the nfs server and any nfs clients. If the source of your problem is the same as mine, your user & group mapping problems should be solved:



Finally!!!!

This error pops up for a couple of reasons. At the top of the script there will probably be a line that looks like this:



This is telling Linux that this script should be interpreted using the /bin/sh program. So your first step is to verify that program exists. I tend to use:



This will typically come back with a response like this:



This is telling us that the path to the sh program is in fact /bin/sh, matching the path specified at the top of the script. Ok, so what gives? Well, it's possible that this script was made on an operating system that has line ending characters different than linux. This could have been on on a Mac or PC, or the file could have been converted when it was packaged. In this case, you get the relatively misleading bad interpreter: No such file or directory message, which is really trying to look for sh, although you don't get any indication of the fact.

So, how to fix? Read on. Continue reading "Linux shell scripting: bad interpreter: No such file or directory"

Having recently left a company that had Exchange, the removal of Goodlink from my Samsung Blackjack left the phone in a fairly broken state. I fixed this by doing a full reset (Turn on phone while holding Up Arrow) and choosing 1. This put things back in basic working order.

My efforts to use the built in email client to access my Courier IMap Email had never been successful, so I decided to explore AT+T's XPress Mail system. This consists of client software you install on the phone, and a desktop application that connects through AT+T's servers to give you access to your email remotely, and also can be used to give you access to files on your PC.

Upon install of the client you choose your mail server (in my case IMAP) and input the basic settings required by most IMAP client softare (Account name & Password, email address, the IMAP server, SMTP server, security settings, etc). I did notice an unusual configuration box asking for "Root Folder Path" which I left blank. Here's where the fun began.





Continue reading "AT+T Wireless XPress Mail Courier IMAP setup problem - Trash Folder?"

I gave a talk on the use of Xen for web developers at Lampsig. It took me a while to get my notes transcribed, but here at last they are. This prescription has been used by me to install Xen successfully on a Fedora core 4 box, Centos 4.3 and 4.4 boxes, and should probably work on RHEL, assuming you can figure out how to get the packages you need.

I cover use of file backed file systems, and how to mount and edit them, as well as expanding a file based filesystem.

I have run gentoo and Centos guests I got from jailtime.org and have found them to be very stable. I even was able to use this on a 64 bit server, although I did have to build my own guest. Many people who have had trouble getting Xen to work reliably when using the packaged (rpm) versions of Xen may find this prescription fixes their problems.

Xen 3.0 Centos How-to

I recently had need to add XWindows to a Centos 4.x install that didn't have X or Gnome. I was doing this under VMware which added slightly to the degree of difficulty. As it turns out, using Yum makes this a very easy process, although you probably end up with some bloated packageware.



Pay close attention to the capitalization -- Yum is picky. "Gnome desktop environment" won't work, for example.

I'm attending the Southern California Linux Convention this weekend, along with other members of Lampsig. Folks are rabid for information on LAMP as illustrated by this shot of the Lampsig booth.