High Tech Sorcery

I have been looking to various GNU/Linux distributions to determine their level of support for Xen.  Here’s what I found:

• Debian Etch – Xen Hypervisor 3.2.1 (via backports), Linux kernel 2.6.26 (via backports)
• Debian Lenny – Xen Hypervisor 3.2.1, Linux dom0 kernel 2.6.26
• Debian Squeeze (testing) – Xen Hypervisor 3.4.2, Linux dom0 kernel ???
• Ubuntu 8.04 (Hardy) – Xen Hypervisor 3.3.0 (via backports), Linux dom0 kernel 2.6.24
• Ubuntu 8.10-10.04 (Intrepid-Lucid) – Xen Hypervisor 3.3.0, no Linux dom0 kernel
• OpenSuse 11.2 – Xen Hypervisor 3.4.1, Linux dom0 kernel 2.6.31

As much as I like Debian and Debian based distros I think OpenSuse is probably the best platform for hosting Xen at the moment.

I think Ubuntu 9.04 is the only version of Ubuntu suffering from this bug but it appears as though no fix for this serious regression will be forthcoming.  To get pygrub to work you actually have to fix a bug in the python 2.5 curses library.  Open “/usr/lib/python2.5/curses/__init__.py” and add the following lines starting at line 17:

import os as _os
import sys as _sys

After that pygrub should work correctly.  More information about this bug can be found in launchpad bug #395321.

Just got done helping a user debug connection problems using FileZilla to connect over SFTP/SSH.  I noticed, sadly not immediately, that the username he was using was being send with an extra space at the end and thus was an invalid user.  I’m not sure there is a valid reason not to trim/strip whitespace from the beginning and ending of a username.  But this is something to be aware of.

The term search engine is particularly vague.  It can mean an online search engine, or it can mean software that provides something similar to the online search engines, or it can mean software that does fulltext indexing and querying.  I specifically wanted to find a tool that could be used to create a niche search engine without having to write the whole thing myself as a ruby on rails app.  Here’s what I found:

• mnoGoSearch – seems very actively maintained, packages present in Debian and Ubuntu, written in c
• DataparkSearch – seems fairly actively maintained, apparently a branch of mnoGoSearch, written in c
• Nutch – seems fairly actively maintained,written in java, built on top of Lucene

And that’s really it.  There is a product called ASPseek but it has long since been abandoned.  There is also ht://Dig but it has not been updated in years and is not really in the same league as the above.  So, at least for anyone trying to research this area there are not a whole lot options to try.

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I sent this to a client who didn’t know how to enable remote desktop administration in windows.

In the olden days one had to use packages such as scponly and rssh in order to restrict a user account to just being able to use scp and sftp.  Now that functionality is built into OpenSSH.  A client wanted me to setup such an account for 1 user on a system.  I modified sshd_config like this:

Match user username
  ChrootDirectory /home/%u
  ForceCommand internal-sftp
  X11Forwarding no
  AllowTcpForwarding no

Note that this only works in Ubuntu 8.10 and later and Debian 5.0 and later.  Also, be aware that the home directry has to be owned by root and not writable by the user for security reason.  So a directory inside the home directory will need to be created for the user to upload any files.

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I believe this is my 6th blog.  So far I have never taken the time to migrate articles from one to another and I am continuing that tradition.  Not so good for the internet perhaps but better for me to not have to take the time to get a migration right.  I may go back and report some of my older content as appropriate though.  I decided to use wordpress this time because I’m supporting some other wordpress users.  I haven’t been the biggest wordpress fan in the past but I’m willing to give it another try.