teh fear

This may not apply to more recent versions of xen and centos, however, running kernel 2.6.18-xen_3.1.0 on CentOS 4.5 I have found that port redirection doesn’t work as expected.

SpamAssassin is a great tool for filtering out spam email from the rest, and spam email is a real pain these days.
spamass-milter is a sendmail filter that can be used to connect spamassassin and sendmail together (it is one of many different ways, others include amavis and procmail).
spamass-milter is fine if it is being used [...]

when first booting xen most people like me (who like to ignore most ot the manual reading until later) will find a xen warning about the thread local storage libraries and how they access memory in a way that xen makes slow. The warning offers the following advice on how to disable it:
mv /lib/tls /lib/tls.disabled [...]

Everytime I need to change something on a co-located server (ours are only about 2 miles from the main office, but it is still a pain if one has to go to the site because a server is not booting up) that requires restarting in a new configuration, I’m always worried that something might not [...]

Mounting a loop file that is a filesystem is no problem
losetup /dev/loop0 my_loop_image
mount /dev/loop my_mount_point

or
mount -o loop my_loop_image my_mount_point
BUT, what if my loop image has partitions?

A file, key to the successful boot of many a linux system is the initrd image.
It used to be a simple gzipped loop filesystem, unpacked and mounted by commands similar to
gzip -dc initrd.img > initrd_unzipped.img
mount -o loop initrd_unzipped.img temp_dir
Then files can be tweaked inside ‘temp_dir’, the image is then updated by
umount temp_dir
gzip -9c initrd_unzipped.img > [...]

Having started to play with xen on linux, I have begun to use loop filesystems (a filesystem embedded in a file) rather a lot.
Xen virtual servers are, fairly often, run from within a loop filesystem and generally start with a fairly small file (1GB is big for a normal file, but not when it is [...]