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Posts in Linux
Using dnscap to debug DNS problems on Linux hosts
DNS can often make a SysAdmins life difficult, since a misconfigured entry or a broken authoritative DNS server will cause things to fail in odd ways. If you are fortunate enough to use Linux on your servers and desktops, you have a slew of utilities available to look at problems. I've discussed a few of my favorite DNS debugging utilities in past posts, and recently added the dnscap utility to this list. Dnscap is a command line utility that allows you to view ALL of the DNS requests sent over an interface in a dig-like or binary format…
$ read more →A simple and easy way to copy a file system between two Linux servers
During my tenure as a SysAdmin, I can't recall how many times I've needed to duplicate the contents of a file systems between systems. I've used a variety of solutions to do this, including array-based replication, database replication and tools such as rsync and tar piped to tar over SSH. When rsync and tar where the right tool, I often asked myself why there wasn't a generic file system replication tool when I completed my work. Well, it appears there is…
$ read more →The easiest way to test the memory in your Intel-based PC!
Most admins have a series of tools they use to check for faulty hardware. This toolkit most likely includes the ultimate boot disk, a network accessible memtest and preclear_disk.sh on a USB stick. I was always curious why Linux disitrubtions didn't integrate these items into their install / live CDs, since it would make debugging flakey hardware a whole lot easier. Well, I was pleasantly surprised this week when I booted the Fedora 14 installation DVD and saw the following screen: Once I selected the memory test option I was thrown directly into memtest: This is solid, since one CD can now be used to test the memory in a server and repair things that go south…
$ read more →Finding approximate matches in a data file with agrep
A few weeks back I ran into a situation that required me to locate a data given a file with various variations of that data. I proceeded to grep for each form of the string (e.g., "the", "the", "tte") I could think of, but wasn't getting the results I wanted. After a bit of poking around, I came across the incredibly useful agrep utility. This utility allows you to look for approximate matches in files, specifying the number of variations that can occur…
$ read more →Getting gnome to work after an initial CentOS installation
While preparing for my RHCE exam, I wanted to install of the system-config-* GUIs to see what functionality they provided. I used the yum groupinstall option to install the GNOME desktop: and then proceeded to add my preferred desktop environment to /etc/sysconfig/de sktop: Once these items were installed I ran 'init 5' and was greeted with the following message in /var/log/messages: After reading through various logs and scripts, I noticed that the gdm display manager wasn't installed. I thought groupinstalling the GNOME desktop would force a display manager to be installed, but alas that isn't the case. To get everything working I fired up yum and installed gdm: Everything worked as expected once gdm was installed, and I could fire up the GUIs without issue.
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