Archive
Posts from 2010
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 →Forcing your Linux users to use strong passwords
All SysAdmins know the importance of using strong passwords. These are the life blood of our systems, since a weak password will allow an adversary to enter our systems with a minimal amount of work. There are dozens oftools that can generate strong passwords, as well as a number of tools that can be used to force users to select strong passwords when they change their passwords. The most common way to enforce strong passwords is through the pam_cracklib.so PAM plug-in…
$ 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 →Making sense of the various routing / firewall solutions that are available
I am currently running dd-wrt at home. Dd-wrt works pretty well, but I recently started to do some digging to see what other routing / firewall solutions existed. There are a bunch of routing / firewall gateway solutions available, and each one provides a unique experience. Some run on Linux, some on OpenBSD, and others on Linux…
$ read more →Locating the SSH key type and key size from a public key file
One of my friends sent me an e-mail earlier this week inquiring about SSH keys. Specifically, he wanted to know how he could determine the type of key and the key-size in a public key file. All openssh implementations ship with the ssh-keygen utility, which has a "-l" option that can be used to print the type of key, the size of the key and the key's fingerprint: I needed to summarize all of the keys on some systems I managed a few years back, and found a new friend in ssh-keygen.
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