A number of current distributions of OpenSSH default to storing hostnames and IP addresses in ~/.ssh/known_hosts in a hashed form,in order to make it harder for an intruder to work out where elseyou have an account on that you access from this system (this is the HashKnownHosts option for ssh ). Since I recently wound up digginginto this and the details are underdocumented, here's what I know abouthow this works.

The summary is that this is your traditional one-way

My Fedora 8 problem is that I still have a machine running Fedora 8,which means that I need to upgrade it. Worse, this is not some disusedmachine sitting in the corner but my home workstation; it doesn't havemuch bandwidth, and I kind of want it to be up and usable as much aspossible when I'm home. So I've been gloomily contemplating my upgradeoptions for some time.

The officially supported or semi-supported way to do this is to do theupgrade

I recently mentioned in passing that if I wasbuilding a file based blog engine today, I would do a number of thingsdifferently than they are now. Given that file based blog engines are eternally popular , here's my list of thosethings.

First and foremost, I would not use file metadata for anything, mostespecially the file date. Using the date of an entry's file as theentry's date is superficially attractive but in practice it complicatesyour life quite a bit and it clashes badly

I mentioned this in passing recently ; today I feellike elaborating on why replacing a distribution package with your ownlocally built version of something is a big pain in the rear and thuswhy sysadmins almost never do it.

(I'm going to assume here that you're familiar with building fromsource in general.)

First, you have two options for how to do this; you can build fromsource and just do a ' make install ', or you can actually (re)build anew package

These days, an increasing number of storage appliances can do both NFSfileservice and iSCSI (generally using the same underlying pool of diskspace), which has resulted in me seeing an increasing number of peoplewho are wondering which one they should use.

The summary of my answer is that iSCSI is a SAN technology and NFS is afileservice technology. If you want to add storage to a single machine,iSCSI will work acceptably well; if you want to share files among abunch of machines, you want NFS.

Recently, some of our Red Hat Enterprise Linux systems started mailingus a message from cron once an hour:

/etc/cron.hourly/mcelog.cron:

mcelog: warning: record length longer than expected. Consider update.

There are two things wrong with this message. The first is a RHELbug; Red Hat should have made sure that this cron job didn't bombardsysadmins with unimportant messages by, for example, redirectingstandard error to /dev/null .

(This is sadly a general problem

I have a problem. It's not a unique or novel problem; I understand it'sone that a lot of people have. My problem is that over time my emailinbox quietly winds up getting used as my to-do tracker, basicallyregardless of how I'm theoretically trying to keep track of this stuff.I leave messages in my inbox to remind me to do things, and the latestgo-round of this has now reached the point where I email myself notesabout things I want

One of the reasons that I'm not too enthused with various schemes to put /etc under version control is that they don't really give me what Ireally want out of the whole exercise.

First, let's assume that you have somehow divided your /etc repositoryup into a lot of separate modules in orderto keep things straight. Without loss of generality we can look onlyat the evolution of a single module on a single system over time. Theproblem is that you really have three separate

We recently went through the experience of upgrading all of our ZFSfileservers from Solaris 10 update 6to Solaris 10 update 8. This took somewhere around twenty minutes ofdowntime per fileserver, most of which was waiting for ZFS pools toslowly import.

You might wonder how we got an OS upgrade to go so fast. The answeris that we cheated, twice.

The first way we cheated is that we didn't upgrade the OS; instead, we(re)installed Solaris 10 update 8 from