Had an interesting issue today working on a mod_proxy setup of Apache forwarding requests in a reverse proxy setup to a backend Tomcat server. No matter what I did, I kept getting this in Apache's error log:
[error] (13)Permission denied: proxy: AJP: attempt to connect to 10.x.x.x:7009 (virtualhost.virtualdomain.com) failed
How many times have you ran through this series of events?
$ cat ~/.ssh/id_dsa.pub
...copy output to clipboard...
$ ssh myhost
...enter password...
myhost$ vi ~./ssh/authorized_keys
...paste public key and save...
myhost$ exit
Thanks to bash's tab completion, I happened upon ssh-copy-id. Instead of all that above, just do this:
$ ssh-copy-id myhost
...enter password...
Another one of those topics where about 50% of the class bustled in excitement over learning something new and simple came up today. After running fdisk, you will almost always get an error about the kernel not using the new partition table you just modified. Before GNU released parted, you had to reboot in order for the kernel to purge it's cache and reload the partition table, but now, all you need to do is run partprobe after exiting
During my RH300 course, my instructor mentioned that RHEL 6 is likely to come out sometime Q1 2010. I wanted to know more about it, so I hit Google, and came up with some interesting results.
This week, I'm off to my RH300 course which involves taking my RHCE exam on Friday. It's funny -- studying one thing from 9-5 without any distractions or multitasking truly feels like a vacation to me. After 5pm, I go back to my room and play. I'm pumped! Wish me luck!
Like most, I learned shell scripting by following examples. Well, unfortunately, most of the samples I learned from used the 'seq' binary to execute a simple for loop like so:
for i in `seq 1 10`; do
echo $i
done
I discovered why this is bad today - not all Unixes (Solaris and Darwin included) come with it. Not to mention we're forking a process where we don't need it. On bash, use the built-in brace expansion instead:
It's an item that I feel hasn't got much press, at least in the limited RSS entries I've had time to scan lately: Nagios has been forked. I've been using Nagios long enough that I actually used NetSaint for a bit, so I have some mixed feelings about Icinga. In general, I'm all for forks when they are indeed needed - FOSWiki is a great example. But forks shouldn't be taken lightly, in many ways they are like a divorce - they should be a last resort, not a quick way out. Personally, I think that the fork will ultimately either fail or merge back into Nagios, but read on for why I think the Icinga fork is a case of two wrongs making a right.
Running GUI's over an SSH tunnel is nothing new, and not too tricky. However, I recently had a case where I wanted to run a java-based GUI (dhcpmgr) as root on a remote host, and have it display on my local Linux box. I hit a couple of snags, so I thought I'd post them here to hopefully help out others.
I'm not for sure when they did it, but the RHEL folks made it a bunch easier to setup simple source policy routing. By using source policy routing, we fix the issue of firewalls freaking out when the reply packet to a host leaves a multihomed host on a different interface than what the request came in on. In prior versions, you had to setup some custom scripts, but that's no longer the case - all the hooks are there in the OS now.
Another one of those topics where about 50% of the class bustled in excitement over learning something new and simple came up today. After running fdisk, you will almost always get an error about the kernel not using the new partition table you just modified. Before GNU released parted, you had to reboot in order for the kernel to purge it's cache and reload the partition table, but now, all you need to do is run partprobe after exiting 
During my 
