Java won't work on Yosemite? Of course not.

Yet another reason to be grumpy about the upgrade to Yosemite.

I downloaded and installed jmeter to do some apache profiling/benchmarking, but it wouldn't run, complaining that there was no java. When you try to run a java application, you may get an error message that looks something like this:

To open "application" you need to install the legacy Java SE 6 runtime.

This is because jmeter requires the legacy Java 6 provided by Apple and you will need to download it. But it's simple enoug.

You can get the download from here: https://support.apple.com/kb/DL1572?locale=en_US

Just when you thought they weren't out to get you

el Capitan makes me go full screen! STOP IT!

Ever since I upgraded to OS X el Capitan (I'm behind the curve, I acknowledge), the little green button in the upper left-hand corner of all my apps and windows now does unexpected tomfoolery. Instead of maximizing or re-sizing the windows, like it did in all previous versions of OS X, the button takes into full screen mode. Suddenly everything that was maximized became uber-maximized, and it annoyed the bejeezus out of me.

Here's the fix. If you want to call it that.

Old school is better, in my opinion: just Option-Click on the green button. BAM, you're back to the comfortable old days, when green buttons just meant maximize.

vagrant problems with el Capitan.Simple fix!

Someone in the office yesterday shamed me into upgrading my Mac to el Capitan and it went as smoothly as you expect, with vagrant completely breaking.

Luckily, the fix is straightforward: el Capitan changed permissions of /usr/bin, so now you have to account for it:

sudo bash
cd /usr/bin
ln -s opt/vagrant/bin/vagrant

That should do it. You may have to uninstall and reinstall both vagrant and VirtualBox first. But those are simple things these days. Just like upgrading to el Capitan ...

How to ensure a perl file will call modules in the same directory

Suppose you call a perl script remotely, or from a different directory, perhaps through a shell script call or bash alias.

What happens if your script uses a perl package inside the same directory?

Simple solution:

#!/usr/bin/perl
use strict;
# ensure that this specific directory 
# is in the path of the script
use File::Basename;
use lib dirname (__FILE__); 

When your mysql server crashes and won't restart

This just happened to me: mysql went down for no apparent reason and I thought it was because I was missing with the .ini file. No matter how I tried, it wouldn't restart.

I checked the error logs and found:

InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
InnoDB: Unable to lock ./ibdata1, error: 11
InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
InnoDB: Unable to lock ./ibdata1, error: 11
InnoDB: Check that you do not already have another mysqld process
InnoDB: using the same InnoDB data or log files.
InnoDB: Unable to lock ./ibdata1, error: 11

This was an indicator that a mysql process was already running it, but I couldn't find it on top, or using

ps aux | grep mysql 

So I tried this:

# lsof -i:3306

COMMAND   PID  USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mysqld  24416 mysql   10u  IPv4 173905      0t0  TCP localhost:mysql (LISTEN)

# sudo kill 24416
# sudo /etc/init.d/mysql start

That's all it took.

In this case.

How to build a reverse ssh mysql tunnel

Suppose you need to connect to a mysql database on a server (the "DB" server) to which you have been firewalled out of. Not a problem if you can connect to a server (the "TUNNEL" server) that has been let through the firewall. No problem at all. It's a little bit of a problem. But you're stalwart.


Here's what you do:

1. ssh into the DB server:
   

   ssh YOU@DBSERVER.com
   

2. use the screen utility to allow you to detach your terminal, and still keep the tunnel open:
   

   screen
   

3. Open the tunnel to the TUNNEL server. Let's say you want to connect to the db server on port 3306. Pick an arbitrary port for your TUNNEL server (3316, for instance):
   

   ssh -R 3316:localhost:3306 YOU@TUNNELSERVER.com
   

4. You are now on the TUNNEL server. You want to keep the connection open, at that point, and can do a cheesy keepalive:
   

   while true ; do echo keepalive ; sleep 60 ; done
   

5. Now detach by pressing ctrl-A, then d. This returns you to the DB server but the tunnel to the TUNNEL server remains open.

That's it! Your reverse tunnel is open. If you want to connect to the DB server directly from the TUNNEL server, then your command is:

mysql -h 127.0.0.1 -u USERNAME -p -P 3316

If you are on another server, you will have to tunnel into the TUNNEL server first:

ssh -L 3308:127.0.0.1:3316 YOU@TUNNELSERVER.com

After that, you can connect with the command:

mysql -h 127.0.0.1 -u USERNAME -p -P 3308