Saturday, September 07, 2013

The Linux Adventure Part 3: A Path to Success

Installing MySQL on the Diskstation

Continuing from the last installment: there are several items I listed on the to-do list that actually were already done. I didn't need to install MySQL on the Diskstation as it is already on there and enabled either by default or when I first configured it at setup.

Installing Bash on Ash

From the last installment, I had already installed the ipkg package management software. The command ipkg install bash will pull down the bash shell and install it on the Diskstation.

Test Manual Run of Existing Script

In preparation for the script test I first ran /opt/sbin/vpnc . This opened a connection to my client's VPN.

I then copied my existing bash script over to the Diskstation. But ran into several issues when trying to execute it. I had to relearn simple things like making sure the path was a part of calling a script unless it was already in the working directory (pwd shows current working directory).

I also had to learn new confusing things about Linux since a few confusing things weren't enough.

I made bash the initial shell by adding a few lines to the root profile to launch the bash shell. You can find these on the Synology Google hits for "Synology bash" but even after now getting the bash prompt when signing in (bash-3.2#)I still had to use special syntax to run the bash scripts through the bash shell.

In other words, I installed the bash shell, got it to be the default when logging in, but still the scripts will try to run under the Diskstation's native ash shell []. Got that? Thank you so much Linux. So upon initial attempts to run I would get beautifully intuitive syntax error messages like this:
Line 15: syntax error: unexpected "("

Using parenthesis when defining variables indicates you are using an array to store the value. I don't know many languages that don't support parenthesis or arrays, but because ash is designed to be super lightweight it doesn't quite have all the same functionality as bash. Here is a thread [] explaining that ash doesn't support arrays. You can take a look at the documentation for ash []. It's pretty amazing considering its tiny footprint.

But rather than look for ways to reinterpret the script in ways compatible for ash, I found some other people had similar problems. Ipkg installs bash under /opt/bin and you have to execute the bash script almost like a parameter to the bash command. Like so (where the working directory is the location of the script):
/opt/bin/bash ./

This now made the Diskstation try to execute the script, but I was not home free yet. There were some calls in the script to commands such as mysqldump and mysql, and both of these also needed to be prefaced with their directory locations. So I updated the script by adding /usr/syno/mysql/bin to the front of those command calls.

Now the script started to run, but I got one last error before it would complete the backup. The Diskstation told me it couldn't find the destination database on MySQL localhost where I would be copying the source database to. So I launched phpMyAdmin (a Diskstation natively supported package) and connected to the localhost server, then simply created an empty database for the backup.

It Works! I've Finally done Something that Works!  

    - Doc Brown (Back to the Future)

Now I ran the script and it worked just as it had on my laptop, reaching out via the VPN to the client database, grabbing the tables it needed, and copying them to the Diskstation. Awesome. Additional tips:
  • The Diskstation's MySQL installation is found at /usr/syno/MySQL/bin
  • The Diskstation's MySQL localhost server stores databases at /volume1/@database/mysql 
Now I have opened up some options and benefits for this task. I have:
  • Multiple ways to back up my client's database
    • mobile notebook
    • desktop at home
    • remotely connecting to the Diskstation
  • Increased my knowledge of the Diskstation and my love for Linux's idiosyncrasies
  • Gained a backup of the backup (the Diskstation utilizes mirroring)
There are a few things left to do before the process is fully automated. I need to add the vpnc commands to the script if possible so I don't have to do those manually. Also, add error handling to that if something goes wrong the script will correctly tidy up after itself, closing the vpnc connection and exiting the script.

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