Category Archives: Ruby on Rails

Upgrading VPS Web Server from Ubuntu 10.04 to 12.04

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I am not a “real” system administrator but I manager sever VPS servers for my own web sites. This is what I did to update from Ubunutu LTS 10.04 to Ubunutu VPS 12.04.

  1. I already have all the code and databases backed up, off the server, regularly. I backed up various things to another machine: sites-available files, cron directories, .bashrc, .profile, keys.
  2. I tried running the preferred upgrade command

    [bash]do-release-upgrade[/bash]

    But got the message

    -bash: do-release-upgrade: command not found

    Then I ran

    [bash]sudo apt-get install update-manager-core[/bash]

    Then I was able to run [bash]sudo do-release-upgrade[/bash]

  3. Which resulted in this somewhat scary message

    This session appears to be running under ssh. It is not recommended to perform a upgrade over ssh currently because in case of failure it is harder to recover.

    If you continue, an additional ssh daemon will be started at port ‘9004’.
    Do you want to continue?

    I look around on the web for advice. What’s the risk of upgrading over SSH? seems a good recap. I then continued. I then got this message

    To make recovery in case of failure easier, an additional sshd will be started on port ‘1022’. If anything goes wrong with the running ssh you can still connect to the additional one.
    If you run a firewall, you may need to temporarily open this port. As this is potentially dangerous it’s not done automatically. You can open the port with e.g.:
    ‘iptables -I INPUT -p tcp –dport 1022 -j ACCEPT’

  4. 12 minutes after the upgrade started, the download was complete and I got a message to decide if I wanted to manually approve every restart required or just automatically approve them all. I chose the option to have all restart automatically.
  5. Then lots of files were installed and I was asked about various files; where I (or some script) had changed (or deleted) the default file and now the upgrade wanted to replace the existing file. I had to guess what to do in those cases. They let you look at the diff between your existing file and the proposed overwrite. I think I would like it if they default behavior was to create a backup of the file in that same directory (you choosing whether to set your file or the updated file as active).

The entire process took exactly 30 minutes, with the system restarting in Ubuntu 12.04.

Thankfully the upgrade seems to have gone without causing any problems. This is normally the case. But, even with a very small likelihood of encountering issues it is worrisome as those issues might pose some serious problems. Especially for someone with very limited system administration ability.

I am extremely thankful for all the programmers that created the code to make this process so straightforward and reliable.

[bash]lsb_release -a[/bash]

lets you see the current Ubunutu version you are running.

When I updated a server that had Ruby on Rails applications everything almost worked fine. Passenger was unable to load the application talking about

libmysqlclient_r.so.16: cannot open shared object file: No such file or directory – /usr/local/rvm/gems/ruby-1.9.2-p290/gems/mysql2-0.3.11/lib/mysql2/mysql2.so

I was able to find the solution to that issue was to uninstall the mysql2 gem and then run bundle update: which worked great. The uninstall would work for me unless I was actually root (sudo didn’t work), so I used su to login as root and then

[bash]gem uninstall mysql2[/bash]

Then I went back to being my other user ran bundle update

[bash]bundle update rake[/bash]

Then everything was working fine.

Related: Keeping Your Hosted Ubuntu Web Server Software Up to Date – Adding a Key to Your Server for SSH Login – Checklist: Setting Up a New Domain on VPS

Using Git and Github

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To download a repository hosted on github
[bash]git clone [email protected]:account_name/repo_name.git[/bash]

The [email protected]:account_name/repo_name.git will be shown on the home page for the repository on github.com

To update your code from the master branch of the repo:

[bash]git pull origin master[/bash]

To commit the changes you have made locally:

[bash]git commit -m "the message explaining what these code changes did"[/bash]

To send your changes to the repo at github:
[bash]git push origin master[/bash]

Phusion Passenger Tips and Troubleshooting Ideas

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Some tips and troubleshooting ideas for Phusion Passenger

Phusion Passenger manages resources for rails applications – spawning new instances as needed, etc..

  • [bash]passenger-status[/bash] – provide the status of passenger rails processes

Configuring Phusion Passenger

Add lines to /etc/apache2/apache2.conf to change the default settings

  • [bash]PassengerMaxPoolSize 10[/bash] – maximum number of total rails application instances, the default is 6
  • PassengerMaxInstancesPerApp 5 – sets the maximum pool size for any 1 rails application to 10 instances (default is no limit).
  • [bash]PassengerUseGlobalQueue ON[/bash] – sets globaly queing on, it is off by default. You want globaly queuing on if your requests have large differences in response times (slow and fast responses).

Related: Passenger documentation

Troubleshooting

If you try [bash]sudo passenger-status[/bash] and get something like
*** ERROR: Cannot query status for Passenger instance 2280:
Connection refused – /tmp/passenger.2280/info/status.socket
Restarting (not reloading) apache [bash]sudo /etc/init.d/apache2 restart[/bash] may fix the problem.

Adding a Model in Ruby on Rails

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for Rails 2.*
Not for Rails 3

How to add a model in rails

  • ./script/generate resource MODELNAME

    • [ruby]./script/generate resource article[/ruby]

  • edit migrate file
  • edit model.rb – to add associations and validations
  • edit controller.rb – add the 7 rest methods
  • rake db:migrate – to run the new migration
  • If you have to add a table (like a join table) you can do something like, for example

    • [ruby]./script/generate migration add_join_table_for_articles_and_authors[/ruby]

Update to the routes file should be taken care of by generate resource, but might want to check).