Category Archives: Server Administration

Solving “502 Bad Gateway” with nginx & php-fpm

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After upgrading php-fpm, my PHP-based sites were returning “502 Bad Gateway” errors. Here’s how I managed to solve it.

Check to make sure that php-fpm is running with ps auxww | grep php – if you can’t see any php-fpm processes in the output, then you may need to re-install php-fpm. If php-fpm is running okay, then skip this first step.

sudo apt-get remove php5 php5-cgi php5-fpm
sudo apt-get install php5 php5-cgi php5-fpm

The thing to notice here is that the order in which you install the packages is important. In the past I have found that installing them in the wrong order causes the packages to be configured incorrectly.

Next, get php-fpm to listen on the correct host/port. In /etc/php5/fpm/pool.d/www.conf change the following line from:

listen = /var/run/php5-fpm.sock

To:

listen = 127.0.0.1:9000

Restart php-fpm with sudo /etc/init.d/php-fpm restart and everything should work normally again.

Automatic MySQL Backups

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It’s really easy to set up automatic MySQL backups using mysqldump. First, you need to set up a user with SELECT and LOCK TABLES privileges. In this example the user doesn’t have a password.

CREATE USER 'autobackup'@'localhost';
GRANT SELECT, LOCK TABLES ON *.* TO 'autobackup'@'localhost';

Next create the cron job with crontab -e. This job is set to run every day at 5:20am.

20 5 * * * mysqldump --user=autobackup dbname | gzip -c > /var/backups/dbname-`/bin/date +\%Y\%m\%d`.sql.gz

Don’t forget to change dbname to the name of the database that you want to backup. And that’s it – you’re done! This cron job will create a backup of your database and save it to /var/backups with a filename based on the current date, e.g. /var/backups/dbname-20120503.sql.gz

Recursively chmod Directories Only

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The find utility’s -exec flag makes it very easy to recursively perform operations on specific files or directories.

find . -type d -exec chmod 755 {} \;

This command finds all directories (starting at ‘dot’ – the current directory) and sets their permissions to 755 (rwxr-xr-x).

find . -type f -exec chmod 644 {} \;

Similarly, this command finds all files and sets their permissions to 644 (rw-r–r–).

 

Thanks to moveabletripe for the info.

Dynamic Virtual Hosts Using .htaccess

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There are several ways to set up virtual hosts on your web server. One of the more common methods is to manually create a <VirtualHost> record for each virtual host. While using this method is fine, it can end you up with a huge configuration file that is difficult to manage.

Because all of my virtual hosts are sub-directories of my web server’s base directory, I prefer to dynamically allocate the virtual host directory based on the host name. For example, I want wildlyinaccurate.localhost to point to /var/www/wildlyinaccurate. This can be achieved by modifying the .htaccess file of your web server’s base directory: Continue reading →