WordPress: Multiple Blog Network on One Server – Overcoming Conflicts

I ran into a problem when I added a second WordPress blog network to my server. I had the Curious Cat Blog Network up and running for quite some time with sub-domains for each individual blog in the network. WordPress automatically dealt with routing the sub-domains and having urls work. It really is very nice how easy it is to create a new blog and have everything up and running – just add it in WordPress, no need to touch the server directly. Blog networks are a new feature in WordPress 3.0 (I think) which are very nice. I would imagine it builds on effort with Wordpres MU but it is just part of regular WordPress now.

When I added the second blog network however the new faux-sub-domain that should be used affordable-funeral.moneyite.com would instead be redirected to curiouscatnetwork.com and since no such domain existed on curiouscatnetwork.com it gave the standard error message WordPress generates for the case where a sub-domain url is not recognized.

The main domain for the new site was working: moneyite.com. I tried searching around for some solutions to this problem online but couldn’t find any. I am not sure if multiple wordpress blog networks should work on the same server without any special needs. But it wouldn’t for me. I found a solution that did work so I will share what worked for me.

I created new sites-available records for each of the sub-domains and once you reload Apache everything seems to work. I am not sure their isn’t some problem with doing things this way that I haven’t uncovered yet. But it is working for me so I wanted to share this in case it can help anyone else trying to use multiple wordpress blog networks on one server.

Related: Checklist for moving an existing WordPress site to a new web hostWordPress error: Image could not be processed. Please go back and try again

Checklist: Setting Up a New Domain on VPS

Two great hosts for Ruby on Rails are Slicehost and Linode. With these hosts you fully manager your virtual private server, installing the operating system, modifying apache (on Ning…), etc.. I use Ubuntu as the operating system and Apache as the web server.

If you are moving a domain from elsewhere it can be wise to reduce the TTL time to say 5 minutes a few days before you make the switch. This is make the change propagate across the internet more quickly.

  1. And DNS entry on your profile (login to your, for example, Linode account)
  2. Add a new file for /etc/apache2/sites-available/your_site_name.com
  3. sudo nano /etc/apache2/sites-available/example.com

    The file would look something like this: with your ip in place of 8.8.8.8

    ServerAdmin is the address Apache will use to send error messages to. Using gmail and the + option lets you use one gmail account and just use rules to filter all your sites.

  4. create the directories needed on your server
  5. enable the site (for apache)
    sudo a2ensite example.com
  6. You should see the file you created /etc/apache2/sites-available/example.com now also at /etc/apache2/sites-enabled/example.com

  7. Test the site out to make sure the setup is working properly. Create a index.html page and just verify the page is displayed. Change your local hosts file to point to your server IP address for the new domain you created. If not, take steps to get this to work, before continuing with the rest of the checklist.
  8. copy over the site – if you are moving the site from elsewhere
  9. remember to move the database over, if the site relies on a database
  10. restart apache
    sudo /etc/init.d/apache2 restart
  11. You can test the site out, before updating the DNS, by changing your local hosts file to point to your server IP address for the new domain you created.

    Resources: Install the Apache 2 Web Server on Ubuntu 10.04 LTS (Lucid)

Replacing a Host Key

Host keys are used to security log into remote servers (such as Virtual Private Servers – VPS). With Ubuntu if you are using host keys to sign into servers securely and have asked for strict checking, if you make a change (such as rebuilding your VPS) the host key will change and you cannot login and will get a message like:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is

Please contact your system administrator.

RSA host key for 128.0.0.128 has changed and you have requested strict checking.
Host key verification failed.

if that happens you need to remove your local host key. Then you can sign back in and you will be able to save a new copy of the host key. If you don’t know why the key has changed you should figure that out first as it maybe be an indication of an important security problem. To remove you local key, you can use ssh-keygen -R [ip address of server with the bad key] for example: ssh-keygen -R 128.0.0.128

Then when you try to sign in you will get

The authenticity of host '128.0.0.128 (128.0.0.128)' can't be established.

RSA key fingerprint is ed:...:ea.
Are you sure you want to continue connecting (yes/no)?

And if you know why (such as you made changes to the server) you can say yes and connect and save the new known host key.

Basic MySQL Performance Monitoring

Basic MySQL Performance Monitoring

regular Ubuntu cli tools

  • mysqladmin status – mysqladmin status -uroot -p

MySQL command line interface tools

mysql -uroot -p

to open the command line.

SHOW GLOBAL STATUS;
SHOW ENGINE INNODB STATUS;
SHOW PROCESSLIST;
SHOW GLOBAL STATUS LIKE 'Qcache_%';

cli tools

  • mytop – top for MySQL. Install using: sudo apt-get install mytop (assuming Ubuntu operating system). There is a very useful setting file that can be used to set parameters instead of having to include them in each command. Save the file as ~/.mytop.
  • MySQLTuner – provides suggestions on performance improvements and my.cnf settings by analyzing data on your mysql database server.

Setting considerations

  • If Open_tables (SHOW GLOBAL STATUS will show this) is equal to your
    table_cache size

    (set in /etc/mysql/my.cnf) that means it is being capped by your setting. The more MySQL has to read the table from disk the more IO and slower response, so if you have available RAM increasing the table_cache size may well make a big difference.

  • Key_reads/Key_read_request ratio should normally be < 0.01 (per MySQL manual, this means that nearly all key requests are taken from RAM). You can get both values using SHOW GLOBAL STATUS and then calculate the ratio. If the ratio is too high, consider increasing the key_buffer (in /etc/mysql/my.sql).
  • key_writes/key_writes_request should normally be near 1 (per MySQL manual)

Phusion Passenger Tips and Troubleshooting Ideas

Some tips and troubleshooting ideas for Phusion Passenger

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

  • passenger-status

    – provide the status of passenger rails processes

Configuring Phusion Passenger

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

  • PassengerMaxPoolSize 10

    – 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).
  • PassengerUseGlobalQueue ON

    – 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

sudo passenger-status

and get something like
*** ERROR: Cannot query status for Passenger instance 2280:
Connection refused – /tmp/passenger.2280/info/status.socket
Restarting (not reloading) apache

sudo /etc/init.d/apache2 restart

may fix the problem.

System Monitoring Tools for VPS

Tools for monitoring performance and troubleshooting Ubuntu VPS web servers

  • Munin – graphs of system resources over time. Very nice. Can be a bit difficult to setup.
  • top – system stats
  • iotop – like top, but for io stats. Install
    sudo apt-get install iotop

    Useful setup

    iotop -b -o -d 30 -t

    -b (batch – so you can keep a running tally of results) -o (only those processes with io) -d (delay and seconds – how often to print out stats) -t (include time in printout)

  • vmstat – stats on memory, io, swap, cpu and system. Example:
    vmstat 10

    (prints out stats every ten seconds.

  • iostat

Error logs

  • sudo nano /var/log/apache2/error.log

Apache web server access log statistics

  • Webalizer –
    sudo apt-get install webalizer

    GeoIP is required for webalizer

    sudo apt-get install geoip-bin

    detailed instructions

Linux/Ubuntu File and Directory Permissions

Linux (and therefore Ubuntu) has file permissions on each file and directory for the owner, group and everyone else. Those permissions determine if the file can be viewed, executed or edited.

Only the owner of a file or directory (or a privileged user, root for example) may change its mode.

Ownership of a file

To change the ownership of the file or directory: chown new_owner_username directory

chown john public_html

to change the ownership of directory (and all the files and folders in the directory) and also the group: chown -R new_owner_username:new_groupname directory

chown -R john:developers public_html

to change the ownership of all the files in the current directory and also the group: chown -R new_owner_username:new_groupname *

chown john:developers *

File permissions

The easiest way to set Linux file permissions is using a 3 digit sequence. The first digit designates owner permission; the second, the group permission; and the third, everyone else’s permission.

Read = 4
Write = 2
Execute = 1

The digit is the sum of those. So if you want to grant only read permission you use 4; read and execute 5; read, write and execute = 7.

chmod 775 index.html

That will set the permissions on index.html so the owner, and a user in the group specified can read, write and execute the file and everyone else can read and execute.

chmod -R 755 public_html

That will set the permissions on files and directories (recursively through all subdirectories) so the owner can read, write and execute; members of the group and everyone else can read and execute (but not write).

ls - l

That will give you a list of files and directories, in a directory, with the owner and group settings and the permissions for all 3 (those 2 and everyone else), which will look something like:

-rw-r--r-- 1 root developers   397 2008-05-25 20:33 index.html
-rw-r--r-- 1 mary developers  9177 2010-05-02 22:18 unix_file_permissions.html
...

The lines start with the permissions for the owner, group and then everyone else. There are 9 total characters, 3 for each. Taking the top line above:

rw-r--r--
rw-  (means the owner has read and write permission but not execute)
r--  (means the group has only read permission)
r--  (means everyone else has only read permission)

The next column tells you the number of hard links to the file or directory. Then column tells you the owner, then the group. Then the byte size of the file, the date it was last change and then the file name.

root
means the username of this file is named root

developers
group (means those users in the group named developers have the group permissions indicated)

Related: Ubuntu command line interface syntax examples

Checklist: Moving WordPress site to a New Host

Checklist for moving an existing WordPress site to a new web host

A checklist for moving an existing WordPress site to a new VPS web host, when you have full admin rights over the server.

  1. Set DNS TTL’s down to 5 minutes (a few days prior to the move). This will allow the nameserver update to propagate more quickly.
  2. Set up new domain on the new host (Checklist for setting up a new domain on your VPS)
  3. Install WordPress on new host
  4. Copy old content directory to new WordPress host
  5. Copy old database to new host (how to use secure copy to copy database to new server)
  6. Update wp-config on new host
  7. Enable mod_rewrite in Apache on the new server. From the command line:
  8. a2enmod rewrite

  9. Restart apache
    /etc/init.d/apache2 restart

  10. Test that everything works (you can change your host file to test things out easily)
  11. Update registrar to point domain to the nameservers for the new host

Related: create a new database and run .sql fileDisplay text based on if it is the WordPress blog home page

If WordPress is up to date you could also just copy over everything for steps 1 and 2. I am using this for several sites I have had for years, I figure starting with a clean install of WordPress is a good idea, but it is not necessary.