This can easily be changed via phpMyAdmin.

ssh-keygen -t dsa

Then do:

cat /root/.ssh/id_dsa.pub

Then copy over the whole thing into /root/.ssh/authorized_keys on the server you are trying to get connection.

This can be useful for setting up RSync between two servers.

To reset, get into SSH via console on your VPS web server company’s control panel.

Type:

service network stop

then

service network start

For some web servers, you might have to use:

/sbin/service network stop

and

/sbin/service network start

Wait like 5 seconds and see if you can ping the outside world:

ping google.com

If you get connected, you should be good to go.

This can save lots of time restarting a faulty network yourself instead of opening a support ticket and waiting forever.

I am still experimenting with PHP-FPM but it seems like a pretty good way to go as far as handling the PHP-CGI processes.

To do this, you will need to install EPEL & CentALT repositories:

rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/x86_64/epel-release-5-3.noarch.rpm

rpm -Uvh http://centos.alt.ru/repository/centos/5/x86_64/centalt-release-5-3.noarch.rpm

Then do:

yum install php-fpm

to install php-fpm.

Edit the file /etc/php-fpm.conf

and my suggested setting changes:

<value name=”user”>apache</value>
<value name=”group”>apache</value>

The max_children is set to 1 as default, set it to something like 50, this really is the cool part about php-fpm.

<value name=”max_children”>50</value>

PHP-FPM doesn’t allow for root user and group so I set it to apache.  You will also need to set your web directories to apache user and group by doing:

chown apache:apache /mywebdirectory

Start the PHP-FPM by doing:

/sbin/service php-fpm start

If you get some kind of session errors, simply erase all the session files where the error shows.

For CentOS, you can do:

chkconfig php-fpm on

so it will start whenever your webserver is rebooted.

If you have been using fastcgi, make sure to do:

chkconfig fastcgi off

so it doesn’t interfere.

I’ve been researching many ways to optimize large file downloads but probably the best way is to simply rate limit the bandwidth on how fast each user can download.

You can add the following line to your HTTP directive in /etc/nginx/nginx.conf:

limit_rate 100k

This will limit each user to download at maximum of 100kb/second.

You can change this number to see which one fits best for your server.

You can also add limit_rate_after clause to only limit after a portion of the file has been downloaded:

limit_rate_after 1m;
limit_rate 100k

This will limit downloads only after the first megabyte, potentially not slowing down smaller file downloads and your website.

You can do this with iptables (which is pain is the a**) or just use this:



yum install system-config-securitylevel



Then do:



/usr/bin/system-config-securitylevel-tui



And there’s a “Customize” menu where you can set WWW and SSH open.

Well, my Nginx kept crashing, actually my PHP-cgi processes started crashing after the server ran for a bit. The weird thing was, the server had no load.

Upon carefully watching my “top” status in linux for awhile, I realized there’s only one PHP-CGI process running, whereas all my other Nginx web servers ran multiple (around 5-6 at any given time).

I compared out the versions of the Spawn-cgi and realized the new Spawn-cgi I had installed only spawned one PHP-CGI process.

I decided to install an older version off Lighttpd and it fixed the problem:

wget http://www.lighttpd.net/download/lighttpd-1.4.18.tar.bz2

tar -xvjf lighttpd-1.4.18.tar.bz2

cd lighttpd-1.4.18

./configure

make

cp src/spawn-fcgi /usr/bin/spawn-fcgi

After that restart your PHP-CGI:

/sbin/service fastcgi stop

/sbin/service fastcgi start

Yey, problem solved and now Nginx server runs multiple PHP-CGI processes and no more weird crashes. Sometimes, older programs work better. Perhaps the new Spawn-cgi version has bugs?

Enter your MySQL command line with something like:

mysql -uroot -p

Then enter your password.

Once inside the MySQL command line do:

show databases;

and then find your database for the WordPress blog that you want to change password.

use mydatabase;

where mydatabase should be “your” database.

Then do:

update wp_users set user_pass =MD5(’typenewpasswordhere’) where id=1;

to change the admin password.

That’s it!

You can also do:

SELECT ID, user_login, user_pass FROM wp_users;

to list current users.

Each DNS request (every time you request from any domain name using an API) takes anywhere between 0 to 500 miliseconds. Sometimes, adding DNS caching to your web server can make your website load in 1 second versus 10 seconds.

Anyways, it’s easy to do and here’s how to do it on CentOS/Fedora linux servers: (Ubuntu should be similar, just use apt-get install of yum)

First install Bind-utils:

yum install bind-utils

Do a command:

dig yahoo.com

Do it several times and note how many miliseconds it takes to retrieve the URL. Later, after we install DNSMasq, we will try dig command again to see if your web server has started caching DNS requests.

Install DNSMasq:

yum install dnsmasq

Edit the file in /etc/dnsmasq.conf:

Then add the following lines:

listen-address=127.0.0.1

cache-size=500

Next, edit the file in /etc/dhcp6c.conf:

Then add the following line:

prepend domain-name-servers 127.0.0.1;

Next, edit the file in /etc/resolv.conf:

Add the following lines with 127.0.0.1 first:

nameserver 127.0.0.1

nameserver 208.67.220.220

nameserver 8.8.8.8

nameserver 8.8.4.4

208.67.220.220 is DNS server of Open DNS, which I highly recommend as it’s FAST.

Also 8.8.8.8 and 8.8.4.4 are DNS servers of Google, which are also FAST.

You can however, decide to use any other DNS such as your hosting company’s.

You can do a test of how fast they are by doing a ping test such as:

ping 8.8.8.8

to test Google’s DNS server response times.

Next, you can start the DNSMasq so your web server starts caching, do:

/sbin/service dnsmasq start

Also, you will want to add DNSMasq to your chkconfig list so it will start up next time your web server reboots, do:

chkconfig dnsmasq on

To check all the processes running at boot-up, do:

chkconfig –list

That’s it!

Now do a dig command on yahoo.com, you should see 0 miliseconds after the first dig command!

dig yahoo.com