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Changing the SSH Port

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Sometimes you don’t want SSH running on standard port 22. Here are the steps to change it:

It’s VERY important that you leave port 22 open while you are testing the new port, otherwise you may lock yourself out of the server!
SSH into the server normally…

cp /etc/ssh/sshd_config /etc/ssh/sshd_config.root

In the /etc/ssh/sshd_config.root file that you just made, specify a new port number with the Port line:

Port 9670
#Protocol 2,1
#ListenAddress 0.0.0.0
#ListenAddress ::

Also, make sure that PermitRootLogin is set to yes or commented out.
Now open /etc/init.d/sshd and locate this section:

# Some functions to make the below more readable
KEYGEN=/usr/bin/ssh-keygen

Directly below that, add this line:

OPTIONS=”-f /etc/ssh/sshd_config.root”

Now locate this line:

initlog -c “$SSHD $OPTIONS” && success || failure

Directly ABOVE that add this line:

initlog -c “$SSHD” && success || failure

Now you need to restart sshd (service sshd restart). Before shutting down port 22, make sure that whatever port you created for ssh is either opened in the firewall or has the appropriate IPs added. Make sure to test this in a separate ssh window to make sure you can log in!

Once you’ve verified that you can log in through the new port, you have a couple options for port 22.

  • Close it altogether or just open it for specific IPs as usual
  • Disable root logins through port 22 (preferred)

To disable root logins, open the original /etc/ssh/sshd_config file and uncomment out PermitRootLogin and set to No. This will essentially allow someone to log in as the user, but not root. You didn’t really change the SSH port, you’re just running a copy of it on another port and making port 22 useless.

If you want to disable port 22 altogether, you can just directly edit the /etc/ssh/sshd_config file and restart SSHD, but you only have one chance to get it right.

Once the port is changed you would ssh into the server with the command ssh -p 9670 root@server with 9670 being the port you chose for ssh.

Closing Open Nameservers – DNS recursion

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Open nameservers allow anyone in the world to perform queries on them, which can often lead to DOS attacks and slower performance. Some system administrators prefer to have their nameservers restricted to only trust parties. To do this kind of setup, you will need to configure your named configuration:
On command line:

pico /etc/named.conf

Look for this line at the top:

include “/etc/rndc.key”;

Now add this right below it:

acl “trusted” {
205.134.252.71;66.117.3.128;127.0.0.1;
};

The IPs should be those of the nameservers…you can add other trusted IPs as well.

Now in the options section right below that, add these lines:

allow-recursion { trusted; };
allow-notify { trusted; };
allow-transfer { trusted; };

So your options section will look like this:

options {
directory “/var/named”;
dump-file “/var/named/data/cache_dump.db”;
statistics-file “/var/named/data/named_stats.txt”;
/*
* If there is a firewall between you and nameservers you want
* to talk to, you might need to uncomment the query-source
* directive below. Previous versions of BIND always asked
* questions using port 53, but BIND 8.1 uses an unprivileged
* port by default.
*/
// query-source address * port 53;
allow-recursion { trusted; };
allow-notify { trusted; };
allow-transfer { trusted; };
};

Restart named

/etc/init.d/named restart

Now you can check a service like DNSreport to make sure the changes took.

Useful MySQL Commands

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These command assume you are running a cPanel MySQL installation and logged into the server as a root user where you can do a mysql -u root without having to specify a password.
Import a database:

mysql -u root db_name < file.sql

Dump a Database (with special characters):

mysqldump -Q –add-drop-table db_name > file.sql

Dump a Database, 4.0 compatible:

mysqldump –compatible=mysql40 –add-drop-table –quote-name db_name > file.sql

Dump Multiple Databases:

mysqldump -Q –add-drop-table –databases db_name1 db_name2 > file.sql

Restore Multiple Databases (must be done as root):

mysql -u root < file.sql

Log into MySQL prompt as the user (or root):

mysql -u username -p

Show Databases: (will only show databases the user has access to. Root has all.)

show databases;

Drop a whole database:

drop database user_databasename;

Create a database: *only a root mysql user can use this command

create database user_newdb;

Select a database to work on:

use user_testdb;

Drop a specific table:

drop table table_name;

Show all MySQL Processes:

show full processlist;

MySQL Root Login Failure

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When trying to log into the MySQL shell as root you get an access denied error. To fix:

Add this line to /etc/my.cnf and restart MySQL:

skip-grant-tables

Follow these steps to reset the MySQL root password:

mysql -u root

mysql> FLUSH PRIVILEGES;
mysql> GRANT ALL PRIVILEGES ON *.* TO root@localhost IDENTIFIED BY ‘password’ WITH GRANT OPTION;
mysql> FLUSH PRIVILEGES;
mysql> exit;

service mysql restart

Remove the line you added to my.cnf and restart MySQL again.

Now go into WHM and reset the MySQL root password again. This is is necessary in order to build an association with cPanel and phpmyadmin, as well as the root user on the server to MySQL (meaning, when logged in as root to the server, you don’t have to specify a mysql root password to log in).

Missing MySQL Socket (mysql.sock) Error

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If you get some variation of the error below:

error: ‘Can’t connect to local MySQL server through socket ‘/var/lib/mysql/mysql.sock’

You need to recreate the MySQL socket symlink in /tmp:

ln -s /var/lib/mysql/mysql.sock /tmp/

If you have magically disappearing mysql.sock file, it could point to a memory issue or disk space issue on the /tmp partition.

Missing libmysqlclient.so.14 Error

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This is a common error when dealing with command line software that uses MySQL:

error while loading shared libraries: libmysqlclient.so.14: cannot open shared object file: No such file or directory

Usually this simple command will correct the problem:

cp /usr/lib/mysql/libmysqlclient.so.14 /usr/lib

Quick PEAR Usage Tutorial

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To find out what packages are installed, you can run a list:

pear list-all

To update the PEAR repositories:

pear channel-update pear.php.net

To install a package, for instance, XML_RPC:

pear download XML_RPC
pear install XML_RPC

Note on installations: you don’t always have to download the module first, but, on dedicated server environments where /tmp is mounted noexec, you may need to download the module first and then move the archive into another directory and install it manually.

If you don’t know the specific name of a PEAR module you want to install, you can search for it:

pear search <name>

To show your PEAR configuration variables:

pear config-show

To change variables:

pear config-set variable_name <value>

Install Ruby on Rails with cPanel

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Packaged in with cPanel 11 is a new Ruby installer that will seamlessly install and integrate Ruby in your system and cPanel.  To install, simple run this command:

/scripts/installruby

Once this is installed, you can test that it is functional by running:

ruby -v

If you’re more old-fashioned or are running a version of cPanel that does not have the installer, you can  find a manual installation tutorial here.

Installing Ruby on cPanel

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Here’s how to install Ruby on Rails on a cPanel system:

Update: These instructions were modified for Ruby 1.8.6, since 1.8.5 is no longer available!

First install Ruby:

wget ftp://ftp.ruby-lang.org/pub/ruby/1.8/ruby-1.8.6.tar.gz
tar -xvzf ruby-1.8.6.tar.gz
cd ruby-1.8.6
./configure
make
make install

Now, install the Gems and Rails:

wget http://rubyforge.org/frs/download.php/11289/rubygems-0.9.0.tgz
tar -xvzf rubygems-0.9.0.tgz
cd rubygems-0.9.0
ruby setup.rb
gem install rails

Install Fast CGI

wget fastcgi.com/dist/fcgi-2.4.0.tar.gz
tar -xvzf fcgi-2.4.0.tar.gz
cd fcgi-2.4.0
./configure
make
make install

wget fastcgi.com/dist/mod_fastcgi-2.4.2.tar.gz
tar -xvzf mod_fastcgi-2.4.2.tar.gz
cd mod_fastcgi-2.4.2
/usr/local/apache/bin/apxs -o mod_fastcgi.so -c *.c
/usr/local/apache/bin/apxs -i -a -n fastcgi mod_fastcgi.so
gem install fcgi

Edit the Apache config file and add the fcgi module:

pico /usr/local/apache/conf/httpd.conf

LoadModule fastcgi_module libexec/mod_fastcgi.so
FastCgiIpcDir /tmp/fcgi_ipc/
AddHandler fastcgi-script .fcgi
< /IfModule>

Then restart Apache

Install RMagick and GetText:

wget http://umn.dl.sourceforge.net/sourceforge/graphicsmagick/GraphicsMagick-1.1.7.tar.gz
tar -xvzf GraphicsMagick-1.1.7.tar.gz
cd GraphicsMagick-1.1.7
./configure
make
make install

Install MySQL for Ruby:

gem install mysql

Now make the test Installation. To do this, log in as your user (not root)

su user
cd ~
rails test
cd public_html
ln -s ../test/public/ rails
cd ../test/
chmod -Rf 777 tmp/
cd public
chmod 755 dispatch.fcgi
pico .htaccess

Now, find the line in the .htaccess that looks something like this:

RewriteRule ^(.*)$ dispatch.cgi [QSA,L]

And change “dispatch.cgi” to “dispatch.fcgi”

To see if you’ve installed everything properly, just browse to the Rails folder:

http://yourdomain.com/rails/

cPanel PEAR Installer Errors

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A new feature in cPanel 11/x3 is the PEAR module installer that allows users to install their own PEAR modules locally in their account.  I’ve heard that a lot of servers with existing PHP installations have had problems getting this to work, and instead are prompted with this error:

X-Powered-By: PHP/5.2.3
Content-type: text/html

Parse error: syntax error, unexpected T_STRING in /usr/local/cpanel/base/frontend/x3/module_installers/live_install.html on line 8

/usr/bin:/bin:/sbin:/usr/sbin:/usr/bin:/bin:/usr/local/bin

As far as I know there are two causes for this problem:

1.  /usr/bin/php is missing or is not compiled with PEAR or CLI.  Some servers have a CGI and CLI binary installed, so you’ll need to symlink /usr/local/bin/php to /usr/bin/php:

ln -s /usr/local/bin/php /usr/bin/php

2.  Your PHP installation is compiled without CLI support (–disable-cli), which is common when compiling PHP as a CGI binary or for suPHP.  If you have an installation with CLI enabled you will need to link that binary to /usr/bin/php, otherwise compile a second copy with the command line interface enabled.