Disable Recursion for DNS

Recursion allows your DNS server to contact other DNS servers to assist in resolving domain names when it cannot resolve the domain itself. While recursion can prove to be useful tool when it is necessary, it also opens the DNS server open to attack, which could take down the DNS server altogether. Recursion is generally only necessary when there is a known need for it. If recursion is not a known need for your DNS server, it is best to disable recursion. Follow the steps below based on your operating system or control panel to disable DNS recursion.

Disable Recursion in Plesk

Log into the Plesk Admin Panel.
Select Tools and Settings.
Click DNS Template Settings from the section.
Select Localnets from the DNS Recursion section.
Click the OK button.

Disable Recursion in Windows Server 2003 and 2008

Go to DNS Manager from the Start menu:

Click the Start button.
Select Administrative Tools.
Select DNS.

Now Right click on the desired DNS Server in the Console Tree.
Select the Proprerties tab.
Click the Advanced button in the Server Options section.
Select the Disable Recursion checkbox.
Click the OK button.

Disable Recursion in Linux

Locate the named.conf file within the operating system.Open the named.conf file in your preferred editor.

Add the following details to the Options section:

opttions{
.............
allow-transfer {"none";};
allow-recursion {"none";};
recursion no;
............
};

Save and exit the file. The restart the named service. 

# /etc/init.d/named restart

Weird charecters on site

If you find weird characters in your site instead of the original content as shown below, you can try the fix given below.

 K511����� �Ϸ��Ϸ�ر� ��ȥ���� 917������Ϸ��

For fixing this issue, open your " http.conf " file with your favorite editor

# vi http.conf

And find the line,

AddDefaultCharset UTF-8 

 And comment it.

#AddDefaultCharset UTF-8

Now restart apache.

# /etc/init.d/httpd restart 

Now you should be able to view the site without any weird characters.!!


  

Starting nginx: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)

While trying to start / restart nginx, if get the following error

# /etc/init.d/nginx restart
Stopping nginx: [FAILED]
Starting nginx: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] still could not bind()

Run the following command to fix the issue. 

# fuser -k 80/tcp

 Where:  fuser - identify processes using files or sockets
               -k     Kill  processes accessing the file.

Now you can start / restart nginx successfully.

# /etc/init.d/nginx restart
Stopping nginx: [ OK ]
Starting nginx: [ OK ]

!!!!!!!!!!!!!!!!................

ERROR! MySQL manager or server PID file could not be found!

Some times you may get mysql error on the page. And on checking the status of the mysql, if you are getting following error 

# /etc/init.d/mysqld status
ERROR! MySQL manager or server PID file could not be found!

Then the Fix is below.

Check the file /etc/my.conf and see any thing mentioned as " basedir= ". If nothing mentioned in the file, by default it would be /var/lib. Then, check the permission for /var/lib/mysql and make sure all are having user and group " mysql ". If not do

#chown -R mysql.mysql /var/lib/mysql

Then, restart mysql

#/etc/init.d/mysql restart

This should fix the issue.

Enable Iptables Modules for a VPS

Before enabling the modules to the VPS , make sure that its enabled in the root node of the VPS. You can check it using the command below.

#lsmod | grep -i module_name

If its not enabled, then enable it by using the modprobe command 

#modprobe iptables_module
#modprobe ipt_helper
#modprobe ipt_REDIRECT
#modprobe ipt_TCPMSS
#modprobe ipt_LOG
#modprobe ipt_TOS
#modprobe iptable_nat
#modprobe ipt_length
#modprobe ipt_tcpmss
#modprobe iptable_mangle
#modprobe ipt_tos
#modprobe iptable_filter
#modprobe ipt_helper
#modprobe ipt_tos
#modprobe ipt_ttl
#modprobe ipt_SAME
#modprobe ipt_REJECT
#modprobe ipt_helper
#modprobe ipt_owner
#modprobe ip_tables
#modprobe ipt_MASQUERADE
#modprobe ipt_multiport/xt_multiport
#modprobe ipt_state/xt_state
#modprobe ipt_limit/xt_limit
#modprobe ipt_recent
#modprobe xt_connlimit
#modprobe ipt_owner/xt_owner
#modprobe iptable_nat/ipt_DNAT
#modprobe iptable_nat/ipt_REDIRECT

Now to enable the module to the container, first stop the container which one you want to enable the module . Assuming the vps id as 101 here.  

# vzctl stop 101

Now you can enable the module to the vps either by executing the following command

# vzctl set 101 --iptables ipt_REJECT --iptables ipt_tos --iptables ipt_TOS --iptables ipt_LOG --iptables ip_conntrack --iptables ipt_limit --iptables ipt_multiport --iptables iptable_filter --iptables iptable_mangle --iptables ipt_TCPMSS --iptables ipt_tcpmss --iptables ipt_ttl --iptables ipt_length --iptables ipt_state --iptables iptable_nat --iptables ip_nat_ftp --save

                                                 OR

By adding manually to the configuration file /etc/vz/conf/veid.conf 

#vi /etc/vz/conf/101.conf

and then paste following at the end of the file.

 

IPTABLES="iptable_filter iptable_mangle ipt_limit ipt_multiport ipt_tos ipt_TOS ipt_REJECT ipt_TCPMSS ipt_tcpmss ipt_ttl ipt_LOG ipt_length ip_conntrack ip_conntrack_ftp ip_conntrack_irc ipt_conntrack ipt_state ipt_helper iptable_nat ip_nat_ftp ip_nat_irc"

Now restart the container.

# vzctl restart 101

This will enable the modules to the vps.

CSF Blocking EVERYTHING

If you have csf installed on a OpenVZ container, suddenly you may end up with  csf blocking all ips and even ssh, email and all services will not be accesible, even though server is working, but firewall puts a block on everyone, and appears offline to others.

I got this fixed by doing the following steps:

Login to the host node and edit /etc/vz/conf/vpsid.conf. For example I'm using 101 as vpsid.

[root@node ~]# vi /etc/vz/conf/101.conf

Then add the following line to the end of the file. 

IPTABLES="iptable_filter iptable_mangle ipt_limit ipt_multiport ipt_tos ipt_TOS ipt_REJECT ipt_TCPMSS ipt_tcpmss ipt_ttl ipt_LOG ipt_length ip_conntrack ip_conntrack_ftp ip_conntrack_irc ipt_conntrack ipt_state ipt_helper iptable_nat ip_nat_ftp ip_nat_irc"

Now restart the container.

[root@node ~]# vzctl restart  101

The problem should be resolved now!!

umount: /***: device is busy.

Sometimes when you try to umount a device you end up with error " umount: /***: device is busy ", 

e.g.

# umount /***

umount: /***: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))

Fix 1: It means that some process has a working directory or an open file handle underneath the mount point. The best thing to do is to end the offending process, change its working directory or close the file handle before unmounting.

Fix 2: There is an alternative on Linux though. Using umount -l calls a "lazy" unmount. The filesystem will still be mounted but you won't be able to see or use it, except for processes that are already using it. When the offending program exits (through whatever means) the system will "finish" unmounting the filesystem.

# umount -l /***

 This wil FIX it........

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)

If you end-up with the error ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2), it means 2 things.

1. You don't have permissions to access the directory /var/lib/mysql/. Check the permission there and change the ownership mysql if it is not. For that do the following

#chown -R mysql.mysql /var/lib/mysql

Then, restart mysql

#/etc/init.d/mysql restart

2. If the permissions are correct, the /tmp/mysql.sock may not be existing. If so do the following.

#/etc/init.d/mysql stop

Then touch a file mysql.sock

#touch /tmp/mysql.sock

Then start the mysql server.

#/etc/init.d/mysql start

 This should fix the issue.....

Install nginx server

Ton install nginx server login to the server as root. Then navigate to the directory whre you would like to download the source file. I usually use /usr/local/src.

#cd /usr/local/src

You can now donload the installation file as shown below.

#wget http://nginxcp.com/latest/nginxadmin.tar

Once the download is finished, extract the tar file that you have downloaded.

#tar xf nginxadmin.tar

Now get into publicnginx

#cd publicnginx

And run the command below to install. 

./nginxinstaller install

You are done !! 

bash: scp: command not found lost connection

 When you try to scp some thing to a remote server you may endup with the error as shown below.

# scp somefile 10.10.10.10:/home
root@10.10.10.10's password: 
bash: scp: command not found
lost connection

This error occurs because the remote host is missing the openssh-clients package. To fix this issue just login to the remote server, and run the command below.

#yum install openssh-clients

This will fix the issue and you could now scp without any issue.

WHM does not show the nameserver ips

When you check the nameserver ips from WHM, it wont show the ip some times. 

Main >> DNS Functions >> Nameserver IPs

To fix this, login to the server as root. The navigate to /var/cpanel.

#cd /var/cpanel

Then make a backup of the file nameserverips.yaml

#cp nameserverips.yaml nameserverips.yaml.bkp

Now edit the file using any editor.

#vi  nameserverips.yaml

It will look like as shown below:

---
ns1.yourdomain.com:
  "": 0
  count: '2'
  zones: ns1.yourdomain.com,ns2.yourdomain.com
ns2.yourdomain.com:
  "": 0
  count: '2'
  zones: ns1.yourdomain,ns2.yourdomain

Now make the following changes in the file.

---
ns1.yourdomain.com:
  "10.10.10.1": 1
  count: '2'
  zones: ns1.yourdomain.com,ns2.yourdomain.com
ns2.yourdomain.com:
  "10.10.10.2": 1
  count: '2'
  zones: ns1.yourdomain,ns2.yourdomain

Where you should replace the nameservers ns1.yourdomain.com and ns2.yourdomain.com with your nameservers, and  ips 10.10.10.1 and 10.10.10.2 to your name server ips.

How to install SSL Certificate in a server running Lighttpd

For installing SSL Certificate for domain running in Lighttpd, follow the steps bellow. 

Login to the server and download / copy the certificate files.

Once this has been done, you need to concatenate the certificate and key file into a single pem file. For this follow the step below.

#cat yourdomain-name.key yourdomain-name.crt > yourdomain-name.pem

Now you need to edit lighttpd.conf file and add the following lines.

# vi /etc/lighttpd/lighttpd.conf

     var.confdir = "/etc/lighttpd"
     $SERVER["socket"] == "10.10.10.10:443" {
     ssl.engine = "enable"
     ssl.pemfile = var.confdir + "/yourdomain-name.pem"
     ssl.ca-file = var.confdir + "/your.crt"
     server.name = "your.domain.com"
     server.document-root = "/your/document/root/" }

Make sure that the var.confdir (/etc/lighttpd) is the location where you saved your certificate files. Also change the IP address (10.10.10.10) to your IP address.

Now restart Lighttpd.

#restart lighttpd

You are done. !!!!

How to avoid " cp: overwrite " while copying

While you copy some directory or files it will prompt " cp: overwrite " as shown below.

# cp -rf /some/file/or/directory/* /another/location
cp: overwrite `./some/files/yyy'?

 If there is lot of files, it will hard to do. So to avoid this, just put "\" before the command cp

# \cp -rf /some/file/or/directory/* /another/location

This will eliminate the interactive mode.

how to change mysql password for an user

Suppose you have got a user " db_user " and you have lost the password for the user. You need to reset it. For this just follow the steps bellow.

Get into the server as root, then get into mysql as root user.

#mysql -u root -p******

Where ***** should be replaced with your password for mysql root user.

Then execute the following commands.

mysql> use mysql;

mysql> SET PASSWORD FOR 'db_user'@'localhost' = PASSWORD('new-password'); 

Query OK, 0 rows affected (0.00 sec)

mysql> FLUSH PRIVILEGES;

           Query OK, 0 rows affected (0.00 sec)

mysql>quit

Now the password will be reset to  new-password for the user db_user.

Assign dedicated ip to a domain in Cpanel

Assigning dedicated ip to an account is simple. You just need to follow the steps below.


Home » IP Functions

Home » IP Functions » Change a Site’s IP Address

From here select the account for which the ip has to be changed. Once selected click "Change" button at the bottom.

Now select the ip from the list that you click on the drop down button, and click " Change ".

This will change the ip of the account. 

!! 'httpd' is disabled via '/etc/apachedisable', please re-enable to continue. !!

You may end up with the following error while running /scripts/easyapache

!! 'httpd' is disabled via '/etc/apachedisable', please re-enable to continue. !!

To resolve this, Login to your WHM

Home » Service Configuration » Service Manager

The boxes for http would be unchecked, Just check it

Then Click the " Save " button at the bottom of the page.

Now you can run easyapache without any issue.

Missing Perl Libraries error while installing CSF on CentOs 5/6

While installing CSF you may end up with the following error. 

Checking Perl modules...
Can't locate LWP/UserAgent.pm in @INC (@INC contains: /etc/csf /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .) at (eval 22) line 2.
BEGIN failed--compilation aborted at (eval 22) line 2.

Can't locate Time/HiRes.pm in @INC (@INC contains: /etc/csf /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .) at (eval 27) line 2.
BEGIN failed--compilation aborted at (eval 27) line 2.

This have got a simple one line fix. Just do the following. 

root@amaziah [~]# yum install -y perl-libwww-perl perl-Time-HiRes

error: configure: error: APR is needed to build mod_suphp for Apache 2.x but was not found

If you are facing the following error while installing suPhp

error: configure: error: APR is needed to build mod_suphp for Apache 2.x but was not found

Run ./configure as shown below.

# ./configure --with-apr=/usr/bin/apr-1-config

This should fix the issue. Now you can proceed with

# make

# make install

How to Flush DNS

How to Flush DNS cache in Microsoft Windows

For this just to the following steps.

Start => Run => cmd

Now give the following command in the command prompt

c:\> ipconfig /flushdns 

You are Done!!


How to Flush DNS cache in a Linux Server

For this login to the server. And issue the following command.

root@amaziah [~]# /etc/init.d/nscd restart

                          OR

root@amaziah [~]# service nscd restart

                          OR

root@amaziah [~]# service nscd reload

This will flush DNS cache in Linux.

How to restrict the users accessing a directory

Suppose you have a domain example.com. In the document root of example.com you have a directory "confidential". And you don't want all people to access this directory. So to restrict the access to this directory except few ips. For example 192.168.1.1, 192.168.1.2, 192.168.1.3. Then  you need to follow the steps given below.

First create a file .htaccess  in  "confidential" directory.

root@amaziah [~]#cd /document root/confidential 

#touch .htaccess

Now edit .htaccess using your favorite editor

#vi .htaccess

 Order Deny,Allow

Deny from all

Allow from 192.168.1.1

Allow from 192.168.1.2

Allow from 192.168.1.3

 

Now your confidential data are safe. Only users from 192.168.1.1, 192.168.1.2 & 192.168.1.3 can access it. All others will be denied.  :)