Command Center

The number of inodes represents the number of files/folders you have on your web hosting account. The more inodes your account uses, the more system resources it consumes.



Thus it is wise to keep the number of your inodes(files/folders) as small as possible.

SiteGround customers can see the number of inodes they are using from their cPanel > Inodes Usage.



To reduce the number of inodes your account uses, you should:

• remove all files/folders you don't need;

• check the number of cache files you have; applications such as Joomla can generate a lot of cache files; you should regularly check your cache folder and reduce the number of cached files you keep;

• if you have Default Address (catch-all) enabled, make sure you check the mailbox regularly and delete all mails you don't need;

• check  your cPanel's main email account regularly; the mails for it are kept in:

         /home/username/mail/cur

         /home/username/mail/new     

        where username is your cPanel username. You can manually delete the messages in these folders using cPanel's File Manager or your favorite FTP  client;

• you should also check your email accounts regularly and delete any spam messages from them;

• if you have email accounts you don't need or use, it would be best to remove them;

If you have a large number of files/folders and reducing their number is not a suitable option for you, you may consider upgrading your account to a dedicated solution. There the number of inodes you use will not be a problem because all system resources will be dedicated to your account.

REFERENCES

http://kb.siteground.com/article/How_to_reduce_the_number_of_inodes_my_account_uses.html

• As an absolute value
  
  
• As a relative value.

Absolute values have a fixed, specific value. They let you, the page creator, be exact in your measurements and control the display of your Web pages.

Example: The font size might be 14 point.

When you are using absolute values always remember that the reader might be viewing your page in a different environment from what you expect.

Relative values have no fixed, specific value. Rather, they are calculated in comparison to a current value.

Example: Type size might be larger, smaller, bolder, or lighter. Indent might be specified in em spaces, which vary with the display size of the text.

Because Web pages are viewed in so many different ways, it is often a good idea to use relative values. It gives you less absolute control but it often creates a better experience for your readers and lets your page flow dynamically.

Absolute Measurement

1. Find.. to which IP address in the server is targeted by the ddos attack

netstat -plan  | grep  :80 | awk ‘{print $4}’ | cut -d: -f1 |sort |uniq -c

2. Find… from which IPs, the attack is coming

netstat -plan  | grep  :80 | awk ‘{print $5}’ | cut -d: -f1 |sort |uniq -c

In csf:

vi /etc/csf/csf.conf

SYNFLOOD

SYNFLOOD is disabled by default. If you are not receiving any sort of attack, there is no need to enable it. If you are expecting an attack, enable it and set the rules a bit strict, like

SYNFLOOD = “1″

SYNFLOOD_RATE = “30/s”

SYNFLOOD_BURST = “10″

i.e. if 30 connections are received from an IP/sec for 10 times, block it. Make sure don’t keep it too strict if you are not receiving an attack else it will generate false positives and will block legit connections.

PORTFLOOD

PORTFLOOD = 80;tcp;100;5,22;tcp;5;300

ie, If an IP makes 100 connections in 5 sec to port 80 (tcp), then it will be blocked from the server and if 5 connections in 300 sec to 22 port.

In /etc/sysctl.conf

Paste the following into the file, you can overwrite the current information.

#Kernel sysctl configuration file for Red Hat Linux

#

# For binary values, 0 is disabled, 1 is enabled. See sysctl(8) and

# sysctl.conf(5) for more details.

# Disables packet forwarding

net.ipv4.ip_forward=0

# Disables IP source routing

net.ipv4.conf.all.accept_source_route = 0

net.ipv4.conf.lo.accept_source_route = 0

net.ipv4.conf.eth0.accept_source_route = 0

net.ipv4.conf.default.accept_source_route = 0

# Enable IP spoofing protection, turn on source route verification

net.ipv4.conf.all.rp_filter = 1

net.ipv4.conf.lo.rp_filter = 1

net.ipv4.conf.eth0.rp_filter = 1

net.ipv4.conf.default.rp_filter = 1

# Disable ICMP Redirect Acceptance

net.ipv4.conf.all.accept_redirects = 0

net.ipv4.conf.lo.accept_redirects = 0

net.ipv4.conf.eth0.accept_redirects = 0

net.ipv4.conf.default.accept_redirects = 0

# Enable Log Spoofed Packets, Source Routed Packets, Redirect Packets

net.ipv4.conf.all.log_martians = 0

net.ipv4.conf.lo.log_martians = 0

net.ipv4.conf.eth0.log_martians = 0

# Disables IP source routing

net.ipv4.conf.all.accept_source_route = 0

net.ipv4.conf.lo.accept_source_route = 0

net.ipv4.conf.eth0.accept_source_route = 0

net.ipv4.conf.default.accept_source_route = 0

# Enable IP spoofing protection, turn on source route verification

net.ipv4.conf.all.rp_filter = 1

net.ipv4.conf.lo.rp_filter = 1

net.ipv4.conf.eth0.rp_filter = 1

net.ipv4.conf.default.rp_filter = 1

# Disable ICMP Redirect Acceptance

net.ipv4.conf.all.accept_redirects = 0

net.ipv4.conf.lo.accept_redirects = 0

net.ipv4.conf.eth0.accept_redirects = 0

net.ipv4.conf.default.accept_redirects = 0

# Disables the magic-sysrq key

kernel.sysrq = 0

# Decrease the time default value for tcp_fin_timeout connection

net.ipv4.tcp_fin_timeout = 15

# Decrease the time default value for tcp_keepalive_time connection

net.ipv4.tcp_keepalive_time = 1800

# Turn off the tcp_window_scaling

net.ipv4.tcp_window_scaling = 0

# Turn off the tcp_sack

net.ipv4.tcp_sack = 0

# Turn off the tcp_timestamps

net.ipv4.tcp_timestamps = 0

# Enable TCP SYN Cookie Protection

net.ipv4.tcp_syncookies = 1

# Enable ignoring broadcasts request

net.ipv4.icmp_echo_ignore_broadcasts = 1

# Enable bad error message Protection

net.ipv4.icmp_ignore_bogus_error_responses = 1

# Log Spoofed Packets, Source Routed Packets, Redirect Packets

net.ipv4.conf.all.log_martians = 1

# Increases the size of the socket queue (effectively, q0).

net.ipv4.tcp_max_syn_backlog = 1024

# Increase the tcp-time-wait buckets pool size

net.ipv4.tcp_max_tw_buckets = 1440000

# Allowed local port range

net.ipv4.ip_local_port_range = 16384 65536

Run /sbin/sysctl -p and sysctl -w net.ipv4.route.flush=1 to enable the changes without a reboot.

TCP Syncookies

echo 1 > /proc/sys/net/ipv4/tcp_syncookies

Some IPTABLES Rules:

iptables -A INPUT -p tcp –syn -m limit –limit 1/s –limit-burst 3 -j RETURN

All files accessible in a Linux (and UNIX) system are arranged in one big tree, the file hierarchy, rooted at /. These files can be spread out over several devices. The mount command serves to attach the file system found on some device to the big file tree.

Use the mount command to mount remote windows partition or windows share under Linux as follows:

Procedure to mount remote windows partition (NAS share)

1) Make sure you have following information:

==> Windows username and password to access share name

==> Sharename (such as //server/share) or IP address

==> root level access on Linux

2) Login to Linux as a root user (or use su command)

3) Create the required mount point:

# mkdir -p /mnt/ntserver

4) Use the mount command as follows:

# mount -t cifs //ntserver/download -o username=vivek,password=myPassword /mnt/ntserver

Use following command if you are using Old version such as RHEL <=4 or Debian <= 3:

# mount -t smbfs -o username=vivek,password=D1W4x9sw //ntserver/download /mnt/ntserver

5) Access Windows 2003/2000/NT share using cd and ls command:

# cd /mnt/ntserver; ls -l

Where,

• -t smbfs : File system type to be mount (outdated, use cifs)
• -t cifs : File system type to be mount
• -o : are options passed to mount command, in this example I had passed two options. First argument is password (vivek) and second argument is password to connect remote windows box
• //ntserver/download : Windows 2000/NT share name
• /mnt/ntserver Linux mount point (to access share after mounting)

Configure a system to automount a Samba share with /etc/fstab

As explained earlier you can use the mount command to mount a remote windows partition or a windows share under Linux.

/etc/fstab file contains static information about the filesystems. The file fstab contains descriptive information about the various file systems. fstab is only read by programs, and not written; it is the duty of the system administrator to properly create and maintain this file.

To mount a Samba share to be mounted when a Linux system comes up after reboot edit the /etc/fstab file and put entry as follows for your Windows/Samba share:

//ntserver/share /mnt/samba smbfs username=username,password=password 0 0

For example, if you want to mount a share called //ntserver/docs then you need to write following entry in /etc/fstab file://ntserver/docs /mnt/samba smbfs username=docsadm,password=D1Y4x9sw 0 0Where,

• //ntserver/docs: Windows 2003/NT/Samba share name
• /mnt/samba: Local mount point (you may need to create this directory first)
• smbfs: File system type (samba file system)
• username=docsadm,password=D1Y4×9sw: Share username and password

Open file /etc/fstab using vi text editor:# vi /etc/fstabAppend line //ntserver/docs /mnt/samba smbfs username=docsadm,password=D1Y4×9sw 0 0, at the end your file should read as follows:

proc            /proc           proc    defaults        0       0
/dev/hdb1       /               ext3    defaults,errors=remount-ro 0       1
/dev/hdb2       none            swap    sw              0       0
/dev/hdc        /media/cdrom0   iso9660 ro,user,noauto  0       0
//ntserver/docs /mnt/samba      smbfs   username=docsadm,password=D1Y4x9sw 0 0

Replace sharename, username and password with your actual parameters.

REFERENCES

http://longvnit.com/blog/?p=1072

Problem Statement:

A distributed caching system such as memcached is really a life-saver when it comes to reducing a great deal of READ (SELECT) traffic from MySQL tables that are in-frequently changed. However, memcached can be a object cache for anything. Using a simple key/value (get/set) API you can store anything you want limited by size constraints. Here we will show you how to install memcached from the source distribution and use it in your PHP-based (yup we are a PHP-shop) Web applications.

Step 1: Installing memcached pre-requisites

You will need to install libevent and its development pacakges via yum as follows:

 yum -y install libevent libevent-devel

Step 2: Compiling and installing memcached

Follow the steps below;

1. Download the memcached source code from: http://www.danga.com/memcached/
2. Extract the source in /usr/local/src and you should have a new sub directory [memcached-version]
3. For a default setup, run ./configure from the newly created memcached source sub directory
4. If configure runs without error, you have all the required pre-requisites and good to go to the next step. Otherwise, you need to
   
   review the errors and install any pre-requisite library and related header files via yum.
5. Now run: make and make test and make install in this order as your success continues

Now you have memcached compiled and installed.

Step 3: Setting up memcached to start when you restart your server

Make the following decisions:

1. First, decide how much memory you want to give memcached to use for caching.
2. Then decide if you want to run memcached on the default port (11211) or not.
3. Next decide if you want memcached to listen to a specific IP address if you have multiple IP addresses on your server
4. Finally decide, what user you want to run memcached as; typically, you want to run it using Apache user so that Apache processes can access memcache data

Say, you decide to use 1GB of RAM for caching and want to run memcached as user ‘httpd’ on default port. In such a case you would run the following command as root:

/usr/local/bin/memcached -d -m 1024 -u httpd

This will start memcached as a daemon process and allocate 1GB of RAM (1024MB) using default port.

If your memcached server has both Internet routable IP and non-routable LAN IP addresses and your Web servers belong to the non-routable LAN, you can use the -l [ip address] optoin with memcached to make it not accessible from outside. For example:

/usr/local/bin/memcached -d -m 1024 -u httpd -l 192.168.1.100

This tells memcacehd to listen only to 192.168.1.100 interface on the server and thus requests from the Internet will not be possible, which makes it more secure. Of course, if your Web server and memcached is running on the same server, you can use the loopback interface (127.0.0.1) to limit memcached expouser to applications running on the local Web server.

Once you know what options you need to use with memcached, you should add the command-line you use to start memcached in /etc/rc.local. This will make sure memcached starts automatically when you restart your server.

#!/bin/sh<br />echo "# Start memcached" >> /etc/rc.local<br />echo "/usr/local/bin/memcached -d -m 1024 -u httpd -l 192.168.1.100" >> /etc/rc.local

The above shell script will put a memcached command in the /etc/rc.local file so that it starts automatically with 1GB of RAM as ‘httpd’ user on a LAN interface.

Step 4: Setting up PHP support for memcached

Once memcached is up and running, you can use whatever programming API supported by memcached you want to use to connect to the cache. Since we are PHP shop, we will use PHP API. To get PHP configured for memcached, simply run the following command as root:

pecl install memcache

This will compile and install a memcached dynamically loadable module for PHP. Your next step is to edit the php.ini (use locate php.ini to locate the one that you are using; default: /usr/local/lib/php.ini) file

and add the following lines at the very end:

; start memcached<br />extension=memcache.so

Save the changes and restart Apache server. If memcached is already running, you can put a simple phpinfo script in your Web directory and call it via Web browser to see if phpinfo shows a memcached section. Such as script is shown below:

#!/bin/sh<br />echo "# Start memcached" >> /etc/rc.local<br />echo "/usr/local/bin/memcached -d -m 1024 -u httpd -l 192.168.1.100" >> /etc/rc.local

A sample output of the above script is shown below in Figure 1:



Figure 1: memcached info reported by phpinfo

Step 5: Testing memcached with a simple PHP scripts

To really know that your memcached setup is working as expected, you can use the following simple PHP scripts.

• Download read_memcache.php
• Download init_memcache.php

If you use these scripts to test your memcached setup, make sure you change the

values for MEMCACHED_SERVER amd MEMCACHED_PORT if you are running

the memcached on a different server than localhost and/or on a different port than the default one.

The init_memcached.php script sets a key/value pair in memcache and the read_memcached.php reads

the value using the same key. By setting the key and value using a script and reading it using another,

you know you are able to use a shared cache as expected.

Here is a sample run of the scripts:

$ php init_memcache.php<br />FavoriteBook is set to Childhood's End in memcached.<br /><br />$ php read_memcache.php<br />Got FavoriteBook value: Childhood's End