linux

How to bind a range of IP’s in Redhat based linux

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How to bind a range of IP’s in Linux
This method is used by Redhat Linux based servers (Centos/RedhatEnterprise/FedoraCore).

Create a file called /etc/sysconfig/network-scripts/ifcfg-eth0-range0
And in the file place these 3 lines but change the IP’s to match YOUR assigned range.

## Start

IPADDR_START=67.18.xxx.xxx
IPADDR_END=67.18.xxx.xxx
CLONENUM_START=0

# Example | IPADDR_START=67.18.333.440
# Example | IPADDR_END=67.18.333.444
# Example | CLONENUM_START=0

## END

The CLONENUM_START should be the number at which the alias interfaces should start. If you add your 5 IP’s to this server and then want to bind a second set of IP’s you create a second file named ‘ifcfg-eth0-range1’ and change the CLONENUM_START to match the last interface alias. IE ‘eth0:5’ = CLONENUM_START=5

After you have created the above file execute the command ‘service network restart’ and your IP’s will be all setup.

*CPANEL NOTE*
Please do not use this method of binding additional IPs if you are using Cpanel. Bind the IPs through the Cpanel interface.

Linux Memory Management

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Scenario: Customer is concerned that only 100MB of their 2GB of memory is as unused or free when running the free command. However, no processes appear to be consuming large amounts of memory, and the server is not running slow.

Cause: This is not a problem, but rather a result of the way linux manages its memory. On boot linux will typically display a large amount of free memory, as no processes have started to address it yet. Once processes run, Linux will cache that memory so it is quickly addressed for the next session. What this means is that on *most* linux distros, you’ll notice that a very small amount of memory is free, even though the machine is having no problems processing data (unlike, for instance a Windows server that would be quite slow with 150K of “free” memory). The best way to judge if the server is running low on memory, is if the swap space is being addressed. If the swap is occasionally hit, using a very small amount of memory, there is no cause for concern as that space will still be addressed. However, if a large amount of swap space is being used (50% or more) then the client may want to consider a memory upgrade.

Basically, the free memory isn’t the amount of memory that is not doing something, it’s the sum total of LowMem and HiMem that he kernel has left to address.

How to add GD support to PHP on a Linux server with Plesk

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Adding GD graphic libraries support to php on your linux server with Plesk is relatively simple.

First, log into your server using ssh to get to a command line prompt.

Second, type the following command to install a version of php with GD support:

up2date php-gd

Third, restart your web service with this command:

service httpd restart

That is it. Your web server is now runing php with GD.

How do I retrieve the Plesk control panel password?

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You can always get the Plesk password if you have Administrative access to the server. If you have also lost administrative access to the server, refer to [How do I reset the password on my server]

For Windows,

1. From the Start menu, select Run.
2. Enter the following command:
“C:\Program Files\SWsoft\Plesk\admin\bin\plesksrvclient.exe” -get

For Linux,
1. Via SSH, run the following command:
cat /etc/psa/.psa.shadow

Rootkit help

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RootKit — Spyware and Junkware detection and removal tool

Go to Rootkit Hunter homepage, and download the latest release. http://www.rootkit.nl/projects/rootkit_hunter.html

## Get the latest source and untar
# cd /usr/src/utils
# wget http://downloads.rootkit.nl/rkhunter-<version>.tar.gz
# tar xfz rkhunter-*.gz
# cd rkhunter
# ./installer.sh
## run rkhunter
# rkhunter -c
Setup automatic protection on System Reboot
## Edit /etc/rc.d/rc.local
##      (or similar file depending on Linux version)
## Add the following lines at the bottom of the file

/usr/local/sbin/apf –start
/usr/local/ddos/ddos.sh -c

Formatting and Mounting a new drive in Linux

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I have installed a new slave hard drive. How do I format it and mount it?

Solution:

1. Login as root: and type the following command:

[root@34 root]# fdisk /dev/hdc

2. This screen will appear:

The number of cylinders for this disk is set to 10011.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)

3. Press p for print, this will show you the current partitons on the drive:

Command (m for help): p

Disk /dev/hdc: 82.3 GB, 82348277760 bytes
255 heads, 63 sectors/track, 10011 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System

4. There are no current partitions, if there were, press d to delete them. Then press n to create a new partition and follow the rest of the commands:

Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-10011, default 1): Enter
Using default value 1: Enter
Last cylinder or +size or +sizeM or +sizeK (1-10011, default 10011): Enter
Using default value 10011

5: Write your new partiton to the drive:

Command (m for help): w
The partition table has been altered!

—————————————

6. Now to make the file system.

[root@34 root]# mkfs.ext3 /dev/hdc1
mke2fs 1.32 (09-Nov-2002)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
10059776 inodes, 20103331 blocks
1005166 blocks (5.00%) reserved for the super user
First data block=0
614 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424

—————————————–

7. Now to make a directory to mount the new drive to.

[root@34 root]# mkdir /backups
[root@34 root]# mount /dev/hdc1 /backups
[root@34 root]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/hda3 75G 1.3G 70G 2% /
/dev/hda1 99M 14M 81M 15% /boot
none 243M 0 243M 0% /dev/shm
/dev/hdc1 76G 33M 72G 1% /backups

You will see that the new drive is labled /dev/hdc1 and is mounted to /backups.
——————————————-

8. Now edit the /etc/fstab so that the mount is there after a reboot.

Current fstab is shown below:

LABEL=/ / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/hda2 swap swap defaults 0 0

9. Now we are going to add one line at the end:

[root@34 root]# vi /etc/fstab
LABEL=/ / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/hda2 swap swap defaults 0 0
/dev/hdc1 /backups ext3 defaults 0 0

Save and quit vi.

rndc: the key is invalid

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Problem:

———
Issue:
———
While starting named, or when running /etc/rc.d/init.d/named status, you get the following error:
rndc: connection to remote host closed This may indicate that the remote server is using an older version of the command protocol, this host is not authorized to connect, or the key is invalid.

Solution:

——-
Fix:
——-

Run rndc-confgen.
running rndc-confgen would ouput something like this:
# Start of rndc.conf
key “rndc-key” {
algorithm hmac-md5;
secret “lYzcmf255w8BC6PHTSYCQA==”;
};

options {
default-key “rndc-key”;
default-server 127.0.0.1;
default-port 953;
};
# End of rndc.conf

# Use with the following in named.conf, adjusting the allow list as needed:
# key “rndc-key” {
# algorithm hmac-md5;
# secret “lYzcmf255w8BC6PHTSYCQA==”;
# };
#
# controls {
# inet 127.0.0.1 port 953
# allow { 127.0.0.1; } keys { “rndc-key”; };
# };
# End of named.conf

do as mentioned in the output, that is, copy the rndc.conf part to /etc/rndc.conf (of course, remove all the existing entries)
in /etc/named.conf, remove the existing key and controls section, and paste the one from the output of rndc-confgen.
restart named (/etc/rc.d/init.d/named restart).
This fixes the issue