Archive for March, 2013

Yum: prevent a updating the packages

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When you are running the new servers, the one thing you do not want to do – is upgrade the kernel. Because that is the only Linux update operation that requires a reboot once it is done — and in a production environment you often can’t have downtime.

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Written by spectre

March 30th, 2013 at 8:05 am

Setup Oracle Java jre 1.7 on Centos 6.(1,2,3,4…)

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Download the rpm file from Install using the rpm command:

rpm -Uvh jre-7u17-linux-x64.rpm

Use alternatives to config:

[root@localhost ~]# alternatives --config java
There are 2 programs which provide 'java'.
  Selection    Command
*  1           /usr/java/latest/jre/bin/java
 + 2           /usr/java/jre1.7.0_17/bin/java
Enter to keep the current selection[+], or type selection number:

Select the java you want to use in my case 2. Test using:

[root@localhost ~]# java -version
java version "1.7.0_17"
Java(TM) SE Runtime Environment (build 1.7.0_17-b02)
Java HotSpot(TM) 64-Bit Server VM (build 23.7-b01, mixed mode)
[root@localhost ~]# 

Create links in the Mozilla Plugins directory:

[root@localhost ~]# cd /usr/lib64/mozilla/plugins/
[root@localhost ~]# ln -fs /usr/java/latest/lib/amd64/ 

Written by spectre

March 29th, 2013 at 7:21 am

Posted in Java,Tips and Tricks

Fedora, RHEL / Centos set default gateway

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There is no specific command on CentOS to set the default route or gateway, there are several ways to do this on CentOS (as there often are). The method I am showing you will work on all versions of CentOS with or without a GUI and involves directly editing the network configuration file using Vim.

Setting default gateway on CentOS first requires us to open /etc/sysconfig/network config file using Vim:

$ vim /etc/sysconfig/network

You now need to add your default GW, if you don’t know the IP of your default GW (aka default route) then you need to ask your ISP / web host or network admin. The example below assumes our default GW is


I always append this information to the bottom on the network config file on CentOS.

After adding the default route (GW) you need to restart the networking service using:

# service networking restart

Written by spectre

March 28th, 2013 at 9:21 pm

How to detect which the virtualization system on your hosting.

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Frequently, customers want to install software in a virtual machine. This can be OK, but frequently they hit a CPU,memory, or IO limit caused by running in a constrained virtual environment.When this happens, we really like to know if they’re running under virtualization when we try to support them. Here’s some tricks to detect, from
a shell, if the system is virtualized.

The first thing to check is dmesg. On a recently-booted system, checking the
‘dmesg’ command output may be sufficient. Otherwise, try “cat /var/log/dmesg”
instead of “dmesg”

Written by spectre

March 13th, 2013 at 5:59 pm

Posted in Hostings ...