Advanced ( Expert) Linux / Unix System Administrator

These tutorials assumes that you have rock solid understanding of Unix like operating systems and very comfortable with most aspects of the Unix/Linux such as networking/distributed computing environments,routing, firewalls, servers, client/server programming, and the design of consistent network-wide filesystems, load-balancers, security and much more. ( rss feed )

Recently Debian Linux version 7.0 (“Wheezy”) released. This version shipped with many new features – improvements to multimedia support, improved security through hardening flags and the OpenStack suite and the Xen Cloud Platform to name a few. How do I upgrades from Debian Linux version 6.x.x (squeeze) to the latest version 7.0.0 wheezy using command line options? How do I upgrade my Debian 6.x server to 7.x over the ssh session?

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I recently added SSD to my home server and reloaded the operating system. However, when I try to access my dm-crypt based old disk, I am getting the following error:

Reading all physical volumes. This may take a while...
WARNING: Duplicate VG name server01: Existing bc7YA8-eEXt-1aA1-OHTr-zJkA-ucd0-DsbRTc (created here) takes precedence over RIKiar-w3MG-Gzh5-VFWq-bkRT-9IFc-ia8k87
WARNING: Duplicate VG name server01: Existing bc7YA8-eEXt-1aA1-OHTr-zJkA-ucd0-DsbRTc (created here) takes precedence over RIKiar-w3MG-Gzh5-VFWq-bkRT-9IFc-ia8k87
Found volume group "server01" using metadata type lvm2
Found volume group "server01" using metadata type lvm2

The problem is my volume group. I set to to server01 on both old and new hard disk. How can I rename old LVM2? How do I access my old hard disk?

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My iptables based firewall allows only port TCP 80 and 443. I also need tcp port # 22, but I do not have static IP at my home. How do I open and close TCP port #22 on demand under Debian or Ubuntu Linux based server systems? How do I install a port-knock server called knockd and configure it with iptables to open tcp port #22 or any other ports?

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I am the small business owner and runs my own web-site. I have noticed increased cracking activity against by blog. What’s the best way to block WordPress URLs such as example.com/blog/wp-login.php and example.com/blog/wp-admin/ in the nginx web-server?

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I have setup an Apache web server on CentOS Linux. How do I configure firewall to allow or block access? How do I setup firewall for a web server under RHEL or CentOS Linux v6.x?

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A properly configured firewall can greatly increase the security of RHEL / CentOS based system. How do I configure a shorewall based firewall for CentOS or Red Hat Enterprise Linux system with an Internet connection? How do I install and configure shorewall to protect the following small business network?

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How do I install the ipset extension to Netfilter/iptables on Red Hat Enterprise Linux / CentOS Linux v6.x?

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