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Question: How do I lookup the wwn address of my HBA card installed on the Linux system. I need this information to create zoning on my fiber channel switch. Answer: Use one of the following methods to view the HBA WWN address on Linux. Method 1: /sys/class/scsi_host/host{n}/device/fc_host:host{n}/port_name File On Redhat 5 and above (including OEL [...]


How to Allow MySQL Client to Connect to Remote MySQL server

By default, MySQL does not allow remote clients to connect to the MySQL database. If you try to connect to a remote MySQL database from your client system, you will get “ERROR 1130: Host is not allowed to connect to this MySQL server” message as shown below. $ mysql -h -u root -p Enter [...]


Question: I have purchased Linux support for RHEL and OEL from Oracle corporation. How do I register my Linux system to Oracle support network to download and update packages? Can you explain me with step-by-step instruction? Answer: After purchasing Linux support from Oracle, you should register your Linux system with Oracle’s Unbreakable Linux Network using [...]

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Unix Shell Script to Execute Oracle SQL Query

Question: Can you provide me a shell script that will accept oracle credentials, sql query to be executed and displays the output? Answer: The shell script given below prompts some basic information and displays the output of the SQL. You can use the same concept and hard-code some of these values in the shell-script itself [...]


Question: While downloading using wget, I get the following error “Connecting to <URL>.. failed: Connection refused.”. I’m behind a proxy server. How do I fix it? Answer: Export the http_proxy variable with your proxy server name or ip address and then try downloading as explained below. Connection refused error while using wget If http_proxy environment [...]


Question: When I’m trying to ssh to a remote server, after I enter the username, it takes a lot of time before it displays the password prompt. Basically, my SSH ( openSSH ) is slow during authentication process. How do I solve this problem? Answer: If your ssh login from localhost to remotehost is slow, [...]


Question: How do I view all the current iptables rules? Once I view it, is there a way to delete all the current rules and start from scratch? Answer: Use the iptables list option to view, and iptables flush option to delete all the rules as shown below. You should have root permission to perform [...]


You may want to disable ping replies for many reasons, may be for a security reason, or to avoid network congestion. Someone can flood the network with ping -f as shown in “Ping Example 5” in our earlier Ping Tutorial article. If ping reply is disabled we can avoid this flooding. Disable ping reply Temporarily [...]