Linux/ Centos7/ Tech Info

Backend servers Varnish has a concept of "backend" or "origin" servers. A backend server is the server providing the content Varnish will accelerate. Our first task is to tell Varnish where it can find its backends. Start your favorite text editor and open the relevant VCL file. Somewhere in the top there will be a section that looks a bit like this.: # backend default { # .host = "127.0.0.1"; # .port = "8080"; # } We remove the comment markings in this text stanza making the it look like.: backend default { . host = "127.0.0.1" ; . port = "8080" ; } Now, this piece of configuration defines a backend in Varnish called  default . When Varnish needs to get content from this backend it will connect to port 8080 on localhost (127.0.0.1). Varnish can have several backends defined you can even join several backends together into clusters of backends for load balancing purposes.

Get Your Website Response TIME For HTTP Site Copy the following command and run it from your shell for X in `seq 6`; do curl -Ik -w "HTTPCode=%{http_code} TotalTime=%{time_total}\n" http://example.com/ -so /dev/null; done For HTTPS Site for X in `seq 6`; do curl -Ik -w "HTTPCode=%{http_code} TotalTime=%{time_total}\n" https://example.com/ -so /dev/null; done

Check os version in Linux The procedure to find os name and version on Linux: Open the terminal application (bash shell) For remote server login using the ssh:  ssh user@server-name Type any one of the following command to find os name and version in Linux: cat /etc/os-release lsb_release -a hostnamectl Type the following command to find Linux kernel version: uname -r

About NFS (Network File System) Mounts NFS mounts work to share a directory between several servers. This has the advantage of saving disk space, as the home directory is only kept on one server, and others can connect to it over the network. When setting up mounts, NFS is most effective for permanent fixtures that should always be accessible. Setup An NFS mount is set up between at least two servers. The machine hosting the shared network is called the server, while the ones that connect to it are called ‘clients’. This tutorial requires 2 servers: one acting as the server and one as the client. We will set up the server machine first, followed by the client. The following IP addresses will refer to each one: Master: 12.34.56.789 Client: 12.33.44.555 The system should be set up as root. You can access the root user by typing sudo su Setting Up the NFS Server Step One—Download the Required Software Start off by using apt-get to install the nfs programs. yum install

1. How to find the A record of а domain. Command line: $ nslookup example.com 2. How to check the NS records of a domain. Command line: $nslookup -type=ns example.com 3. How to query the SOA record of a domain. Command line: $nslookup -type=soa example.com 4. How to find the MX records responsible for the email exchange. Command line: $ nslookup -query=mx example.com 5. How to find all of the available DNS records of a domain. Command line: $ nslookup -type=any example.com 6. How to check the using of a specific DNS Server. Command line: $ nslookup example.com ns1.nsexample.com 7. How to check the Reverse DNS Lookup. Command line: $ nslookup 10.20.30.40 8. How to change the port number for the connection. Command line: $ nslookup -port=56 example.com 9.How to change the timeout interval for a reply. Command line: $ nslookup -timeout=20 example.com 10. How to enable debug mode. Debug mode provides important and detailed information both for the q