System Admin Q & A – XVI

Ques 1: – What is RCRON and where to use RCRON ?

Ans: – rcron is a powerful tool that helps system administrators in setting up cron jobs redundancy and failover over groups of machines. RCRON ensure that a job installed on several machines will only run on the active one at any time. High Availability using RCRON ( One Node will be stamped as Active and Second Node will be stamped as Passive ) , Same cron configuration will be on both , only difference would be active/passive state in a file.

For automatic Switching of active/passive state , we will be using KEEPALIVED Daemon , which utilizes the keepalive signal for communication between 2 nodes. After a signal is sent, if no reply is received the link is assumed to be down.

Ques 2: – What is Content Negotiation ?

Ans: – Load Balancing Clusters operate by having all workload come through one or more load balancing front-ends, which then distribute it to a collection of back end servers. If a node in a load-balancing cluster becomes inoperative, the load balancing software detects the failure and redirects requests to other cluster nodes. Red Hat Cluster Suite provides load- balancing through LVS (Linux Virtual Server).

Ques 3: – What is Puppet ?

Ans: – Puppet is a configuration Tool which is use to automate administration tasks.Puppet Agent(Client) sends request to Puppet Master (Server) and Puppet Master Push Configuration on Agent.

Ques 4: – What is Facter in Puppet ?

Ans: – Sometime you need to write manifests on conditional experession based on agent specific data which is available through Facter. Facter provides information like Kernel version,Dist release, IP Address, CPU info and etc.You can defined your facter also.

Ques 5: – What is Storage Clusters ?

Ans: -Storage clusters provide a consistent file system image across servers in a cluster, allowing the servers to simultaneously read and write to a single shared file system. With a cluster-wide file system, a storage cluster eliminates the need for redundant copies of application data and simplifies backup and disaster recovery. Red Hat Cluster Suite provides storage clustering through Red Hat GFS(Global File System).

Ques 6: – How to enable proxy settings in RSYNC and APT (ubuntu) ?

Ans: – Proxy Settings in RSYNC

# export  RSYNC_PROXY="http://:”
#  export RSYNC_PROXY="http://proxy.nextstep4it.com:8080”

Proxy settings for APT : Edit /etc/apt/apt.conf

Acquire::http::Proxy “http://:“;

Ques 7: – What is Virtual Hosting in Apache ?

Ans: – The term Virtual Hosting refers to the practice of running more than one web site (such as site1.nextstep4it.com and site2.nextstep4it.com) on a single machine. In Apache there are two types of virtual hosting.

1: IP Based Virtual Hosting

2: Name-Based Virtual Host

Ques 8: – What is Glusterfs ?

Ans: – GlusterFS is an open source network / cluster filesystem and based on a stackable user space design. It is used to achieve high availability of storage(i.e real time replication of files) across two linux machines using GlusterFS. Although glusterfs found its application in different areas like cloud computing, streaming media services, and content delivery networks.

Ques 9: – What is mutt and how to send mails using mutt from linux console ?

Ans: – Mutt is a small but powerful text-based e-mail client for Unix like operating systems. With mutt command one can send and read emails. Mutt supports both maildir & mbox mail formats. Mutt is compatible with POP & IMAP protocols.

Syntax :

# mutt -s “Subject of the Mail”  recipient-address@domain.com <  /dev/null

Ques 10: – What is Storage Clusters ?

Ans: -Storage clusters provide a consistent file system image across servers in a cluster, allowing the servers to simultaneously read and write to a single shared file system. With a cluster-wide file system, a storage cluster eliminates the need for redundant copies of application data and simplifies backup and disaster recovery. Red Hat Cluster Suite provides storage clustering through Red Hat GFS(Global File System).

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