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Archives for August 2016

CentOS / RHEL : Move a Physical Volume from an existing Volume Group to another Volume Group

by admin

This post describes how to move a Physical Volume from an existing Volume Group to another existing Volume Group. This facilitates the move of data in the PV to the new VG without doing any manual migration. Before moving a PV, you should make sure that the Logical Volumes created on top of such PVs […]

Filed Under: Linux

CentOS / RHEL : How to move a Volume Group from one system to another

by admin

To move a whole volume group from one system to another, the vgexport and vgimport commands can be used. Below example involves the steps to move a volume group named “data_vg” from one system to another. The logical volume from this volume group is initially mounted at /data01. 1. Un-mount the file system If required […]

Filed Under: Linux

The ultimate Linux interview questions : swap

by admin

What is swap space? Swap space in Linux is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the physical memory is full, inactive pages in memory are moved to the swap space. While swap space can help machines with a small amount of RAM, it […]

Filed Under: Interview Questions, Linux

CentOS / RHEL 7 : How to Install GUI

by admin

For the new installation of RHEL 7, GUI doesn’t come with the default installation. If you do not click on the “Software Selection” link and pick “server with GUI” then there will be no GUI after reboot, only “Base Environment ” will be installed. To enable GUI after system installation, you can use the following […]

Filed Under: CentOS/RHEL 7

CentOS / RHEL 7 : Configuring static IP adress using network interface configuration files

by admin

There are various ways you can configure an IP address in RHEL 7. The posts discusses the use of network interface configuration files to configure the IP address. Each physical network device has an associated network interface configuration file. Network interface configuration files are located in the /etc/sysconfig/network-scripts directory. 1. Use the ip addr command […]

Filed Under: CentOS/RHEL 7

CentOS / RHEL : How to determine which SNMP version is being used

by admin

Question :1. What command shows what SNMP Protocol version(s) [1, 2c, 3] I am running on my system? 2. How do change the SNMP version in use? Answer : There is no command to show the current running SNMP version. The snmpd daemon will not show as running in any one particular version, as it […]

Filed Under: Linux

Creating network interface alias for network boot or jumpstart installation at OBP

by admin

Question : How to create a network interface alias at OBP for jumpstart installation or network boot. Solution : Sometimes when we want to do a jumpstart installation or a network boot the default network interface which is selected is not connected to the network. The command ‘boot net – install’ fails to run in […]

Filed Under: Solaris

CentOS / RHEL 6 : Install and Configure SNMPv3

by admin

Steps to configure SNMPv3 1. Install the required packages Install the 2 required packages namely, 1. net-snmp-utils 2. net-snmp-devel # yum install net-snmp net-snmp-utils net-snmp-devel net-snmp-utils is required to use the utility snmpwalk. 2. Configure SNMP version 3 user We need to turn off the agent when running net-snmp-create-v3-user command. # service snmpd stop There […]

Filed Under: Linux

CentOS / RHEL : How to restrict SSH login by time of day

by admin

Question: How to enforce a policy that allows new ssh logins at perticular time of the day only. Outside these access windows no new ssh logins are to be permitted. Solution : PAM Resource Description Login times can be controlled using the Linux Plugin Authentication Method (PAM) pam_time.so module. The pam_time.so module enforces the login […]

Filed Under: Linux

How to run savecore (crash dump) manually in Solaris

by admin

If savecore did not successfully run to retrieve system core image(crash dump) from the dump device during reboot following a system panic it is possible to attempt to retrieve the crash dump manually from the command line. The kernel core image gets copied into the dump device configured by the dumpadm command as part of […]

Filed Under: Solaris

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