Archives for October 2015

Besides the RAM there is a so called Swap, which is a virtual memory, where RAM content (pages) could be swapped-in in case there is not enough RAM available anymore. This swap is located on the disc and since disc reads and writes are slower than reading from RAM, accessing memory pages there will result […]

The “sosreport” is a tool to collect troubleshooting data on RHEL/CentOS systems. It generates a compressed tarball of debugging information that gives an overview of the most important logs and configuration of a Linux system, to be sent to Redhat Support. Among other things, the sosreport includes information about the installed rpm versions, syslog, network […]

The lsof command lists open files, sockets, and pipes. You can use lsof command to see what files are held open (such as libraries or log files) and what ports daemons listen to. You can search for open files using lsof command. lsof should be run as the superuser (root) to see all open files. […]

The post mentions few ways to exactly identify/match the LUN presented from SAN with underlying OS disk. Method 1 Execute command below command to obtain Vendor, Model and Port, Channel, SCSI-ID, LUN # cat /proc/scsi/scsi Host: scsi2 Channel: 00 Id: 00 Lun: 29 Vendor: EMC Model: SYMMETRIX Rev: 5874 Type: Direct-Access ANSI SCSI revision: 05 […]

The post describes the steps to replace a mirror disk in a software RAID array. In this example, we have used /dev/sda1 as the known good partition, and /dev/sdb1 as the suspect or failing partition. Before proceeding, it is recommended to backup the original disk. Before removing raid disks, please make sure you run the […]

Kdump is an advanced crash dumping mechanism. When enabled, the system is booted from the context of another kernel. This second kernel reserves a small amount of memory, and its only purpose is to capture the core dump image in case the system crashes. Since being able to analyze the core dump helps significantly to […]