Author: Minto Joseph

fsfreeze in Linux

The fsfreeze command, is used to suspend and resume access to a file system. This allows consistent snapshots to be taken of the filesystem. fsfreeze supports Ext3/4, ReiserFS, JFS and XFS. A filesystem can be frozen using following command: #…

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Using strace to debug application errors in linux

strace is a very useful tool which traces system calls and signals for a running process. This helps a lot while debugging application level performance issues and bugs. Aim of this post is to demonstrate the power of strace in…

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Troubleshooting a Multipath Issue

Multipathing allows to configure multiple paths from servers to storage arrays. It provides I/O failover and load balancing. Linux uses device mapper kernel framework to support multipathing. In this post I will explain the steps taken to troubleshoot a multipath…

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Debugging high CPU usage using Perf Tool and Vmcore Analysis

There are several tools and technologies available to debug deeper into high CPU utilization in a system; perf, sysrq, oprofile, vmcore, and more. In this post, I will narrate the course of debugging a CPU utilization issue using technologies like perf…

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Some observations on Puppetrun with foreman

After joining Pythian I was introduced to several configuration management systems and Puppet was one of them. Foreman is a system management tool which can be integrated with Puppet to manage puppet modules and to initiate puppet runs on hosts…

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Auditing files in Linux

Stat command in Linux can be used to display a file or a file system status. I came across an issue in RHEL4 where a file’s ‘Change time’ is far ahead than the ‘Modification time’ without a change in uid,…

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