Posts by Minto Joseph

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 pinning down an application bug. I came across an issue in which nagios was sending…

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 issue. This should provide an glimpse into the tools and technology involved. Problem was reported…

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 and vmcore. Following sar output is from a system which faces high %system usage. [root@prod-smsgw1…

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 from web interface. This is very useful if you want to configure large number of…

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, gid and mode. # stat /etc/php.ini File: `/etc/php.ini’ Size: 45809 Blocks: 96 IO Block: 4096…