![8vl3onvznkopxa6ny9995yrc4gw[1]](https://i0.wp.com/www.krazyworks.com/wp-content/uploads/2021/10/8vl3onvznkopxa6ny9995yrc4gw1-175x150.jpg "Awk & sed Snippets for SysAdmins")
Books have been written on the subject of awk and sed. Here’s a small sample of commands I put together over the years that are useful for everyday system administration tasks. Most of these tasks …
Read the full story »Dealing with Full Filesystems
Filled up filesystems is a recurring condition eating up sysadmin time on a regular basis. Some studies show that filesystems running out of space are responsible for most day-to-day issues handled by IT departments. Disk …
Quickly Grow EMC Celerra Filesystem
As we all know, Celerra and its kin can get a bit annoying with their “filesystem over 90%” warning emails. Enabling the “autoextend” feature for the filesystems is one option, but if you are a control …
Watch the Log
In the past few days my Postfix server has been having occasional problems talking to the mail gateway. They problem would come and go. The Postfix server would timeout trying to connect to the gateway and keep …
Bash scripting: lists and random things
Imagine you have an HPC cluster with a hundred compute nodes named node001-node100. The two commands below will help you generate a list of node names – either all name on one line or one name per …
iPhone Stopped Syncing with Google Calendar
A small but potentially annoying problem: on rare occasions, your iPhone/iPad may decide your calendar looks full enough and will stop syncing with your Google calendar. This is a situation where:
Calendar sync between your iDevice and …
Install Pflogsumm PostFix Log Summarizer
Pflogsumm is yet another log analyzer/summarizer for Postfix. It is written in Perl and has been around for a while. Very simple to install, so I writing this post mostly as a note to myself. I added an example cron job with some “grep” syntax to cut the Pflogsumm report down to size by dropping some things I am usually not interested in.
Installing Sendmail Analyzer on RHEL/CentOS
The Sendmail Analyzer can be useful for visualizing your Sendmail/Postfix log. The commands below can be copy-pasted as root on default installations of RHEL and CentOS 5/6 with default Postfix and httpd. If your configuration …
Fast IP Range Scanner in Bash
Just a simple script to scan an IP range and do a reverse DNS lookup. This can be useful for building an inventory of systems on your LAN. Just make sure to give your network …
openlava Quick Test
After years working with PBS and LSF, ran into Jeff Layton’s “Share the Load” review of openlava resource manager in the Feb 2013 issue of the Admin Magazine and nostalgia took over. So I built …
Secure Data Destruction for Unix
What is secure computer data destruction? Simply put, securely-deleted data cannot be recovered by any known technique. But when it comes to data security, things are rarely simple. New data recovery methods are developed every …
SEO for Unix Geeks
So, you are finally done with your new shiny Web site and looking for ecom site integration. Congratulations. There is one small problem: the only two visitors to the site are you and Googlebot. And …
Selecting CMS Software
If you are looking for an open-source content management system, your choices are likely to boil down to these three: Joomla!, WordPress, and Drupal. Professional CMS developers tend to disregard WordPress as a purely blogging …
Jailbreaking My iPhone 4S
An iPhone 4S is a fairly sophisticated computer capable of doing many interesting things. Unfortunately, since most phone users are computer idiots, to preserve its bottom line and the sanity of its tech support staff, Apple imposes severe limitations on what you, as a user, can do with your iPhone or iPad. As a Unix sysadmin I am entirely on Apple’s side on this one. However, it would have been nice if Apple allowed an option of full access in exchange for voluntarily voiding the warranty. For those of us who know what they are doing and are not gonna run in tears to the nearest Genius Bar if something goes wrong…
SSH Login Without Password for a Linux Cluster
Most HPC cluster management utilities will automatically take care of the password-less SSH configuration. However, if you are not so lucky, here are the simple steps to get this working. Keep in mind that, depending …
Filesystem Performance Testing Using dd
Below is a simple script to test filesystem read/write performance using dd with varying blocksize parameter. This can be useful for testing local filesystems as well as network-mounted filesystems. The end result will be a …
Remounting Active NFS Filesystems
Here’s a scenario: you have an NFS client mounting a filesystem from server1. You need to migrate this data to NFS server2 and remount the filesystem from the client to point to the new server. The problem is that there is a user application on the client system that uses the NFS mount, preventing you from unmounting it.
Uninstall PostgreSQL from Ubuntu
Ok, so this is a very simple one: uninstall PostgreSQL running on Ubuntu. There are a bunch of pieces to the database server and just running “apt-get remove postgresql” will still leave you with with a bunch of leftovers
Quick BTRFS Test on OpenSuse 12.2
The recent announcement from Suse Enterprise Linux that Btrfs was production-ready raised some suspicions. The last time I tested btrfs (not very long ago) the primary issues were excessive CPU utilization and filesystem space that seemed to disappear into nowhere. So, as a quick test, I put together an OpenSuse 12.2 (3.4.6-2.10-desktop, OpenSuse 12.2) 64-bit VM (ESX) with one dual-core vCPUs, 4GB RAM, the OS disk and a 6GB striped LVM filesystem consisting of 4 4-GB virtual disks.
A Faster Way to Delete Many Folders
This issue is particularly annoying when dealing with expansive directory structures mounted via NFS. Let’s say you have a directory with ten thousand folders and each of them has more subfolders and files. And you …
Fixing the mount.nfs: rpc.statd is not running Error
The rpc.statd service is used by NFS client to help it recover from loss of connectivity to the NFS server. When rpc.statd is not running, NFS is not able to handle remote file locking. You …
System Recovery: Useful Tools
The following is a brief collection of open-source and/or free tools I regularly use for various system recovery tasks. If the servers you work with have CD drives, I would recommend burning these images onto a CD or DVD. This would save you the trouble of messing with the boot options in the BIOS. More advanced versions of BIOS can mount remote ISO images and boot from those. In most cases, however, this approach requires using the dreaded Internet Explorer an requires Windows.
Commands & Shells »
Synology NAS Hacks
![rhd3hj6zvnqeth7qo8em0alduj0[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/10/rhd3hj6zvnqeth7qo8em0alduj01-80x80.jpg "Synology NAS Hacks")
I’ve been using various Synology NAS devices for many years now, and they’re great. Well, almost. There are a few rough spots that don’t thrill me. These consumer-grade devices are designed to be difficult to …
Finding Duplicate Photos
![9dwz62kvm0gtjya9kwb7pawtk9y[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/10/9dwz62kvm0gtjya9kwb7pawtk9y1-80x80.jpg "Finding Duplicate Photos")
Being a shutterbug and a digital hoarder can get expensive. A couple of days ago, my
TerraMaster D5-300 5-bay DAS crashed. Again. This time it was the power supply. I replaced it only to discover that …
Applications »
Synology NAS Hacks
I’ve been using various Synology NAS devices for many years now, and they’re great. Well, almost. There are a few rough spots that don’t thrill me. These consumer-grade devices are designed to be difficult to …
WordPress: Post-processing of the image failed
![ytioq398kc1wnvvz95uixhcn5ii[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/ytioq398kc1wnvvz95uixhcn5ii1-80x80.jpg "WordPress: Post-processing of the image failed")
This particular WordPress issue appeared with version 5.3 and is refusing to go away. However, the problem here is not with WordPress but with the Apache ModSecurity. The particular ModSecurity rule in question is 200003 …
Data »
Synology NAS Hacks
I’ve been using various Synology NAS devices for many years now, and they’re great. Well, almost. There are a few rough spots that don’t thrill me. These consumer-grade devices are designed to be difficult to …
Finding Duplicate Photos
Being a shutterbug and a digital hoarder can get expensive. A couple of days ago, my
TerraMaster D5-300 5-bay DAS crashed. Again. This time it was the power supply. I replaced it only to discover that …
Monitoring »
NFS I/O Stats with Logging
![tq9mhhd5xy2q0kto2j1785n6odv[1]](https://i1.wp.com/www.krazyworks.com/wp-content/uploads/2021/10/tq9mhhd5xy2q0kto2j1785n6odv1-80x80.jpg "NFS I/O Stats with Logging")
The nfsiostat is an excellent tool for analyzing NFS performance. The only major problem with this utility is that it’s designed to be used interactively. It does not have logging or timestamping capabilities. I needed …
Finding Cron Jobs
![iwoau71okwxqh4jv3k4ook32qps[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/iwoau71okwxqh4jv3k4ook32qps1-80x80.jpg "Finding Cron Jobs")
Cron is an indispensable tool for system administration. The difficulties in working with cron in a large environment stem from its decentralized nature. Cron jobs multiply like rabbits, and keeping track of them is not …
Networking »
NFS I/O Stats with Logging
The nfsiostat is an excellent tool for analyzing NFS performance. The only major problem with this utility is that it’s designed to be used interactively. It does not have logging or timestamping capabilities. I needed …
Inventorying NFS Mounts and Mount Options
![4ucne6vs8m7hqdl0el9ddqd1sql[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/10/4ucne6vs8m7hqdl0el9ddqd1sql1-80x80.jpg "Inventorying NFS Mounts and Mount Options")
As time goes by, NFS mounts multiply like rabbits. Added by many different people over the years, these entries present a dizzying variety of mount options – most are a copy-paste job that makes little …
Editor
Igor
Sr. Unix SysAdmin with twenty years experience supporting Solaris, HP-UX, AIX, IRIX, and Linux servers in a large distributed environment.
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