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 …
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Postfix »
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. Read the full story »
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 …
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 …
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
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.
Dealing with Blank Lines in WordPress functions.php
This is an annoying little problem plaguing many WordPress themes: blank lines in the themes’ functions.php cause various random issues. The most common manifestation of this condition is the failure to save the “image” custom field. Below are a few commands to apply a quick fix. Unfortunately, these steps would need to be repeated every time you upgrade your theme, until the developers catch on. To simplify this task, I arranged the commands into a little script that will create a backup of your original functions.php and make the necessary changes.
Simple Shell Random Password Generator
A very simple script to generate a random secure password of desired length. This can come in handy when setting up multiple user account and/or lacking imagination.
Solaris 10 SVM/SDS Mirrored Root Disk Replacement
The following is a standard process for replacing a failed boot disk mirrored with SVM on a Solaris 10 Sun server. Your hardware must support hot-swappable disks for this process to be performed without booting into single-user mode.
Generate Encrypted Password for /etc/shadow
Here is a simple way to generate an encrypted password string for use in Linux /etc/shadow, among other things. This is just in case you don’t wish to use the usual tools for changing the password (passwd, chpasswd).
Import CSV into Excel Spreadsheet via OLEDB
The following is a quick how-to explaining the process of importing an external CSV file into an existing Excel spreadsheet. This approach can be very handy if your CSV data is updated regularly by some external application. Keeping the formatting in the spreadsheet and pulling fresh data from a separate CSV is the way to go. The instructions below are for Excel 2010 running on Windows 7 64-bit. Command syntax for other versions of Excel and other platforms may differ.
Use wget with Your Rapidshare Account
If you have a Rapidshare premium account, you can use wget to download files. The process is two-fold: first, you need to use wget with your Rapidshare username and password to obtain and store the Rapidshare cookie; then, you can use wget with the cookie file to download a list of links.
Configure Postfix to Use Gmail for Sending
Here is a simple script to help you configure Linux postfix to use your Gmail account for sending emails. The script has been tested on OpenSuse 11.4 and 12.1, but should work find on any recent Linux disro. The only requirement is that you have postfix insalled.
Show Allocated / Used Filesystem Space Summary
On servers with many filesystems calculating filesystem space utilization summary can get very tedious. Below is a simple script that will summarize all filesystems and provide you will the totals for allocated and used space in GB.
A Simple Process Monitoring Script
Let’s say you are running a data restore. Things are moving along, but network is congested and the backup server is overloaded. You really don’t feel staring at the restore status for the next several hours and just want to be notified when the process completes. The simplest method of monitoring for processes starting or ending on Unix systems is by using “ps” with a “while” loop.
Compress Old Log Files on Linux
Most log files located in /var/log are part of the log rotation and will be compressed automatically. However, in many cases various user applications maintain log files outside of /var/log. These logs are not managed …
Testing SSH Connectivity to Multiple Servers
Imagine a hypothetical scenario: you support hundreds of remote servers and you need to check which server you can access via SSH and which servers are not letting you log in. Doing this manually is a tedious process that many sysadmins choose to skip. The inevitable outcome is inability to quickly access a system when it really counts.
Disable Usage Information Sharing on iPhone
Carrier IQ is software installed on your iPhone by Apple at the request of the service providers. This system utility collect detailed usage and location data on your phone and sends it to the service providers. Supposedly, this was done to improve quality of service. In reality, however, if any such improvement actually occurred, it was only a side-effect.
Fun with Call Forwarding
Sometimes you don’t want people to reach you on your phone, but you don’t want to do something obvious, like turning the phone off. Because then they’ll just leave you a message and you will still be expected to call back. Below is a list of phone number in various US area codes that you can use to forward your unwanted calls.
Simple Host Monitoring with SSH
Sometimes you just need something very simple to monitor a server or an application on a temporary basis. A basic ping monitor is fine, but it will only tell you if a server is responding on the network. It will not tell you if there is some other problem on the system. The script below relies on passwordless SSH setup to periodically log into the monitored nodes and check on their health by executing a local or remote script.
Viewing “man” Pages in a Web Browser
The Unix “man” pages are an indispensable tool even for the most experienced of sysadmins. Unfortunately, in a terminal window the text may be hard to read and getting a hard copy to take with you down to the datacenter will really test your Unix skills. The following quick script will convert the “man” page of your choice into formatted text and open it in the Web browser.
Event Log »
Dell Changes Up OpenStack Cloud Plans
In a major announcement from Dell yesterday, the company announced that its public cloud ecosystem and strategy will be centered on partners Joyent, ScaleMatrix and ZeroLag, and will emphasize recent acquisition Enstratius. The announcement represents …
Improving U.S. Weather Prediction With Petascale Supercomputing
Over at the Washington Post, Jason Samenow writes that an infusion of funding into the National Weather Service from Hurricane Sandy relief legislation promises to facilitate massive upgrades to key supercomputers, dramatically improving local, national, …
Google and NASA Collaborate on AI Research With New Quantum Supercomputer
Google and NASA have teamed up to launch a new laboratory focused on advancing machine learning. The Quantum Artificial Intelligence Lab — hosted at NASA’s Ames Research Center in California — will contain a quantum …
Your Cloud Provider Is Toast. Now What
Your cloud provider is great. Your cloud provider is cheap. Your cloud provider is out of business.
Now what do you do
If your favorite consumer cloud service goes out of business or simply feels it’s time …
Best Linux Tools for Enterprise Developers and Systems Administrators
It’s a testament to Linux’s ubiquity and versatility today that so many “best of” lists are published focusing on the free and open source operating system.
Just in the past few months here on Linux.com, for …
Networking »
Red Hat: Changing Hostname and IP
Changing hostname and IP is frequently required when a server is being moved from testing or development to production. The process is a fairly simple one, but steps must be performed in a certain order to avoid complications.
Troubleshooting InfiniBand Connections
The following is a brief troubleshooting guide for an InfiniBand network found in common HPC Linux clusters. Running these commands requires OFED 1.5.2 or later package installed on your systems. Additionally, the “pdsh” (parallel shell) command is part of the HP CMU cluster management software (version 4.2.1 used in our example) installed on the head node.
Applications »
OpenSUSE 11.4 Installation Overview
After enjoying taking apart Microsoft’s “cloud” Office 365 for the numerous shortcomings of its installation process, having to do the same for my favorite Linux distro – openSUSE – is rather upsetting. OpenSUSE installation routine went from nearly-flawless in 11.1 to mildly annoying in 11.3, arriving to moderately obnoxious in 11.4. What happened? Same as with Microsoft, poor installation workflow is to blame. One can always feel when desktop support people take over workflow tasks from server admins.
Microsoft Launches Office 365. Fails.
To much fanfare Microsoft launched its first “cloud” version of the Office – the Office 365. Silly name, I know, but I still decided to give it a shot. Call me an optimist, but sometimes I feel there is a chance Microsoft will come out with a product more useful than Xbox 360. For the sake of brevity, let me just say that Office 365 was not that product. I can’t really tell you how good or bad it is, because I never got past the convoluted installation procedure. My many years of experience as a sysadmin did not help.
Data »
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.
Searching Large Network-Mounted Filesystems
Recently I ran into a small problem: I needed to find recently-modified files in a very large NFS filesystem. One of the high-level folders contained dozens of sub-folders with thousands of files in each. There is a significant performance penalty associated with placing such directory structures on network-mounted filesystems. Running the “find” command at the top of the filesystem would have taken over an hour and the problem here was not available bandwidth, but the time it takes for the “find” to request and receive attribute information for each folder and file.
Monitoring »
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 …
Changing Process CPU Affinity on Linux
A common real-life scenario: on a multi-CPU system Oracle processed have taken over and the system has ground to a crawl. The average system load is in double-digits and even logging in takes several minutes. The possible root causes for the problem can range from inefficient SQL queries (the common problem) to insufficient system resources. But at this point you just need to make the system a bit more responsive, so you can start troubleshooting.
Commands & Shells »
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 …
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.
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Igor
Sr. Unix SysAdmin with fifteen years experience supporting Solaris, HP-UX, AIX, IRIX, and Linux servers in a large distributed environment.
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