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Adding LUNs to VXVM on Linux

Igor — Tue, 06 Sep 2011 18:03:30 +0000

The following is a brief overview of the process for adding LUNs to VXVM under Linux. In our example we have an RHEL 5 server with existing LUNs and VXVM volume groups. Two new LUNs with multipathing were allocated from SAN and need to be added to the system to grow one of the volumes and the corresponding filesystem.

Facebook Security for the Lazy

Igor — Thu, 28 Apr 2011 06:36:19 +0000

Posted in Featured Security

Every time you use Facebook, you probably have a nagging feeling in the back of your head that someone other than your friends is reading your posts. You should trust that feeling. At the same time, keep in mind that Facebook is a tool designed primarily for sharing personal information with large groups of people you barely know. Facebook is not your personal diary or a substitute for SMS. You just need to assume that everything you post on Facebook inevitably will end up in the hands of someone you don't like very much. And then you proceed based on that assumption.

Don’t Be Afraid to Reboot Unix Servers

Igor — Tue, 22 Feb 2011 00:11:26 +0000

Posted in Disaster Recovery Featured

Reboot your Unix servers after making any major changes to the production environment. Should an unexpected problem come up, it will be easier to deal with it when everything is still fresh in your mind and not six months down the road, when you have to do a reboot to replace a failed system board and suddenly discover that some application wouldn't load, by which time you forgot all about this application and have to start with the first page of the admin guide.

Windows 7 Black Screen After Booting

Igor — Tue, 05 Oct 2010 08:07:37 +0000

Posted in Disaster Recovery Networking Samba

I had to power-cycle my Windows 7 64-bit laptop. The bootup sequence looked normal and reached a point where I could see the black screen with the mouse cursor. After this stage my desktop would usually appears, but not this time. I could move the mouse and I could even establish a remote desktop connection to my laptop. But I could not log in. Every time it would reach the same point - the black screen with the mouse cursor - and it would stop.

NFS “Not Owner” Error

Igor — Tue, 31 Aug 2010 03:34:52 +0000

Posted in Commands & Shells Filesystems Networking

The "not owner" error is displayed on the client system (usually Solaris) when attempting to mount an NFS share from a server. This error may appear even though the share is correctly exported and the client system has full access. If you are getting a "permission denied" error, then this article is not for you and you should check here instead.

How to Really Kill Computer Viruses

Igor — Sun, 21 Feb 2010 10:34:20 +0000

Posted in Applications Disaster Recovery

How do you know if your computer has a virus? Is it connected to the Internet? Then it has a virus. Many computer viruses and other malicious applications are very resilient and will actively resist any attempts to deactivate and remove them. Some viruses can even delete your antivirus application or prevent it from working properly. Many viruses cannot be effectively removed once they are loaded in memory and active.

Forcing Linux to Reboot

Igor — Fri, 29 Jan 2010 19:21:35 +0000

Posted in Commands & Shells Filesystems

Until I branched out a few years ago from supporting Unix server to working with Linux clusters, I never really encountered this issue: you type "reboot", "init 0", or "shutdown" as root and... nothing happens. Or the system starts going down but then hangs on unmounting a filesystem or unloading a module. I think this happened once to a colleague of mine who was rebooting a Solaris server, but this is a common problem with Linux.

Upgrading from Vista to Windows 7

Igor — Thu, 28 Jan 2010 02:45:24 +0000

Posted in Applications Backups Disks and Volumes

Recently I upgraded a client's Vista computer (Toshiba Qosmio, 4Gb, Intel Core Duo P7350, 7200-RPM 200-Gb disk) from Vista Ultimate 64-bit to Windows 7 Ultimate 64-bit. Being a Unix sysadmin this is not something I usually do. How did the experience compare to upgrading HP-UX, Solaris or SLES? In a nutshell: I'd rather walk around all day in wet underwear than attempt to upgrade Vista ever again.

NetBackup Command Guide

Igor — Sun, 27 Dec 2009 23:17:07 +0000

Posted in Backups Veritas

NetBackup is an enterprise-level distributed backup and recovery application. The environment consists of the master server, media server, storage library, networking hardware, and client agents. NetBackup supports a wide variety of Unix, Linux, VMS, and Windows systems. The original backup solution was developed by Control Data Corp., later acquired by Openvision, which gave the product its "NetBackup" name. NetBackup was then bought by Veritas and is currently owned and supported (poorly) by Symantec.

Copying Data: Are We There Yet?

Igor — Sun, 27 Dec 2009 23:12:12 +0000

Posted in Backups Networking Performance Veritas

I am sure this will sound familiar: you are copying a large amount of data - either locally or over the network - and you are wondering how long it will take and if there is a way to make things go faster.You may be surprised, but it does matter what type of files you are copying: 1Gb-worth of many small files will take considerably longer to copy than two 500Mb files. The hardware you are using is an important consideration, but it's not the only factor limiting data transfer speed.

Testing Filesystem Performance with Bonnie++

Igor — Fri, 10 Jul 2009 20:33:51 +0000

Posted in Disks and Volumes Filesystems Performance

Bonnie++ is a benchmark utility designed to test performance of hard drives and filesystems by simulating various types of disk I/O. Bonnie++ may be used to test local disks as well as network-mounted filesystems. It ...

Numeric File Permissions in Unix

Igor — Sat, 27 Jun 2009 23:50:44 +0000

Posted in Commands & Shells Files

Suppose you are working with a Web server and your task is to make sure that no files or directories have permissions “777″. It would be easy to just recursively change permissions for all files ...

Partitioning System Disk

Igor — Fri, 25 Jul 2008 00:25:03 +0000

Posted in Disks and Volumes

When performing a new Unix OS installation you are usually presented with a choice of accepting the default partitioning layout or going into advanced settings and defining your own partitions. The default layout will normally ...

Linksys WAP54G Secure Configuration

Igor — Wed, 11 Jun 2008 17:09:26 +0000

Posted in Security Wireless

Below are some basic steps to secure a wireless access point (WAP). The screenshots are for Linksys WAP54G v. 3.04, however, the same steps will apply to wireless access points from other manufacturers. Understand this: ...

Dealing With Disk Hogs

Igor — Sun, 01 Jun 2008 21:49:29 +0000

Posted in Commands & Shells Files

Some users and application developers believe that any free disk space on the server belongs to them. Suddenly you get an email alert saying that a server “xyz” ran out of disk space in /home. ...

Tips on dealing with the Bagle rootkit

Igor — Mon, 26 May 2008 21:51:00 +0000

Posted in Disaster Recovery

Normally I don’t concern myself with Windows- related matters. However, the infamous Bagle rootkit and its numerous variations deserve some attention even from Unix sysadmins. Bagle annoyed me and my customers long enough. Essentially, Bagle ...

VxVM Recovery Cheatsheet for Solaris

Igor — Thu, 15 May 2008 22:22:36 +0000

Posted in Disks and Volumes Veritas

This is a quick-and-dirty guide to recovering VxVM volumes and filesystems on a Solaris server. These instructions are not intended to be an in-depth troubleshooting guide for the Veritas Volume Manager. This is just something ...

Highly redundant array configuration

Igor — Thu, 08 May 2008 19:58:03 +0000

Posted in Disks and Volumes Featured

The cost of storage arrays is falling along with the quality of their manufacture. To quote Lev Andropov from the “Armageddon”: “Components. American components, Russian Components, ALL MADE IN TAIWAN!” What in the nineties used ...

Dealing with ReiserFS bad blocks

Igor — Mon, 24 Mar 2008 23:42:14 +0000

Posted in Filesystems

The following is a procedure for recovering a ReiserFS filesystem with bad blocks. If this is a system FS and cannot be unmounted, the box needs to be booted from the latest version of Knoppix ...

ReiserFS Filesystem Recovery

Igor — Fri, 21 Mar 2008 20:55:45 +0000

Posted in Disks and Volumes

The this is a description of a method for recovering ReiserFS filesystems from failed disks with bad blocks, when other recovery methods (reiserfsck) will not work. For this example, the failed server is called node1 ...

Distributed password cracking with Medussa

Igor — Wed, 10 May 2006 19:43:29 +0000

Posted in Applications Security

Medussa is a password cracking application that supports distributed processing. One node acts as the Medussa server and the rest of the nodes are running the client application. The server node, in addition to running ...

Mountpoint permission problem in Solaris

Igor — Thu, 04 May 2006 23:45:43 +0000

Posted in Filesystems

The following condition was originally discovered in OpenSolaris 11 (Bug ID: 4697677). This problem occurs when you do mkdir -m 700 on a mountpoint before mounting it. This superceeds whatever permissions you might give ...