nixCraft Linux Sys Admin Blog

Read the Fine Print on "Open Source" Software

Posted: 12 May 2008 10:58 AM CDT

There is some good discussion going on about open source software licenses and confusion. From the article:

Back in the 1980s, when Richard Stallman was the only one talking about the need for "free software," no one quite knew what he was talking about. That's not just because people looked askance at someone who said it would be possible to write a version of Unix that could be given away for free, along with all of the compilers, editors, and utilities that a typical Unix installation included.

Stallman also managed to confuse people with the term "free" -- he used it as a political statement, saying "free as in freedom," or "free as in 'free speech'," contrasting it with "free as in 'free beer'." But no matter how hard he tried, Stallman was faced with the reality that most people thought of "free software" as programs for which you didn't have to pay money. The fact that Stallman's software was indeed designed to be given away without charge only added to the confusion.

=> Read the Fine Print on "Open Source" Software ( via Linuxtoday )

Understanding SELinux ( Security-Enhanced Linux )

Posted: 12 May 2008 10:32 AM CDT

Nice introduction to SELinux and other option to enhance Linux security. Mandatory access control and role-based access control are relatively new to the Linux kernel. With the introduction of the LSM framework, new security modules will certainly become available. In addition to enhancements to the framework, it's possible to stack security modules, allowing multiple security modules to coexist and provide maximum coverage for Linux's security needs. New access-control methods will also be introduced as research into operating system security continues. From the article:

Linux has been described as one of the most secure operating systems available, but the National Security Agency (NSA) has taken Linux to the next level with the introduction of Security-Enhanced Linux (SELinux). SELinux takes the existing GNU/Linux operating system and extends it with kernel and user-space modifications to make it bullet-proof. If you're running a 2.6 kernel today, you might be surprised to know that you're using SELinux right now! This article explores the ideas behind SELinux and how it's implemented.

=> Anatomy of Security-Enhanced Linux (SELinux) Architecture and implementation

Linux File System Limitations For High Performance Computing

Posted: 11 May 2008 08:14 PM CDT

Linux file systems have a number of limitations that make them a poor choice for large and high-performance computing environments. This article explains some of the pros and cons of Linux and old UNIX file systems:

I am frequently asked by potential customers with high I/O requirements if they can use Linux instead of AIX or Solaris.

No one ever asks me about high-performance I/O -- high IOPS (define) or high streaming I/O -- on Windows or NTFS because it isn't possible. Windows and the NTFS file system, which hasn't changed much since it was released almost 10 years ago, can't scale given its current structure. The NTFS file system layout, allocation methodology and structure do not allow it to efficiently support multi-terabyte file systems, much less file systems in the petabyte range, and that's no surprise since it's not Microsoft's target market.

=> Linux File Systems: You Get What You Pay For

What do you think?

Debian / Ubuntu Package Troubleshooting: subprocess post-removal script returned error exit status xx

Posted: 11 May 2008 06:47 PM CDT

Here is a quick way to fix half installed packages under Debian / Ubuntu Linux.

If you see an error while removing or installing debian / ubuntu package that read as follows:

(Reading database ... 147148 files and directories currently installed.)
Preparing to replace octopussy 0.9.6.2 (using octopussy_0.9.6.2_all.deb) ...
Unpacking replacement octopussy ...
dpkg: warning - old post-removal script returned error exit status 10
dpkg - trying script from the new package instead ...
dpkg: error processing octopussy_0.9.6.2_all.deb (--install):
subprocess new post-removal script returned error exit status 10
dpkg: error while cleaning up:
subprocess post-removal script returned error exit status 10
Errors were encountered while processing:
octopussy_0.9.6.2_all.deb

In above octopussy package is not getting removed because of script error. Mostly these are shell script written using /bin/sh. These scripts called with -e option which means if not interactive, exit immediately if any untested command fails. The exit status of a command is considered to be explicitly tested if the command is used to control an if, elif, while, or until; or if the command is the left hand operand of an && or || operator. In short shell scripts will abort with an error if something fails. To fix this problem visit /var/lib/dpkg/info directory
# cd /var/lib/dpkg/info
Now find out files in following format:
packagename.*
octopussy.*
$ ls octopussy.*
Now open each file and find out line that read as follows:
#/bin/sh -e
Replace with
#/bin/sh
Save and close all the files. Now run apt-get / dpkg command again to remove package:
# apt-get --purge remove octopussy
OR
# dpkg -r octopussy