Security and technology

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The nature of the attacks will be different: the targets, tactics and
results. Security is both a trade-off and an arms race, a balance between
attacker and defender, and changes in technology upset that balance.

- Bruce Schneier, Security in Ten Years

Popular posts from this blog

Linux IPC and Limits

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Note: POSIX implementation provides better and cleaner api to IPC compared to System V. Prefer using POSIX api if you are known to be running on 2.6 or later kernel. System V IPC implementation on Linux includes Shared memory, Semaphores and Message queues. There are system imposed limits that are important to keep in mind when developing application/services in Linux. To know the limits use ipcs command. For example on my system: [root@f7 ~]# ipcs -l ------ Shared Memory Limits -------- max number of segments = 4096 max seg size (kbytes) = 32768 max total shared memory (kbytes) = 8388608 min seg size (bytes) = 1 ------ Semaphore Limits -------- max number of arrays = 128 max semaphores per array = 250 max semaphores system wide = 32000 max ops per semop call = 32 semaphore max value = 32767 ------ Messages: Limits -------- max queues system wide = 16 max size of message (bytes) = 8192 default max size of queue (bytes) = 16384 Or via sysctl interface: kernel.shmmni = 4096 kernel.shmal
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htop: more than top. pstree: ps with tree.

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I'm a big fan of procexp and other sysinternals tools on Windows. Many people who use those and then come to Linux complain that there are no such tools in Linux. Most people are familiar with top and ps commands. I would like to introduce you to a bunch of utilities on Linux that are very useful while debugging issues. Lets start with htop, a better alternative to top. You can install htop on a yum based system like Fedora, Redhat, CentOS etc with "yum -y install htop" or with "apt-get install htop" on systems that are debian apt based like Ubuntu. htop is much better in displaying the process and resource information than top. It gives a more accurate and clearer picture of process memory usage than top. A screenshot of htop in action: It has many interesting features. It's display layout is refreshing different and nice. It can show tree view, a very important feature to understand the ancestry of a process. In the size column, the MB part is hig
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Access Apache WebDAV from Windows XP

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This is a work-in-progress. This is not complete, may be never will be. It is purely for my own reference. Use at your own risk. Here I try to remember how to configure Apache and Windows XP so that WebDAV on Apache is accessible from Windows XP clients. Links: http://www.thrrrust.com/~pclark/blog/2005/03/fun-with-windows-xp-and-webdav.html http://www.hss.caltech.edu/help/unix/admin/web/apache-webdav-xp http://support.microsoft.com/?kbid=909423 http://www.greenbytes.de/tech/webdav/webdav-redirector-list.html Registry changes required to support large files and many files: http://support.microsoft.com/default.aspx/kb/900900/ http://support.microsoft.com/?kbid=912152 Automatic Protocol Driver Selection for MSDAIPP http://msdn2.microsoft.com/en-us/library/ms691698.aspx http://msdn2.microsoft.com/en-us/library/ms691696.aspx http://msdn2.microsoft.com/en-us/library/ms691722.aspx DHTML Behaviors for making webfolder open automatically. http://dean.edwards.name/moz-behaviors/ http://msdn.micr
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