How To Resize /dev/shm Filesystem In Linux?

From http://www.walkernews.net/2010/05/04/how-to-resize-devshm-filesystem-in-linux/

By default installation, RHEL and most Linux distributions mount tmpfs (a RAM-based temporarily filesystem) to /dev/shm directory and this temporarily filesystem size is always set to be half of the installed memory.

If that default size is not something expected, you can increase or reduce the /dev/shm filesystem size at wish.

Display Number of Processors (CPUs) on Linux

If you’ve just upgraded your Linux box, or you are wondering how many processors a remote server has, there’s a quick and dirty command you can use to display the number of processors.

On Linux, /proc/cpuinfo contains all of the processor information for all current processors in your computer. This will include the speed, the amount of on-chip cache, processor type, and how many cores.

Here’s the command:

cat /proc/cpuinfo | grep processor | wc -l

The command just looks in the /proc/cpuinfo file, pulls out the number of lines containing the word “processor” and passes them into wc (word count), which returns a count of the CPUs in the system.

Here’s what it returned on my remote server:

[root@root]# cat /proc/cpuinfo | grep processor | wc -l

4

Note that if you have a dual-core processor, it will return each core as a separate processor. You can look at the full output of cat /proc/cpuinfo to see if the chips are dual-core.

How to know what is the type of OS: 32-bit or 64-bit?

myserver:/home/oracle:>cd $ORACLE_HOME/bin
myserver:/ora/app/oracle/product/11.2.0.1/bin:>file oracle

oracle: setuid setgid ELF 64-bit LSB executable, AMD x86-64, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked (uses shared libs), for GNU/Linux 2.6.9, not stripped

Verifying Which Ports Are Listening

Once you have configured services on the network, it is important to keep tabs on which ports are actually listening on the system’s network interfaces. Any open ports can be evidence of an intrusion.

Linux Tips and Tricks

To find out what a particular driver/module does you can usually use the modinfo command:
# modinfo -d e1000
Intel® PRO/1000 Network Driver
#
# modinfo -d hangcheck-timer
Hangcheck-timer detects when the system has gone out to lunch past a certain margin.
#

Guide to Linux File Command Mastery

A crash course in Linux file commands for the newly initiated
Although GUI desktops such as KDE and GNOME help users take advantage of Linux features without functional knowledge of the command-line interface, more power and flexibility are often required. Moreover, a basic familiarity with these commands is still essential to properly automate certain functions in a shell script.