Archive
Posts from 2009
Securing Linux file systems that don't contain executables
Linux comes with a slew of mount options, several of which are useful for locking down what can and can't happen inside a file system. Three options I find super useful are noexec, nosuid and nodev. The noexec option disables execution for files that reside within a file system, nosuid disables execution of setuid executables inside a file system, and the nodev option instructs the file system not to interpret character or block special files. These options make a lot of sense for file systems such as /tmp, /home and /var, since these file systems typically don't need to contain executables or device files…
$ read more →Making sense of cron in Centos and Fedora Linux
CentOS and Fedora Linux use a set of directories in /etc to control when jobs run. These directories take the following form: To add a job to run hourly, daily, weekly or monthly, you can drop an executable shell script in the pertinent directory. I recently became curious which time of the day daily jobs execute, which day weekly jobs run, and when monthly jobs were scheduled. The answer to these questions comes in the way of /etc/crontab, which contains crontab formatted entries that call the run-parts script to invoke the scripts in the hourly, daily, weekly or monthly directory.
$ read more →Viewing PCI bus throughput on Solaris systems
The PCI and PCI express interconnect technologies have become the defacto standard for connecting peripherals to most motherboards. 64-bit 66 MHZ PCI interconnects run with speeds up to 528MB/s, and share the available bandwidth between devices on the PCI bus. PCI express x32 runs with speeds up to 8 GB/s, and provides dedicated "lanes" to connect each peripheral directly to the motherboards chipsets. This allows PCI express devices to utilize all of the available bandwidth, and maximizes throughput since PCI express devices do not need to compete with other devices on the bus…
$ read more →Ridding myself of cat hair and cat allergies
I have had my cat T-bone for close to 13 years, and she has been with me through the many phases and places of my life. Always chipper and upbeat, her crazy antics are amusing to say the least. But, as much as I love her, I seriously hate how much she sheds and the allergies that I have developed while owning a cat. Since I dig my cat and couldn't bear to get rid of her, I have tried numerous things to reduce the allergens she created…
$ read more →Securing CentOS and Fedora installations
I have been doing some Redhat and CentOS security research, and came across several AWESOME links on securing Linux installations: Hardening RHEL5 NSA reference guide for securing Linux installations NSA Guide to securing Linux installations Stack overflow protection with ExecShield
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