To test your disk’s performance, use the hdparm utility. This program’s main purpose is to display and set various ATA parameters that influence performance. The program can also run basic performance tests. The -t parameter tests disk read speed, while the -T parameter tests Linux’s disk cache performance. The cache speed is important to overall disk performance, but for purposes of testing, you don’t want the cache to interfere with raw disk performance tests. You can combine the two tests, and hdparm will apply correction factors to separate the two measures. Following the -Tt parameter, you specify the hard disk you want to test as follows:

# /sbin/hdparm -Tt /dev/hdb

In order to get reliable results, you should perform these tests on a system that’s otherwise not doing much, and especially not performing any disk-intensive tasks.
What’s poor performance? This depends on the disk. You should be able to find detailed specifications for your disk on the manufacturer’s website. You need to find the specification for sustained transfer speeds to and from the disk’s media.

If you believe your disk speed is deficient, you should search for a reason for the problem. In the case of ATA disks, the -v parameter to hdparm produces a summary of disk settings:

# /sbin/hdparm -v /dev/hdb

The most important setting displayed by this output is the using_dma item. This setting reveals whether the controller is using direct memory access (DMA) mode, in which the controller directly transfers data between the disk and the computer’s memory. The alternative is programmed input/output (PIO) mode, in which the computer’s CPU mediates all transfers. DMA mode is generally faster than PIO mode, and DMA transfers impose a lower CPU load, so disk accesses should not slow down CPU-intensive programs as much.

If Linux isn’t running your disks in an optimal mode, you can use hdparm to adjust its settings. In some cases, you can apply driver-specific options to your ATA driver. Finally, one issue of disk performance doesn’t relate to speed, but it is important to laptop users: energy use. You can configure the disks to spin down when they haven’t been accessed for some time, thereby saving energy.

Normally, a computer’s hard disks spin whenever the computer is turned on. This feature makes disk access swift, because there’s no need to begin spinning the disk to access a file; however, it consumes a fair amount of power. Therefore, spinning down a disk when it’s not in use is helpful. Doing so is particularly helpful on laptop computers, on which a spinning hard disk can greatly reduce battery life. hdparm supports the -S option to set this feature.

Value Meaning

0 Power-saving mode disabled; disk never goes into low-power mode.

1–240 Time in 5-second multiples; for instance, 12 means 60 seconds.

241-251 Units of 30 minutes (241), 60 minutes (242), and so on through 5.5 hours (251).

252 21 minutes.

253 Drive-specific timeout value.

255 21 minutes and 15 seconds.

For instance, to set the disk to power down after ten minutes of inactivity, you could type the following command:

# hdparm -S120 /dev/hda

Linux Commands/Tools Tips

http://portswigger.net/suite/download.html

Burp suite allows an attacker to combine manual and automated techniques to enumerate, analyze, attack and exploit web applications. The various burp tools work together effectively to share information and allow findings identified within one tool to form the basis of an attack using another.

http://www.owasp.org/index.php/OWASP_WebScarab_NG_Project

WebScarab-NG is a complete rewrite of the old WebScarab application, with a special focus on making the application more user-friendly. To this end, WebScarab-NG makes use of the Spring Rich Client Platform to provide the user interface features. By using the Spring Rich Client Platform, WebScarab-NG automatically gains things like default buttons, keyboard shortcuts, support for internationalisation, etc.

Another new feature is that session information is now written into a database, rather than into hundreds or thousands of individual files. This makes disk space utilisation and things like archiving of sessions a lot easier.

Ultimately, WebScarab-NG will have all the significant functionality that the old WebScarab had, although it will be reorganised quite significantly, in order to make the application more user friendly.

The user interface has changed quite a lot from the old WebScarab. Apart from the new default Look&Feel (JGoodies), you will see that the conversation viewer has changed quite a lot. The old “Raw” view is still there, but the Parsed version has changed quite dramatically – for the better, I hope you’ll agree!

The Parsed view now shows the request and response details in a tree form, rather than in individual text boxes. This makes the interface look a lot cleaner, and more importantly, is a lot more compact. It also makes it a lot easier to include features like automatically breaking out URL parameters, and multiple cookies into their own nodes, where it is a lot easier to view the individual parameters. We also show the request and the response next to each other, rather than one above the other, since most people seem to have more horizontal real-estate than vertical. The split between request and response can easily be adjusted by dragging, as can the split between the headers and the message content

 

One of things that seperates Ubuntu (or Debian based distribution) from other Linux distributions is that it disables the root account. For other distros such as Red Hat and SUSE, you are prompted for root password when it’s needed to perform a job or execute a command. You just log on as root or change to root with su. Since Ubuntu doesn’t have any root password by default, you use sudo to run a command as root. sudo allows access to root with controls over what a person can do as root. sudo prompts you for your password, which allows regular users to have some root access without knowing the root password.

The default sudo configuration in Ubuntu can be found in the /etc/sudoers file. It should always be edited with the visudo tool, not any standard text editor, as it perform extra validation checks for syntax errors. The default sudoers file looks like this:

# User privilege specification
root ALL=(ALL) ALL

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

The first rule allows root to use sudo to become any other user on the system, and the second rule allows anyone who is a member of the admin group to run any command as root. So when you want to run a command as root on a default Ubuntu system, type sudo followed by the command to run. For instance if you wanted to run apt-get update as root, you would type:

$ sudo apt-get update

To limit permissions for a user when using sudo, we can specify which applications it can run as root. For instances:

pavs ALL=(root) /usr/bin/find, /bin/rm

In this example the user pavs can only use the command “find” and “rm” as root.

However most users from other distros would probably prefer using su instead of sudo. To do that in ubuntu just set a password for root: $ sudo passwd root . Now you can log in as root or use su and sudo. You have the best of all worlds. ;)