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Information about the Hard drive and list all PCI devices

$ hdparm /dev/hda

   /dev/hda:
   multcount = 16 (on)
   IO_support = 0 (default 16-bit)
   unmaskirq = 0 (off)
   using_dma = 1 (on)
   keepsettings = 0 (off)
   readonly = 0 (off)
   readahead = 256 (on)
   geometry = 16383/255/63, sectors = 234375000, start = 0

or for SCSI - $ hdparm -i /dev/sda

/dev/sda:

Model=ST3802110A , FwRev=3.AAJ, SerialNo=9LR2AE39
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs RotSpdTol>.5% }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4
BuffType=unknown, BuffSize=2048kB, MaxMultSect=16, MultSect=?1?
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=156301488
IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5
AdvancedPM=no WriteCache=enabled
Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6,7

* signifies the current active mode

How fast is your drive? - $ hdparm -tT /dev/hda

   /dev/hda:
   Timing buffer-cache reads: 128 MB in 0.41 seconds =315.32 MB/sec
   Timing buffered disk reads: 64 MB in 1.19 seconds = 53.65 MB/sec

Need to find your device?

$ mount
or
$ cat /proc/partitions
or
$ dmesg | egrep '^(s|h)d'

   hda: IC35L120AVV207-1, ATA DISK drive
   hdc: Lite-On LTN486S 48x Max, ATAPI CD/DVD-ROM drive
   hda: max request size: 1024KiB
   hda: 234375000 sectors (120000 MB) w/7965KiB Cache, CHS=16383/255/63, UDMA(100)

If you want to turn on dma - $ hdparm -d1 /dev/hda

   setting using_dma to 1 (on)
   using_dma = 1 (on)

List all PCI devices - $ lspci -v

   00:00.0 Host bridge: ATI Technologies Inc Radeon Xpress 200 Host Bridge (rev 01)
        Subsystem: Intel Corporation Device d600
        Flags: bus master, 66MHz, medium devsel, latency 64
        Memory at (64-bit, non-prefetchable)
        Kernel modules: ati-agp

   ... lots more ...

   Note, there is also lspci -vv for even more information.

Squid proxy Cache Result Codes

TCP_HIT
A valid copy of the requested object was in the cache.

TCP_MEM_HIT
A valid copy of the requested object was in the cache, AND it was in memory so it did not have to be read from disk.

TCP_NEGATIVE_HIT
The request was for a negatively-cached object. Negative-caching refers to caching certain types of errors, such as "404 Not Found." The amount of time these errors are cached is controlled with the negative_ttl configuration parameter.

TCP_MISS
The requested object was not in the cache.

TCP_REFRESH_HIT
The object was in the cache, but STALE. An If-Modified-Since request was made and a "304 Not Modified" reply was received.

TCP_REF_FAIL_HIT
The object was in the cache, but STALE. The request to validate the object failed, so the old (stale) object was returned.

TCP_REFRESH_MISS
The object was in the cache, but STALE. An If-Modified-Since request was made and the reply contained new content.

TCP_CLIENT_REFRESH
The client issued a request with the "no-cache" pragma.

TCP_IMS_HIT
The client issued an If-Modified-Since request and the object was in the cache and still fresh.

TCP_IMS_MISS
The client issued an If-Modified-Since request for a stale object.

TCP_SWAPFAIL
The object was believed to be in the cache, but could not be accessed.

TCP_DENIED
Access was denied for this request

UDP_ codes

"UDP_" refers to requests on the ICP port (3130)

UDP_HIT
A valid copy of the requested object was in the cache.

UDP_HIT_OBJ
Same as UDP_HIT, but the object data was small enough to be sent in the UDP reply packet. Saves the following TCP request.

UDP_MISS
The requested object was not in the cache.

UDP_DENIED
Access was denied for this request.

UDP_INVALID
An invalid request was received.

UDP_RELOADING
The ICP request was "refused" because the cache is busy reloading its metadata.

ERR_ codes

"ERR_" refers to various types of errors for HTTP requests. For example:

ERR_CLIENT_ABORT
The client aborted its request.

ERR_NO_CLIENTS
There are no clients requesting this URL any more.

ERR_READ_ERROR
There was a read(2) error while retrieving this object.

ERR_CONNECT_FAIL
Squid failed to connect to the server for this request.

dotnet on Linux

Mono provides the necessary software to develop and run .NET client and server applications on Linux, Solaris, Mac OS X, Windows, and Unix. Sponsored by Novell (http://www.novell.com ), the Mono open source project has an active and enthusiastic contributing community and is positioned to become the leading choice for development of Linux applications.

Frequently Asked Questions
Contacting the Mono Team
Bug reporting
Articles and Tutorials on Mono.

Mono is a cross platform, open source .NET development framework.

Mono allows your existing binaries to run on Linux with copy-deployment.

Features
Multi-platform.
Based on the ECMA/ISO standards .
Runs ASP.NET and Winforms applications.
Can run .NET, Java, Python and more .
Open Source, Free Software.
Commercially supported.
Comprehensive technology coverage

Encrypt CD/DVDs

This guide can be adapted to any distro, its not Ubuntu specific.

Installing necessary tools
sudo apt-get install aespipe mkisofs loop-aes-utils

Chose a password
You need to chose a 20+ character password and DO NOT FORGET IT, you will NEVER get your data back if you forget the password.

Creating the CD/DVD image
Make a directory called backup then copy the files you want to burn into the backup directory.
We are using AES encryption, you can chose from 128 or 256 bit key lengths, I recommend 256.

mkisofs -r backup | aespipe -e aes256 > backup.iso

or for 128 bit key length
mkisofs -r backup | aespipe -e aes128 > backup.iso

Mounting the image
First we need to load some modules

sudo modprobe aes
sudo modprobe cryptoloop

For 128 bit key lengths:
sudo mount -t iso9660 backup.iso /mnt/iso -o loop=/dev/loop0,encryption=aes128

For 256 bit key lengths:
sudo mount -t iso9660 backup.iso /mnt/iso -o loop=/dev/loop0,encryption=aes256

This will mount the image in /mnt/iso (make sure you have the directory before you try to mount)

Burning
You can burn the image with your favorite program (gnomebaker, k3b), you might get some warnings about the image but you can ignore them.

Mounting the new CD/DVD
First make sure you loaded the aes and cryptoloop modules (see above)
sudo mount -t iso9660 /dev/cdrom /mnt/iso -o loop=/dev/loop0,encryption=aes256

Reference: Here

Kernel parameters for enhance security

The following list shows tunable kernel parameters you can use to secure your Linux server against attacks.

For each tunable kernel parameters you need to be add it to the /etc/sysctl.conf configuration file to make the change permanent after reboots. To activate the configured kernel parameters immediately at runtime, use:
# sysctl -p

Enable TCP SYN Cookie Protection

A "SYN Attack" is a denial of service attack that consumes all the resources on a machine. Any server that is connected to a network is potentially subject to this attack.

To enable TCP SYN Cookie Protection, edit the /etc/sysctl.conf file and add the following line:
  net.ipv4.tcp_syncookies = 1

Disable IP Source Routing

Source Routing is used to specify a path or route through the network from source to destination. This feature can be used by network people for diagnosing problems. However, if an intruder was able to send a source routed packet into the network, then he could intercept the replies and your server might not know that it's not communicating with a trusted server.

To enable Source Route Verification, edit the /etc/sysctl.conf file and add the following line:
  net.ipv4.conf.all.accept_source_route = 0

Disable ICMP Redirect Acceptance

ICMP redirects are used by routers to tell the server that there is a better path to other networks than the one chosen by the server. However, an intruder could potentially use ICMP redirect packets to alter the hosts's routing table by causing traffic to use a path you didn't intend.

To disable ICMP Redirect Acceptance, edit the /etc/sysctl.conf file and add the following line:
  net.ipv4.conf.all.accept_redirects = 0

Enable IP Spoofing Protection

IP spoofing is a technique where an intruder sends out packets which claim to be from another host by manipulating the source address. IP spoofing is very often used for denial of service attacks. For more information on IP Spoofing, I recommend the article IP Spoofing: Understanding the basics.

To enable IP Spoofing Protection, turn on Source Address Verification. Edit the /etc/sysctl.conf file and add the following line:
  net.ipv4.conf.all.rp_filter = 1

Enable Ignoring to ICMP Requests

If you want or need Linux to ignore ping requests, edit the /etc/sysctl.conf file and add the following line:
  net.ipv4.icmp_echo_ignore_all = 1
This cannot be done in many environments.

Enable Ignoring Broadcasts Request

If you want or need Linux to ignore broadcast requests, edit the /etc/sysctl.conf file and add the following line:
  net.ipv4.icmp_echo_ignore_broadcasts = 1

Enable Bad Error Message Protection

To alert you about bad error messages in the network, edit the /etc/sysctl.conf file and add the following line:
  net.ipv4.icmp_ignore_bogus_error_responses = 1

Enable Logging of Spoofed Packets, Source Routed Packets, Redirect Packets

To turn on logging for Spoofed Packets, Source Routed Packets, and Redirect Packets, edit the /etc/sysctl.conf file and add the following line:
  net.ipv4.conf.all.log_martians = 1

References: Network Security with /proc/sys/net/ipv4