Display Information and Parameters of Hard Disk Drives on CentOS

# smartmontools
# -a, -all: Prints all SMART information about the disk
/usr/sbin/smartctl -a /dev/<device>

# hdparm - get/set hard disk parameters
/sbin/hdparm /dev/<device>

pppoe[pid]: Bad TCP checksum someValue on CentOS

From /var/log/messages
The reason it happens is because you have short circuted the modem to the hub and the pppoe protocol or software have trouble keeping things in sync because of timeouts that were generated by the network collisions. The solution is to seperate the modem network from the home network so no collisions will happen. However, the CLAMPMSS=no could also help since it can reduce overheads and thus lower timeouts (if any)though i didn't check that. other things can help like increasing timeouts, hanging synchronization options but it would be cheaper by time/money to just buy another ethernet card and be done with it.

1. vi /etc/sysconfig/network-scripts/ifcfg-ppp0

..
CLAMPMSS=no
..

2. /sbin/iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu

Setup NAT server on Linux

1. change the value of ip_forward from 0 to 1

CentOS

echo "1" > /proc/sys/net/ipv4/ip_forward


Ubuntu

sudo vi /etc/sysctl.conf
--
..
net.ipv4.ip_forward=1
..

sudo sysctl -p # load sysctl settings

2. load related modules

/sbin/modprobe ip_nat_ftp
/sbin/modprobe ip_conntrack
/sbin/modprobe ip_conntrack_ftp
/sbin/modprobe ip_conntrack_irc

3. 192.168.1.1 ~ 192.168.1.254 route through ppp0

/sbin/iptables -t nat -A POSTROUTING -o ppp0 -s 192.168.1.0/24 -j MASQUERADE

4. if you want the above things done every time you boot the machine, you can add these into /etc/rc.local

Setup aMule's Webserver on CentOS

Although there is a RPM of aMule for RHEL5 and CentOS, it has only aMule main program. If you would like to remote control your aMule server, you must have aMuleWeb installed. For CentOS users, you have to compile the sourcecode of aMule by yourself because aMuleWeb is compiled at the same time you compile aMule by using the --enable-amuleweb flag when you run configure.

1. Download sourcecode from http://www.amule.org/files/files.php?cat=34 and extract it
2. Install below packages for compiling environment
zlib-devel, wxGTK-devel, gettext-devel, gcc-c++
3. Check http://www.amule.org/wiki/index.php/Configure for all available parameters
./configure --prefix=/usr --enable-webserver --enable-amulecmd --enable-amule-daemon --enable-cas --enable-wxcas --enable-alc --enable-alcc
4.

make # It takes much long time
make install

5. Run aMule from desktop or shell
6. Go to "Preferences"
Enable "Accept External Connections"
Enter a password for External Connections. This is for external programs like amulecmd and amulegui
Enable "Run amuleweb on startup"
Type a password into "Full right" field. This is the password that you want to type when you login
7. Restart aMule in order to make the changes to take effect.
8. Remember to open 4711 port of the firewall so that you can open aMuleWeb in a browser by entering the URL, http://ip:4711

To handle RAR files on CentOS


yum install rar unrar

After installing the two packages, your default archive manager will support RAR format

Set an alarm at a specified time on CentOS


at 23:00 2005-09-15
at> /usr/local/bin/alarm
at> ..
at> # multiple commands can be executed at same time
at> ..
at> <EOT> # pressing CTRL + D means save and exit


atq #lists the user's pending jobs


ERROR 400: Bad Request while MoBlock try to wget level1.gz list

This is caused by the server for that list not working with wget's time-stamping option ( parameter -n )
A workaround is to update the list manually without time-stamping:

cd /var/spool/moblock/cache/dl/
wget http://www.bluetack.co.uk/config/level1.gz

then run the guardian.p2p rebuild process