Bandwidth Conversion Calculator
Most ISP (Internet Service Provider) and Datacenters giving you 2 types of bandwidth calculations: metered or unmetered. An ISP in Indonesia for example has internet packages which have data transfer quota (also means metered) and unlimited data transfer (also means unmetered). Same does with datacenters, usually they offer a server with specified monthly data transfer quota or capped unmetered bandwidth.
As user we must be a little bit smart on deciding whether we will subscribe for metered or unmetered bandwidth. In the case of renting server on a datacenter, usually they put your server on 100Mbps port if you subscribe for metered bandwidth. In other side, most datacenter cap your bandwidth in the range of 1Mbps to 10Mbps (depends on datacenter) so your server can only use up to that range even the network card on your server is 100Mbps NIC.
Apache Can’t Load Modules Problem
Today I’m having problem with CPanel’s Apache when I upgrade it. The Apache server won’t start, it gives this error messages:
Syntax error on line 216 of /usr/local/apache/conf/httpd.conf: Cannot load /usr/local/apache/libexec/mod_bwlimited.so into server: /usr/local/apache/libexec/mod_bwlimited.so: cannot open shared object file: No such file or directory /etc/init.d/httpd start: httpd could not be started
Obviously that the module mod_bwlimited.so cannot be found by Apache, here is how to fix it:
cd /usr/local/cpanel/apache /usr/local/apache/bin/apxs -iac mod_bwlimited.c
After compile finish the .so file will be copied to the right directory and you can start Apache by executing command:
service httpd start
Importing Multiple CSV Files to MS Access Database
I got a task to convert a lot of .csv (Comma Separated File) files today. There are hundreds, 970 files to be exact 
of CSV files. MS Access does have feature to import CSV file to its table, but if you want to convert 970 files one by one, it will took a damn long boring time.
Luckily all the CSV files have the same column format, so what I need to do is find how to automate the process instead of doing it in barbaric way (convert it one by one). I know that this is doable with macro script.
Synchronizing Server Date and Time Using rdate
You can sync or update the date and time of your linux server by using rdate command. rdate command will the check the time server and compare the date time on your server to the time server.
If there is time difference, rdate will update your server date time. To update your server date time run this command:
rdate -s <timeserver></timeserver>
The list of time server can be found on this website: http://www.eecis.udel.edu/~mills/ntp/clock1a.html use the one that near with your server location.
Since my server is in Singapore then I use this command:
rdate -s nets.org.sgTo set the hardware clock to match with your system clock, you can use this command:
/sbin/hwclock --systohc
Website Speed Test
How fast is your website load? That is the question I’ve been asking these days. On my computer my website is load quite fast. But my question is how about other computers or visitors from other continents? Do they having the same browsing experience with me when they visit my website?
Customizing Bash Prompt
I install several servers 2 days ago, what I found after I login to SSH is that the bash prompt is different with my older server, it only show “bash-3.1#” instead of “[username@servername – directory] $”
I found “bash-3.1#” is difficult as I don’t know my current directory location. With a little bit Google search I get an answer.
You can customize your bash prompt by creating a file named .bash_profile (there is a “dot” in front of the filename)
Insert this code in .bash_profile file:
export PS1="[u@h w]$ "
now your bash prompt will look like this:
[user@localhost /home/user]$
Creating Empty File with Specified Size
If you want to do some download speed test, you can create a dummy file which have specific file size. To create an empty file with size you want type this command:
dd if=/dev/zero of=10mb-file.bin bs=1024k count=10
The command above will create a 10 MB sized file. If you want to create another file with different size, change the number after “count=”. Any number given after “count=” will be multiplied by 1024k or 1MB.
Transferring Files from Remote Server to Remote Server Using SCP
If you have more than one server and want to transfer files between the two, you can use SCP (Secure Copy). Here is how to do it:
$ scp /folder/file-to-tranfer username@remote.host.net:/folder/file-destination-name
SCP then will ask the password for username on the remote host that already specified, insert the username and press enter. Wait until the transfer finished and your file will be copied to the destination server.