22 August 2017

How To Solve : "550 Please turn on SMTP Authentication in your mail client.."

I have a hosting server to manage with exim as the mail server. Recently, one of our customer faced an error when he try to send email to his domain email in the server. Every time he send email, the email failed to send with an error "550 Please turn on SMTP Authentication in your mail client..".

He do not use Microsoft Outlook and accessing his email directly by using webmail. After wandering around the internet, I've finally found the solution, and it is quite simple.

Here are the steps :

1. Login to the WHM, and find a menu called Edit MX Entry.
2. Find the domain which can't receive email.
3. Change the Email Routing from "Automatically.." into "Local Mail Exchanger"
4. Click Save and the domain now should be able to receive email again.

How To Solve : "Function mb_substr() does not exist"

I recently faced an script error "Function mb_substr() does not exist". When I checked, there was already mbstring PHP module, installed in my WHM/cPanel based server. But the module didn't work. So why? 樂

Apparently, the mbstring is an additional PHP module that must be activated separately by your own hand. To activate this module, login to your cpanel and find menu "Select PHP Version". Find module called mbstring and check the checkbox, and then click Save.

Now, your script should work.

18 July 2017

My Linux Filesystem / Home Folder Suddenly Becomes Read Only? Don't Panic !

Recently, I've found an odd error in my Linux machine : My home folder and my entire Linux system suddenly becomes read only! I tried to reboot my machine, and the system failed to boot. I was panic and ridiculously thought, that my Linux machine was being hacked.

I reinstalled my machine and the error gone, but later, the error showed up again. After googling around, I've finally known that I had some bad sectors in my harddisk. What I did to solve was just using this fsck command :
sudo fsck -a /dev/sda

Wait until the process done, and your Linux machine will be back to normal.

12 July 2017

Unsuspend Not Working in WHM Based Web Hosting [Solved]

I am currently a web admin with WHM and cPanel based web server. Recently I faced an odd error : the unsuspend function not working in WHM. I have tried to suspend and unsuspend again the account, but the result is zero.

Apparently, there is an unknown error in WHM scripts or something about it. What I have finally done to solve the problem is by executing these commands through SSH :

1. Check the suspend status :

/scripts/suspendacct username -cek-

You will get an output that the account is apparently still suspended.

2. Unsuspend the account :
/scripts/unsuspendacct username

18 May 2017

How To Check Your Server From DDoS, and How To Solve.

If you are a Linux server administrator, you might need to know how to check your server from DDoS attack. There is no clear explanation why some people do a DDoS attack. Maybe they just want to test your server. Whatever they are, you have to be technically prepared for this issue.

1. Check who are accessing your server right now
netstat -anp |grep 'tcp\|udp' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n

You will get output like this :

2. The IP that is accessing your server most is the suspected one. Next, you should block the IP by executing this command :
route add suspected_ipaddress reject