The Tech Bench: A few of our favorite links
When troubleshooting client servers, there are a few sites that the ServInt MST seems to go back to again and again. Whether it’s a reference page or a testing tool, the links below are just a few of the valuable resources our MST uses on a daily basis. And if you you’ve got a favorite, we’d love to hear about it.
intoDNS.com This a great little tool that looks into the health and configuration of your DNS and suggests any needed fixes. This is a great place to start when troubleshooting DNS issues or just checking the status of your nameserver setup.
MX Toolbox This site contains a few free tools for dns, nameserver, mx and whois lookups along with a bunch of other specific lookups in their SuperTool beta.
Traceroute tutorials on exit109.com Running a traceroute is an important part of troubleshooting a slow network connection. If you’re interested in digging a little deeper into networking and your server, this page is for you. It contains a great tutorial with just about everything you always wanted to know about running a traceroute and interpreting the output.
DNSstuff.com This is another site where you can complete a WHOIS lookup, run a traceroute or find IP information.
Exim Cheatsheet If you’re interested in something a little more advanced, this is a reference some of our techs use when troubleshooting Exim mail servers.
And of course there are our own resources. We have our KnowledgeBase as well as this very blog Series, The Tech Bench. And for our customers, the ServInt Forums are a great place to look for answers that our customers have found to many tech questions.
We hope you find these links as useful as we do. But if it’s all just a little overwhelming, don’t worry, that’s what we’re here for.
Note: By including a link on the list above, ServInt is not endorsing the purchase of any paid-for service. Also, though we tend to find the above links helpful, ServInt has no control over the accuracy of any third-party content or tools.
The Tech Bench is an ongoing blog series featuring the answers to common questions the ServInt MST fields everyday. You can also find more great tech tips in the ServInt KnowledgeBase.
The Tech Bench: Jailshell in cPanel
Jailshell is a level of shell (SSH) access that limits a user to his or her specific directory structure. Under regular SSH when users log into their servers they are taken to their home directory and can execute commands within their directory structure.
Under SSH, that user can also travel to any directoy on the server and even use “ls” to get a directory listing, they just cannot open the files or interact with them. Jailshell, on the other hand, logs users into their directory structure and locks them in (much like a prison or jail cell), disallowing them from openly traversing the directory structure outside of their home.
Jailshell is easily implementable in cPanel. You can switch an account’s shell access in WHM by navigating to Manage Shell Access, under the Account Functions header. Read more
The Tech Bench: Controlling spam and mistakenly blacklisted IPs
Editor’s Note: For this week’s Tech Bench, we thought we’d share the particulars of a recent MST ticket. If you’ve ever struggled with administering email for clients over your VPS, this is one’s for you.
Recently, a customer submitted a ticket to the MST asking for help with the email on his VPS. It quickly came to the attention of our Director of Network Compliance, Mike Witty, when the customer explained that all email going through the mail delivery IP address on his server was being blocked by AOL, Gmail and AT&T.
The reason given by the email services for blocking his IP address was that it was a suspected source of spam. Yet the customer was in contact with all the users on his VPS and knew that they were not sending out spam.
The Tech Bench: The Ins and Outs of Nameservers
Nameservers are a small, but important part of your web service. They are essentially programs that translate your domain into an IP address and vice versa. They do this so that Internet users do not have to remember 32 bit IPv4 addresses such as 123.45.67.89 or 128 bit IPv6 addresses that are far longer. They instead allow us to recall and input the familiar .com domain names for all of our favorite websites.
Every domain name needs to be listed on a nameserver somewhere. There are three kinds of nameservers to choose from: nameservers run by your web host, third-party nameservers (typically, people use the nameservers run by their domain registrar if they have third-party nameservers), and private nameservers you run on your hosted server. But which to choose?
Read more
The Tech Bench: File Permissions and Ownership
After last week’s discussion of PHP handlers, we thought we’d use this week’s Tech Bench to discuss the ins and outs of file permissions and ownership.
The Numbering Scheme
File permissions are often noted as a three digit number. This number is the binary shorthand used to classify the owner, group and public permissions for the file. The value farthest to the left is for the file owner, the middle value is for the group, and the value on the right is for anyone who does not fit into the owner or group and in most circumstances should be the most restricted.
The Tech Bench: All About PHP Handlers
What are PHP handlers?
In order for a site to run on PHP, the server must interpret the PHP code and generate a page when visitors access the website. It interprets the code based on which PHP library you are using, such as PHP 4 or PHP 5. A PHP handler is what actually loads the libraries so that they can be used for interpretation. PHP handlers determine how PHP is loaded on the server.
There are multiple handlers that can be used for loading PHP: CGI, DSO, suPHP, & FastCGI. Each handler delivers the libraries through different files and implementations. Each file and implementation impacts Apache’s performance, because it determines how Apache serves PHP.
It is essential for your server’s performance that you select the handler that fits your situation. Selecting the right handler is just as important as the PHP version itself. One handler is not necessarily better than another; it depends on your unique setup.
Note: In the event that your server runs multiple versions of PHP, you may assign different PHP handlers to each individual instance of PHP. For example, version 5 may be handled by CGI while PHP 4 is handled by DSO.
How to change the handler
Changing the handler on cPanel is very easy to do and takes only seconds. Log into WHM and navigate to: Main >> Service Configuration >> Configure PHP and SuExec
You simply select your PHP handler choice from the drop-down menu. Then hit “Save New Configuration”.
Note: If you do not see your desired choice in the drop-down menu, it may need to be compiled on the server first. You can do this via the EasyApache script of WHM.
List of PHP handlers
The Tech Bench: How can I troubleshoot “500 Internal Server Error” issues in cPanel/WHM?
500 Internal Server Errors can be caused by many issues. Please be advised if you are using Internet Explorer as your browser, it is known to display an internal server error when there isn’t one. Try using another browser first to eliminate this possibility.
If you are using a different browser, then the error may be due to one of the following: permissions/ownerships of files, memory usage, or coding (.htaccess, premature end of script, software specific).
To troubleshoot the 500 internal error you need to be ready to work on the command line via an SSH connection to your server. Read more
