Archive for December, 2010

Unix and Linux File system Inodes

If you have worked with Unix or Linux dedicated servers, you might have heard the term inode and not paid it much attention. Each object of a Unix or Linux file system is represented by an inode. The inode contains information about the file and its attributes and may include the following details:

File […]

Password Protect an Apache Web Directory

Apache HTTP Server is versatile and modular, and it is very easy to add global configurations. For individual website users, it is also easy to add site-specific settings using .htaccess files. Password protecting a directory is no exception. This is useful for multi-user web servers or even for a server that has […]

How to Hide Files from Apache Directory Listings

Apache HTTP Server comes with a useful feature for file viewing called “directory listing” or “directory browsing”. With this feature enabled, users who visit a directory without an index file will see a list of the files in that directory, as well as information about them. This is useful for HTTP download mirrors […]

How to Hide Apache Header Information

One of the features of Apache that can sometimes be a liability is the web server header. This is an identification string that is sent to user agents. By default, Apache will tell the world about your Apache version, modules that you have installed, and even your operating system and version. Attackers […]

How Many IP Addresses Do I Need?

As you may have heard, there are a finite number of IP addresses available to Internet Service Providers (ISP). Once they are all used up, the only way to get more is to reassign them. In technical terms, the limited number of IP addresses refers to the IPv4 address space, while there is […]

5 Password Tools for Servers

Ideally, your server should be an impenetrable fortress, but recent DDoS attacks highlight the security problems even companies that pay thousands or millions to protect their websites face. Nevertheless, nothing is worse than having your server crippled by someone who simply guessed your password. In no particular order, here are five tools to […]

Advantages of Web-based Application Servers

An application server is a dedicated server that runs a central application or numerous applications, allowing clients to connect through an intranet or over the Internet. In traditional application server models, the software of the server and client was usually the same or similar, and the client machine required a smaller client application to […]

Transferring Your Data to the Cloud

Cloud computing has not yet taken over the server industry, and there are plenty who are resisting all attempts. Nevertheless, the usage of cloud services and hybrid cloud deployments has increased gradually, and anyone who uses dedicated servers and has some type of web presence should at least take a look at it.
One of […]

5 Horrible Server Security Practices

There are plenty of horrible ways to get your server hacked, cracked, botnetted, malwared, spammed, virus infected, and any number of awful scenarios, but some are worse than others. I have more sympathy for a server administrator who is subjected to SQL injections and other stealthy, even sinister plots. They probably did not […]

Local DNS vs. Hosted DNS Service

DNS, which stands for Domain Name System is one of the most important components of a dedicated server. In fact, DNS is so important that the Internet itself would not function without it. If your dedicated server lacks DNS, no one but you will be able to reach it. The question up […]

Trace Process Issues with strace

This week and last, we have been discussing ways to monitor server processes, applications, and network activity. Presumably, these tools will tell you that your system is running fine or lead you to the software causing the problem. If it is software you are intentionally running that is causing the problem, you may […]

Apache “Graceful Restart” Message in Log Files

If you happen to scan the web server log files of your dedicated server, as I have often recommend, you might come across a message saying something like, “[notice] Graceful restart requested, doing restart”. The first important thing to know about this message is the word “notice”. This means that it is not […]

Dstat System Resource Statistics

Over the past two weeks, we have covered a few ways to monitor your Linux dedicated server, from the CPU usage of processes to website bandwidth. In order to get a true understanding of how your server is using or misusing resources, however, you need to use multiple monitoring tools, namely: vmstat, iostat, netstat, […]

Monitor Bandwidth with BandwidthD

Bandwidth is not free, and if you were to believe everything ISPs said, you might believe a war over bandwidth will be as violent as one fought over oil. With ISPs throttling bandwidth, and hosting companies fighting for every last cent of bandwidth, it is no surprise that the word bandwidth can strike fear […]

More Port Analysis with lsof

Last week we looked at two Unix/Linux commands that you can use to find out more information about open ports and the processes running on them. Another useful tool for process analysis is “lsof”, which stands for “list open files”. The command itself can be used for many tasks on your dedicated […]

The Value of SPF Records

SPF stands for Sender Policy Framework, and it is the standard established in RFC 4408. Essentially, SPF validates emails sent to a mail server to determine if a message is spam. One of the biggest problems faced by ISPs trying to fight spam is the spoofing of IP addresses and domains. In […]

A Quick Guide to DNS Lookup

DNS lookup is a good tool for general domain inquiries, server testing, and for following security leads. It is easy to do, and most Linux and Unix dedicated servers come with the commands you need. All you have to do is log on via SSH and get started.
The first command you can use […]

Listening for Programs on Server Ports

On a Linux or Unix dedicated server, applications that access the Internet must do so using ports. Think of a port, as the name implies, as a window to the outside world. Without a port, a program will not have outside access, and outside computers will not have access into your server.
When configuring […]

Managed vs. Unmanaged Servers

One of the biggest decisions you’ll make when deciding to get a dedicated server is whether you will use a managed server or unmanaged server. On the surface, the differences are clear: a managed server, like those offered by, are systems in which your service provider, to some degree, takes care […]

Server Software Behaving Badly

When your dedicated server’s software starts acting up, it may get to the point where you want to trash the whole thing and give up. You should fight that urge, however, and try to find out why the software is giving your server trouble. There are a few routine things you can check […]

Hybrid Cloud Computing

One of the benefits of cloud computing is that you do not have to operate and maintain the applications you need on your own dedicated server. As web applications become more robust and complex, this feature of cloud computing is particularly useful to small websites and small businesses.
Hosting your own websites and applications, however, […]

To X or Not to X

On Linux, FreeBSD, and other Unix-like operating systems, the graphical interface layer is an optional separate component from the kernel and lower-level OS. Because of this, it is not necessary to have a graphical interface at all. Nevertheless, many distributions do come with the X Window System installed by default. Some may […]

How to Block IP Addresses from Your Server

As we have stressed in earlier posts at Dedicated Server School, regularly checking Linux server log files is a crucial part of server management. Knowing what is going on in your logs is a great way to detect attempts to thwart your security and come up with early prevention methods. The question you […]