There are a hundred and one thousand things that can go wrong with any web server installation. From a fresh installation to an installation that has been running for a long time, you never know when something is going to cause your web server to go astray. When it does happen, it’s always nice to know that, usually, Occam’s Razor applies.

In this tutorial you will find some advice that will help you through some of the more common issues that can pop up with an Apache web server.

Is your server actually running?

Believe it or not, this has happened to plenty of administrators. You take the server down, do some maintenance, and when you go to check out the server you’re getting errors. The first thing you do, naturally, is check out that /etc/apache2/apache.conf file to make sure your syntax is correct. But it’s perfect! What’s up? The first thing you might want to check is to make sure the server is running. But you don’t want to just issue the command to start the server or reload the server. Instead, issue the command:

sudo /etc/init.d/apache2 status

Which should return something like:

* apache is running (pid 9751).

If not, start the server with either:

sudo /etc/init.d/apache2 start

or

sudo apache2ctl start

NOTE: If you are using a distribution like Fedora, SuSE, or Mandriva you will need to first su to the root user and issue the above commands WITHOUT using sudo.

It’s not running and it won’t start

Did you just make changes to your Apache configuration file? Are the changes correct? If you’re not sure, you can use the apache2ctl command to check the syntax of your configuration file. This is done with the command:

sudo apache2ctl configtext

The above command should report:

Syntax OK

If you don’t get an OK, you will get information that points to the errors in your configuration file.

Apache wants to download .php files!

This is another common issue. When you add a new tool on your web server (such as Drupal), if your configuration file is set up properly, any .php file might not be displayed. Instead any attempt to view a .php file will instead have your browser trying to download the file. Why is this? Apache must be informed that certain extensions are to be displayed, not downloaded. This is done from within the Apache configuration file. Open up that file (in the Ubuntu server it will be /etc/apache2/apache2.conf) and first look for the following line:

DirectoryIndex index.html

If that file doesn’t include index.php nearly all sites that use php will be rendered useless.

The second line to look for is:

AddHandler application/x-httpd-php .php

If you find this line, and it is commented out, make sure you uncomment it by removing the “#” character. If it is not there add it to the bottom of the configuration file.

And, as always, when you make a change to the configuration file, restart Apache.

Know where to look for problems

Finally, it is crucial that you know where to first turn when the above doesn’t help you out. Any time I have an issue with Apache where Occam’s Razor does not apply, the first place I turn is the log files.

If you look in /var/log/apache2 you will find, at least, the following files:

• access.log: This keeps track of any connection made to your server.
• error.log: This keeps track of any errors that occur with Apache.
• other_vhosts_access.log: This is where virtual hosts will log when the virtual host has not been prescribed its own log file.

Of course, as your site evolves so will your available log files. Regardless of what you find in /var/log/apache2, that is where you should always first turn when you have problems. Even before you google.

Final thoughts

Now you should be able to handle some of the more common issues with the Apache server. And if your problem isn’t common, you also know where to turn to find clues that will lead you down the right path to correction.

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It is possible to load multiple log files into the log viewer which can then be looked at and switched to in the tabbed interface on top of the application. Log Viewer Pro will automatically highlight lines that contain warnings, information or errors to make the identification easier for the user. It is possible to define additional lines that get highlighted automatically using regular expressions.

The application can switch to different encodings like ANSI, OEM, Unicode LE, Unicode BE, supports line numbers, text wrapping and a search that supports basic search phrases but also regular expressions. The log files can be automatically reloaded if that is required. Another interesting feature are bookmarks which can be created to jump to specific locations in a log file.

Log Viewer Pro is a free for non commercial use log analyzer for the Windows operating system.

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Multitail does exactly as it sounds – it allows more than one instance of the tail command in a single window. Given that we should probably take a look at the tail command first.

Tail

What tail does is print the output of a log file in real time. With this you can open up, say, /var/log/messages with tail and see the last ten lines of that file as they are printed.  This comes in very handy when you need to see the errors precisely as they happen.

To run the tail command on a log file (we’ll stick with our example above) you would issue the command:

tail -f /var/log/messages

You would see printed the last ten kernel buffer messages as they are added. This is very helfpul when you are plugging in a USB device and you want to find out what address the device is attached to.

But what if you want to view, say, /var/log/mail.err and /var/log/mail.warn together? Sure you could open up two terminals and issue the tail commands for each log file, but why do that when you can have them in the same window?

Getting and installing multitail

The easiest way to install multitail is to issue the command (since you’ll be working in the command line anyway):

sudo apt-get install multitail

or

yum install multitail

Once the application is installed you are ready to go (there is no configuration necessary).

Running multitail

The structure of the multitail command is:

multitail -i FIRSTLOG -i SECONDLOG

Where FIRSTLOG and SECONDLOG are the log files you want to follow. Sticking with the example above let’s follow mail.err and mail.info. We do this with the command:

sudo multitail -i /var/log/mail.err -i /var/log/mail.info

Figure 1

The above command will have multitail following both log files horizontally (as shown in Figure 1). At first it can be a bit disconcerting to see and follow. What you are seeing is the /var/log/mail.err file being tail’d on top and the /var/log/mail.info file being tail’d on bottom. The easiest way to discern one from the other is at the bottom of each tail is the white bar showing what file is being tail’d.

If you do not like the horizontal layout you can change that to a vertical layout with the s switch like so:

sudo multitail -s 2 -i /var/log/mail.err -i /var/log/mail.info

Figure 2

When you run this version of the command the tail’s are side by side with a wide vertical bar between them (as you can see in Figure 2).

Merging logs

You can also use multitail to merge multiple logs into one log. This can help you when you know you need to follow the output of more than one log file but you don’t need them separated. To do this you use the mergeall option like so:

sudo multitail –mergeall -i /var/log/mail.err -i /var/log/mail.info

Final thoughts

Multitail is one of those tools that once you get used to having it in your toolkit you will pull it out again and again.

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Log Viewer is a simple GUI tool that houses all your log files in one convenient location with a point and click interface and a user-friendly calendar that helps you navigate through dates.

Fire It Up

Starting Log View is simple. Go to the Applications menu and click the System Tools sub menu. Within the System Tools sub menu you will see the System Log entry which, when clicked, will ask for your root password. After you enter the root password the Log Viewer application will start.

Log Viewer

When you first open Log Viewer it will most likely default to the Xorg.0.log file. You will have access to any of the log files within the the /var/log directory. And any of those logs that have dated entries will allow you to click through the calendar to view other dates of your log file. If the log file you are viewing does not have dated entries (or archived entries) the calendar will be grayed out.

To view archived logs you will click the Version dropdown which will reveal how ever many versions (or archives) of the particular log file you are viewing.  For instance if I click on the Xorg.0.log file I have the current entry and one other archive. If I click on the messages log file I will see the current entry as well as archives 1 – 4.

You can also add a filter to your viewing. This will be very helpful when you are troubleshooting. Say, for example, you are trying to track down a particular rogue IP address within the secure log. Click the Ctrl-f combination to open the Filter text box and enter the IP address when viewing the secure log file. If the IP address you are searcing for is in the log file, any entry containing that IP address will show up in the viewing area.

Final Thoughts

I am a frequent viewer of log files. Any time I am troubleshooting the /var/log directory is the first place I turn. But sometimes searching for a needle in a haystack can require more time than I have. With the help of Log Viewer this task is made much easier.

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dmesg

When I have a problem (or when I am attaching a usb device) one of the first places I go is the dmesg command. The dmesg command prints out the kernel keyring buffer. The information you will get will be all of the information you do not see when your system is booting. This is a great place to get information (low level) on your hardware. On one of my laptops, I run dmesg and near the top I see:

Phoenix BIOS detected: BIOS may corrupt low RAM, working it around.
last_pfn = 0x7f6d0 max_arch_pfn = 0x100000
x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106
kernel direct mapping tables up to 38000000 @ 10000-15000
Using x86 segment limits to approximate NX protection
RAMDISK: 37c6a000 - 37fef4a2


From that I can tell I have a Phoenix bios. Pretty obvious. A little later I see:

Security Framework initialized
SELinux:  Initializing.
SELinux:  Starting in permissive mode

Now I know Security Enhanced Linux is starting, in permissive mode, at bootup. And even further on down the line I see:

CPU1: Intel(R) Pentium(R) Dual  CPU  T2390  @ 1.86GHz stepping 0d
checking TSC synchronization [CPU#0 -> CPU#1]: passed.
Brought up 2 CPUs
Total of 2 processors activated (7447.76 BogoMIPS)

The above shows me information about my CPU. Good to know.

The most important information you will probably get from dmesg is the information regarding attached USB devices. When you plug in a USB device you will need to know what special device this is attached to so you can mount it. This will occur at the bottom of the dmesg command output.

The output of dmesg is quite long and will scroll by very quickly. When I run this command I always pipe it through the less command like so:

dmesg | less

This way I can view the output one page at a time.

/var/log

This special directory is the Mac Daddy of information gathering. Fire up a terminal window and issue the command ls /var/log/ and see what it contains. You see, included in this listing, such log files and log directories as:

• boot.log – boot information
• cron – cron logs
• cups – directory of all printing logs
• httpd – Apache logs
• mail – Mail server logs
• maillog – The mail log
• messages – Post-boot kernel information
• secure – Security log
• Xorg.0.log – X Server log

You can see the listing of log files in the /var/log directory, but in order to actually read the log files you have to be the root user (or use sudo).

Viewing with tail

One of the handiest methods of viewing log files is using the tail command. What tail does is follow the running output of a log file. For instance if I want to follow my /var/log/secure log to watch for security issues I would enter the command tail -f /var/log/secure. The f switch tells tail to follow. If  you don’t add the f switch tail will just list the output all at once (as if you just issued less /var/log/secure.)

Final Thougths

There is so much information to be gained from reading log files. The Linux operating system makes reading log files easy, once you know which log file does what. Take a poke around /var/log to find out exactly what you have and where you need to look for the problem you are having.

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This log files can become huge if you have a popular website. The current size of the Ghacks log file is 45 Gigabytes. If it continues growing in that pace the web server will run out of hard disk space pretty soon.

The first problem was to figure out how to backup the 45 Gigabyte file on the web server since I did not want to loose all the data stored within. The idea was born to compress the Apache web server log file first and then reduce it to a few Kilobytes with the echo command.

The Apache web server log files are stored in the /var/log/apache2 directory on the Debian dedicated server. The first command to issue would compress the contents of the apache2 directory into multiple tar files if the compressed file reaches a size maximum. This makes it easier to transfer files to another computer.

tar -cz directory | split -d -b 1024m - destination.tgz

Directory is the source directory where the Apache web server log files reside and destination.tgz is the name of the to be created compressed file. It is important to note that you might need to stop the Apache web server for the operation to succeed because the compression utility will stop if files get changed during procession.

The last thing that is to be done is to clear the original Apache web server log files in the log files directory. This can be done with the following command even if Apache is running.

echo " " > /var/log/apache2/filename.log

This simply overwrites the contents of the file. Please note again that some Linux distributions use another directory structure and that the log files can be located in another directory on the server.
This takes only a few seconds and the log file will be cleared from all contents afterwards.

Then it is just a matter of transferring the various compressed archives to another computer.

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Txt Collector comes with some options to make the life of the user a bit easier. It may grab all text files from one directory plus all subdirectories if desired and combine them on the fly which is great if you want to merge many text files.

It is furthermore possible to add separators after each text file to see the end and the beginning of new text files visually. Txt Collector supports all Microsoft operating systems starting with Windows 95 up to Windows Vista.

Read More:

Txt Collector

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