Problems with loading a website are often blamed on the Internet connection, but even the most perfectly setup network cannot help if there is no service to reply at your destination. One of the most popular HTTP servers used for this task is Apache2. Much of Apache’s popularity can be attributed to its easy installation and use, but never the less it is possible to run into problems with even the easiest of the software. If you’ve encountered an issue loading your web page, follow these simple troubleshooting methods outlined in this guide to attempt to get your web server back up and working again.

Make sure the service is running

The first step to take in troubleshooting any service is to check that the service is running and able to function. A straight forward approach is to simply restart the service. On Ubuntu and Debian servers use the following command

 sudo service apache2 restart

In CentOS and other Red Hat environments Apache2 service goes by the name ‘httpd’, so use this command instead

sudo service httpd restart

Depending on your choice of distribution the output from the restart command will vary. Subjectively Ubuntu gives the most helpful reply as shown below.

* Restarting web server apache2             [ OK ]

CentOS usually just informs that the ‘service’ command has been redirected to /bin/systemctl, and Debian probably doesn’t say anything as long as the restart didn’t fail.

If your system wasn’t able to restart Apache2 you most likely got some form of an error message. In case you got a reply resembling either one of these example outputs below, the service is most likely not properly installed on your system or some files are missing.

apache2: unrecognized service
Failed to restart apache2.service: Unit apache.service failed to load: No such file or directory.

Should you see these type of errors, try installing the service again. On servers running Debian or Ubuntu use the following command

sudo apt-get install apache2

And on CentOS install httpd instead with

sudo yum install httpd

Once you are sure the web server is installed go ahead and restart the service again with the same command you used before.

If you got a different error message, try to get more information on in what kind of state your web service is in. Use one of the following commands applicable to your system.

sudo service apache2 status

sudo service httpd status

The output from the status check will tell at least whether the service is running or stopped. Debian and CentOS systems usually show more detailed report including service up time and a couple of log lines. Below is an example of a Debian status display, one on CentOS would be nearly identical. Ubuntu does not have this type of output by default.

● apache2.service - LSB: Apache2 web server
    Loaded: loaded (/etc/init.d/apache2)
    Active: active (running) since Fri 2015-07-31 10:44:26 EEST; 2h 14min ago
   Process: 9704 ExecStop=/etc/init.d/apache2 stop (code=exited, status=0/SUCCESS)
   Process: 9711 ExecStart=/etc/init.d/apache2 start (code=exited, status=0/SUCCESS)
    CGroup: /system.slice/apache2.service
            ├─9726 /usr/sbin/apache2 -k start
            ├─9730 /usr/sbin/apache2 -k start
            ├─9731 /usr/sbin/apache2 -k start
            ├─9732 /usr/sbin/apache2 -k start
            ├─9733 /usr/sbin/apache2 -k start
            ├─9734 /usr/sbin/apache2 -k start
            └─9747 /usr/sbin/apache2 -k start Jul 31 10:44:26 apache2[9711]: Starting web server: apache2.

The important part here is on the third line, active and running means the process should be working, if instead it shows active and stopped or failed, the process has most likely crashed.

Next check the processes by their name for either apache2 or httpd.

sudo ps aux | grep -E 'apache2|httpd'

For every mention of the searched keyword grep will print out a line the keyword was found on, this includes the search process itself so you will see at least the grep command. If there are more than one line of output, all but the last are processes related to your web service. An example below displays apache2 processes running on Ubuntu.

root      1457  0.0  1.5 321908 16132 ?      Ss   Jul30  0:02 /usr/sbin/apache2 -k start
www-data  1461  0.0  2.8 326532 29172 ?      S    Jul30  0:00 /usr/sbin/apache2 -k start
www-data  1462  0.0  3.1 327480 32364 ?      S    Jul30  0:00 /usr/sbin/apache2 -k start
www-data  1463  0.0  2.9 326688 30260 ?      S    Jul30  0:00 /usr/sbin/apache2 -k start
www-data  1464  0.0  3.1 326496 32148 ?      S    Jul30  0:00 /usr/sbin/apache2 -k start
www-data  1465  0.0  2.7 326816 28040 ?      S    Jul30  0:00 /usr/sbin/apache2 -k start
www-data  1841  0.0  2.0 323132 21044 ?      S    Jul30  0:00 /usr/sbin/apache2 -k start
www-data  1871  0.0  2.2 323396 23280 ?      S    Jul30  0:00 /usr/sbin/apache2 -k start
user     11669  0.0  0.0  11744   928 pts/0  S+   15:32 0:00 grep --color=auto -E apache2|httpd

Since the service restart command didn’t work earlier, any processes grep might list have probably stopped functioning and need to be closed before the service can start again. On Debian and Ubuntu systems stop all apache2 processes with

sudo killall apache2

On CentOS servers not only is the web service called something else but also the kill command functions little differently, use this instead for the same result

sudo kill -a httpd

After the kill command, you can run the process check again just to confirm that there are no more zombies left, then try to restart the service using these same commands as at the beginning of this guide.

sudo service apache2 restart

sudo service httpd restart

This should get the web service running provided that it has not been misconfigured.

Check your server configuration

When starting the service fails giving errors referring to files located in either /etc/apache2 or /etc/httpd/, the system had trouble reading the service configuration files. Apache2 comes with some handy tools for file integrity and syntax checks, that can help locating any typing mistakes or other irregularities in the configuration. With Debian and Ubuntu servers to check the config files, you can run the following command

sudo apache2ctl -t

On CentOS machines just call httpd instead with

sudo httpd -t

The output will show any problems found with the configuration file, or if everything is in order it simply prints out a confirmation like the one shown below.

Syntax OK

An other troubleshooting option for the web service is to show parsed virtual host and run settings with commands for Debian/Ubuntu and CentOS respectively

sudo apache2ctl -S

sudo httpd -S

Below is an example of the command output from CentOS system. Make sure the server and document roots point to the correct directories.

VirtualHost configuration:
ServerRoot: "/etc/httpd"
Main DocumentRoot: "/var/www/html"
Main ErrorLog: "/etc/httpd/logs/error_log"
Mutex proxy: using_defaults
Mutex authn-socache: using_defaults
Mutex default: dir="/run/httpd/" mechanism=default
Mutex mpm-accept: using_defaults
Mutex authdigest-opaque: using_defaults
Mutex proxy-balancer-shm: using_defaults
Mutex rewrite-map: using_defaults
Mutex authdigest-client: using_defaults
PidFile: "/run/httpd/"
User: name="apache" id=48
Group: name="apache" id=48

If your server uses a custom virtual host configurations, like when hosting multiple websites on one server, check that each virtual host file has the correct domain name and points to the correct root directory. On Debian and Ubuntu machines have a virtual host file by default and it is stored in /etc/apache2/sites-enabled/. Open the file for edit with

sudo nano /etc/apache2/sites-enabled/000-default.conf

This file usually has some instructions on what each parameter means in the comments, which have been left out in the example below, but the important parts are ServerName and DocumentRoot as already mentioned.

<VirtualHost *:80>
   ServerAdmin [email protected] 
   DocumentRoot /var/www/html
   #LogLevel info ssl:warn      
   ErrorLog ${APACHE_LOG_DIR}/error.log
   CustomLog ${APACHE_LOG_DIR}/access.log combined
   #Include conf-available/serve-cgi-bin.conf

CentOS and httpd do not have the same virtual host file set by default, but instead uses the httpd service configuration to store the default settings. Check the configuration file with

sudo vi /etc/httpd/conf/httpd.conf

Look for the same parameters ServerName and DocumentRoot, and make sure they are correctly set.

If you made any changes to the configuration files, the service needs to be reloaded for the changes to take an effect. Restarting the service does the job, but if you wish to avoid downtime on your web server use reload instead with one of the following commands

sudo service apache2 reload

sudo service httpd reload

Check Logs

When everything on the service side is working as expected and you cannot find a fault, but the web site just still won’t load, it’s always a good time to dig through logs. Apache2 keeps two sets of logs, access and error. You can find the logs stored at /var/log/apache2/ or /var/log/httpd depending on your choice of Linux distribution. You can list all files in your web service’s log directory with

sudo ls /var/log/apache2/

sudo ls /var/log/httpd/

The log lists will differ slightly as different systems name the logs a little differently. Ubuntu and Debian servers store the current uptime logs to access.log or error.log, previous logs are marked with a running number, 1 being the latest, and older logs than that are also compressed. On CentOS and other Red Hat variants the logs are named access_log and error_log, older logs have their name appended with the date the log was written on e.g. access_log-20150108.

An easy way to start reading the logs, when you don’t necessary know what you are looking for, is to use the filtering app ‘grep’. Search for any errors using the one of commands below which corresponds with your system’s web application name.

sudo grep -i -r error /var/log/apache2/

sudo grep -i -r error /var/log/httpd/

Ubuntu and Debian users might also need to check through the compressed log files. This can be done using ‘zgrep’ instead, but due to its limitations you can only search one log at the time, for example using this following command

sudo zgrep error /var/log/apache2/error.log.2.gz

Not all errors logged by your web service necessarily mean there is something wrong with your server, but keep an eye out for any repeating problems like missing files in the example error below

[Fri Jul 17 12:36:08.431065 2015] [:error] [pid 4649] [client] script '/var/www/html/index.php' not found or unable to start

You may also wish to enable more verbose logging if searching for errors is not yielding much results. The log output amount is controlled by a parameter called ‘LogLevel’ in the web service’s configuration file. On Debian and Ubuntu systems, open your configuration file with

sudo nano /etc/apache2/apache2.conf

With CentOS and other Red Hat based server use the command here instead

sudo vi /etc/httpd/conf/httpd.conf

Find the LogLevel parameter and change it from the default ‘warn’ value to ‘debug’ instead, then save the file and exit. Again for any changes to be applied, the service needs to be reloaded. You can do this with one of the following commands appropriate for your system

sudo service apache2 reload

sudo service httpd reload

To generate some new entries using the new log levels, try to access your web site again a couple of times even if it doesn’t work. The more verbose logs should help with narrowing down any underlying issues.

Check other services

If your website still won’t load after all the troubleshooting with Apache, check other related service on your cloud server such as database, firewall and network connection, which also have their own troubleshooting instructions.

Do not hesitate to contact UpCloud Support, please follow the instructions in your UpCloud Control Panel, under My Account and Support –tab. Remember to include any relevant information you may have discovered while troubleshooting, as every bit of detail will be useful in further investigation.