Explore information related to 500 internal server error in apache


Apache Error: "semget: No space left on device" - Fix it Now ?


This article covers methods to resolve Apache Error: "semget: No space left on device". This error indicates that apache failed and will not start again, so check the error log If you see an error similar to the following, it could indicate that your server has run out of semaphores and apache cannot be started:

[emerg] (12)Cannot allocate memory: mod_fcgid: Create process manager error
[error] (28)No space left on device: Cannot create SSLMutex Configuration Failed


To solve this problem you can restart Apache, Postgres and other services that consumer many IPC resources or increase limit of the resources in the system using 'sysctl'. When you stop all services the semaphores and shared memory segments have to be removed, if not, and you still able to see them using 'ipcs' command, try to remove them manually using 'ipcrm' command. 

1. For example to remove semaphore:

# ipcs -a

2. If this is a common problem for you, you may want to increase the semaphore limits on your VPS server. You can do that by adding the following to the /etc/sysctl.conf file:

# Increases the semaphore limits & extend Apache's uptime.

kernel.msgmni = 512
kernel.sem = 250 128000 32 512

3. Then load the new settings into the kernel:

sysctl -p

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Apache Maven on Ubuntu Steps to install it


This article will guide you on how to #install #Apache #Maven on Ubuntu. Basically, Apache Maven is a popular build management tool for #Java projects. 

To test The Maven Installation in #Ubuntu:

Run the command mvn -version to check if the maven is installed properly. 

You will see the below description on the command prompt. Maven is installed successfully.

Some Maven #Commands:

1. mvn clean. This command cleans the maven project by deleting the target directory. 

2. mvn compiler:compile. This command compiles the java source classes of the maven project. 

3. mvn compiler:testCompile. 

4. mvn package. 

5. mvn install. 

6. mvn deploy. 

7. mvn validate. 

8. mvn dependency:tree.

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Steps To Install Spark On Ubuntu


This article will guide you on how to install #Apache spark on a single #Ubuntu system. Apache Spark is a distributed open-source, general-purpose framework used in cluster computing environments for analyzing big data. You will be able to perform basic tests before you start configuring a #Spark cluster and performing advanced actions.

Spark is not a #database so it cannot "store data". It processes #data and stores it temporarily in memory, but that's not presistent storage. It can access data that's in: #SQL Databases (Anything that can be connected using JDBC #driver).

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