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2024

  • in Apache
  • 1 min read

How to check all the apache httpd processes in Linux

When we want to find a list of processes running on a Linux box, we use.

ps -fax
Now apply the grep command to filter out only httpd process list.

ps -fax | grep httpd

or

ps -ef | grep httpd

To know the number of httpd processes running apply ‘wc -l’ command like

ps -fax | grep httpd | wc -l
ps -ef | grep httpd | wc -l

[Fixed] Unsigned application requesting unrestricted access to system

Subject/ Problem Description

The following error is displayed when launching applications signed with the MD5withRSA or MD5withDSA algorithms after upgrading to Java.

Unable to launch the application.
Unsigned application requesting unrestricted access to system
Unsigned application requesting unrestricted access to system. 
The following resource is signed with a weak signature algorithm MD5withRSA 
and is treated as unsigned: http://example.net/ExampleApplication.jar
Symptoms / Root Cause:

Applications signed with the MD5withRSA or MD5withDSA algorithms are treated as unsigned by Java starting with the Java 8 Update 131 release.

  • in DevOps
  • 1 min read

java vs javaw vs javaws

java: Java application executor which is associated with a console to display output/errors

javaw: (Java windowed) application executor not associated with console. So no display of output/errors. It can be used to silently push the output/errors to text files. It is mostly used to launch GUI-based applications.

javaws: (Java web start) to download and run the distributed web applications. Again, no console is associated.

All are part of JRE and use the same JVM.

Difference between java, javaw, javaws and javac

https://javapapers.com/core-java/java-vs-javaw-vs-javaws/

What is the difference between 'java', 'javaw', and 'javaws'?

  • in DevOps
  • 1 min read

JDK VS JRE VS JVM

JDK is the development platform, while JRE is for execution. JVM is the foundation, or the heart of the Java programming language, and ensures the program's Java source code will be platform-agnostic. JVM is included in both JDK and JRE—Java programs won't run without it.

  • in Linux
  • 1 min read

How to set semaphore limits

In some scenario, the application had a semaphore limit issue. We need to increase some semaphore limits, such as semaphore array.

How do we set the semaphore limits?

What values should we set for the semaphore limits? 

# ipcs -ls

------ Semaphore Limits --------
max number of arrays = 1024              ## SEMMNI
max semaphores per array = 250           ## SEMMSL
max semaphores system wide = 256000      ## SEMMNS
max ops per semop call = 32              ## SEMOPM
semaphore max value = 32767

What is -h vs --help in Linux command?

-h vs --help

To sum up, the Linux shell provides access to help information for commands through both -h and —help.

However, —help is a more uniform and universal option that may be used with a variety of commands. Shorter and occasionally used, -h can have varying availability and significance.

It is advised to use --help to reliably obtain help information, particularly for commands that are unknown.

  • 1 min read

Forward slash vs Backslash

Backslash (Windows) and Forward Slash (Linux)

The documentation uses backslashes ( \ ) for Windows and forward slashes ( / ) for Linux environments. When the documentation mentions a backslash, the forward slash implicitly applies to Linux.

Linux vs Windows Commands

SNo. Windows Linux Description
1. dir ls -l Directory listing
2. ren mv Rename a file
3. copy cp Copying a file
4. move mv Moving a file
5. cls clear Clear Screen
6. del rm Delete file
7. fc diff Compare contents of files
8. find grep Search for a string in a file
9. command /? man command Display the manual/help details of the command
10. chdir pwd Returns your current directory location
11. time date Displays the time
12. cd cd Change the current directory
13. md mkdir To create a new directory/folder
14. echo echo To print something on the screen
15. edit vim(depends on editor) To write in to files.
16. exit exit To leave the terminal/command window.
17. format mke2fs or mformat To format a drive/partition.
18. free mem To display free space.
19. rmdir rm -rf/rmdir To delete a directory.
20. taskkill kill To kill a task.
21. tasklist ps x To list running tasks.
22. set var=value export var=value To set environment variables.
23. attrib chown/chmod To change file permissions.
24. tracert traceroute To print the route packets trace to network host.
25. at cron daemon to execute scheduled commands.
26. type cat To print contents of a file.
27. ping ping To send ICMP ECHO_REQUEST to network hosts.
28. nslookup nslookup To query Internet name servers interactively.
29. chdisk du -s For disk usage.
30. tree ls -R To list directory recursively.