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Linux

Clear the Java Web Start (javaws) cache

  1. Open your computer's DOS prompt by selecting the Start menu followed by the Run option. Then, enter command followed by pressing the Enter key.

  2. Type javaws at the DOS prompt followed by the Enter key to see the Java Web Start command-line options.

  3. Type javaws -Xclearcache followed by the Enter key to clear Java Web Start Cache on your computer. After the cache has been cleared, the local drive prompt will appear on the DOS prompt.

This will be the command to clear cache

// Remove all non-installed applications from the cache.
javaws -clearcache 

// Remove all applications from the cache
javaws -uninstall

Alternatively, do the following:

  1. Delete the cache folder located on Windows 
    "C:\Users\<user>\AppData\LocalLow\Sun\Java\Deployment"
  2. For other Operating System versions, you might have to do the delete operation in the appropriate Sun Java folder.

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You can do it using Java Control Panel

How do I clear the Java cache?

How can do it in command line?

  • 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.

Linux vs Windows Commands

SNo.WindowsLinuxDescription
1.dirls -lDirectory listing
2.renmvRename a file
3.copycpCopying a file
4.movemvMoving a file
5.clsclearClear Screen
6.delrmDelete file
7.fcdiffCompare contents of files
8.findgrepSearch for a string in a file
9.command /?man commandDisplay the manual/help details of the command
10.chdirpwdReturns your current directory location
11.timedateDisplays the time
12.cdcdChange the current directory
13.mdmkdirTo create a new directory/folder
14.echoechoTo print something on the screen
15.editvim(depends on editor)To write in to files.
16.exitexitTo leave the terminal/command window.
17.formatmke2fs or mformatTo format a drive/partition.
18.freememTo display free space.
19.rmdirrm -rf/rmdirTo delete a directory.
20.taskkillkillTo kill a task.
21.tasklistps xTo list running tasks.
22.set var=valueexport var=valueTo set environment variables.
23.attribchown/chmodTo change file permissions.
24.tracerttracerouteTo print the route packets trace to network host.
25.atcrondaemon to execute scheduled commands.
26.typecatTo print contents of a file.
27.pingpingTo send ICMP ECHO_REQUEST to network hosts.
28.nslookupnslookupTo query Internet name servers interactively.
29.chdiskdu -sFor disk usage.
30.treels -RTo list directory recursively.