How to reset Mac OS iCal - Apple Calendar

Due to migrating and upgrading on mac os since some time I was facing calendar issues:
- "The URL https://<...>/ encountered HTTP error 302. Make sure the URL is correct."
- some calender subscriptions disappeared. I could not create subscriptions: "... this calender exists."

Important to mention: I had no local calender entries!

So I wanted to reset my iCal in Mac OS.

The following is a description, how I have done this.
No garantee!

MAC OS X Yosemite Version 10.10.2 - MacBook Pro - iCal Version 8.0 (2021.6.1)

1. Take a note of your calender seetings
    - open system settings - internet accounts
    - make a note or screenshot of your settings. You need it later, when you setup.
    - in calender do a right click on calender subscriptions and make note of the URLs

2. Disconnect all your attached devices
    - disconnect mouse, keyboard, disk drives etc.

3. Disconnect from Network
    - disconnect network cable
    - disable WI-FI
 
4. Close all Applications and Reboot

5. Close all applications started due to autostart operations

6. Remove calender account
    - open system settings - internet accounts
    - remove the calender account

7. Remove Caches and Calender data
    - open a finder
    - from the menue select "connect to folder":
       /Volumes//Users//Library
      where is the name of your disk, ans is your user.


    Important! Do not delete anything. Simply move the following folders to a new location
    (for example your desktop) to have a backup!

    - in the above mentioned folder ".../Library" move the following folders to the backup location:
      1. Caches
      2. Calendars
    - check the folder are no longer under ".../Library".
    - now goto folder   ".../Library/Containers" and move the following files to your backup location:
      3. com.apple.CalendarAgent
      4. com.apple.iCal
    - check the files are no longer under ".../Library/Containers".

8. Reboot again

9. Open iCal
    iCal should be reset to defaults.
    Re-create your iCal account and subscriptions.

10. Your calender should be fresh and fast.
      Remember to clean up your backed-up folders.

Configure Firefox Java Browser plugin

Although Java might be installed on your Oracle Linux system, your browser might not know Java.
So, this is how to get your firefox up to speed.

1. Identify Java Install locations (Remember this document - No. 7)

Become User "root":

$ su -Password:
# 

Query the standard java directory on Oracle Linux:

# ls -l /usr/java/
total 8
lrwxrwxrwx. 1 root root   16 Jan  9 13:24 default -> /usr/java/latest
drwxr-xr-x. 8 root root 4096 Jan  9 13:49 jdk1.7.0_71
drwxr-xr-x. 9 root root 4096 Jan  9 13:40 jdk1.8.0_25
lrwxrwxrwx. 1 root root   21 Jan  9 13:40 latest -> /usr/java/jdk1.8.0_25

2. Find Mozilla Firefox Plugin Directory

2.1 Check your browser binary version
This is important, where to find the library!
(Firefox must be running.)

# ps -ef|grep firefox
root     12536 28294  0 14:53 pts/4    00:00:00 grep firefox
oracle   13105     1  6 11:51 ?        00:11:57 /usr/lib64/firefox/firefox

Mine is 64bit, so I have to use the 64bit plugin.

2.2 Navigate to standard Mozilla plugin directory

# cd /usr/lib64/mozilla/plugins

3. Check for existing symbolic links to the mozilla plugin

First check, if there is a link to the libnpjp2.so file:

# ls
libflashplayer.so  libtotem-cone-plugin.so  libtotem-mully-plugin.so
libnpjp2.so        libtotem-gmp-plugin.so   libtotem-narrowspace-plugin.so

4. Close your Firefox Browser!


5 Remove existing symbolic link

rm libnpjp2.so
rm: remove symbolic link `libnpjp2.so'? y

6 Create new symbolic link

# ln -s /usr/java/jdk1.7.0_71/jre/lib/amd64/libnpjp2.so

7 Test your Java Browser Plugin

Open Firefox and open Java Test Page:
https://www.java.com/en/download/help/testvm.xml
The output should be similar to mine:

Verified Java Version

Congratulations!

You have the recommended Java installed (Version 7 Update 71).

How To Install and manage Java JDK on Oracle Linux

Every Time I set up an Oracle Linux server, I ask myself, how have I done it last time ...

1. Check which Java Version (JDK7, JDK8, ...) is certified with your software.
e.g. Oracle Fusion Middleware supported system configurations:
http://www.oracle.com/technology/software/products/ias/files/fusion_certification.html

2. Check support policy, esp. end of life for your desired Java Version
http://www.oracle.com/technetwork/java/javase/downloads/eol-135779.html

3. Download JDK
http://www.oracle.com/technetwork/java/javase/downloads/index.html

4. Install JDK

# ls -l jdk*
-rw-r--r--. 1 oracle oinstall 126679286 Jan  9 13:01 jdk-7u71-linux-x64.rpm
-rw-r--r--. 1 oracle oinstall 142191827 Jan  9 13:06 jdk-8u25-linux-x64.rpm

# rpm -Uhv jdk-7u71-linux-x64.rpm
Preparing...                ########################################### [100%]
   1:jdk                    ########################################### [100%]
Unpacking JAR files...
    rt.jar...
    jsse.jar...
    charsets.jar...
    tools.jar...
    localedata.jar...
    jfxrt.jar...

5. Check Java Version

# java -version
java version "1.7.0_71"
Java(TM) SE Runtime Environment (build 1.7.0_71-b14)
Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode)

If this is your expected Java Version - fine! Your are done!
If you still have a pointer to an older version, move on ...

...

6. A non expected Java Version is present?     lets say, JDK8 is still present, but you need to move back to JDK7

# java -version
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)

7. Check Java install locations

# ls -l /usr/java/
total 8
lrwxrwxrwx. 1 root root   16 Jan  9 13:24 default -> /usr/java/latest
drwxr-xr-x. 8 root root 4096 Jan  9 13:49 jdk1.7.0_71
drwxr-xr-x. 9 root root 4096 Jan  9 13:40 jdk1.8.0_25
lrwxrwxrwx. 1 root root   21 Jan  9 13:40 latest -> /usr/java/jdk1.8.0_25

8. Make use of alternatives system to switch between versions

8.1 Syntax of alternatives

# /usr/sbin/alternatives
alternatives version 1.3.49.3 - Copyright (C) 2001 Red Hat, Inc.
This may be freely redistributed under the terms of the GNU Public License.

usage: alternatives --install
                    [--initscript ]
                    [--slave ]*
       alternatives --remove
       alternatives --auto
       alternatives --config
       alternatives --display
       alternatives --set

common options: --verbose --test --help --usage --version
                --altdir --admindir

8.2 Register your JDKs for alternatives

usage: alternatives --install

# /usr/sbin/alternatives --install /usr/bin/java java /usr/java/jdk1.7.0_71/bin/java 17071

(where priority represents 17071 for jdk1.7.0_71)

# /usr/sbin/alternatives --install /usr/bin/java java /usr/java/jdk1.8.0_25/bin/java 18025

(where priority represents 18025 for jdk1.8.0_25)

8.3 Now to switch between the versions

8.3.1 Check current java version, again

# java -version
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)

8.3.2 Change the current java version

 # /usr/sbin/alternatives --config java

There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
   1           /usr/java/jdk1.7.0_71/bin/java
*+ 2           /usr/java/jdk1.8.0_25/bin/java

Enter to keep the current selection[+], or type selection number: 1

8.3.3 Check your current java version has changed

# java -version
java version "1.7.0_71"
Java(TM) SE Runtime Environment (build 1.7.0_71-b14)
Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode)

9. Keep your path JDK dynamic

The idea is, when you install for example WebLogic Server, to use a dynamic location to your JDK.
I do this with a symbolic link.
I have a folder /opt/oracle/java where I create a symbolic link, that points to the jdk.
As normal user I create the symbolic link:

$ ln -s /usr/java/jdk1.8.0_25 /opt/oracle/java/java

When an updated jdk version in available, after install I only change the symbolic link:

$ rm /opt/oracle/java/java
$ ln -s /usr/java/jdk1.8.0_31 /opt/oracle/java/java

For the WebLogic Server, the path to java will remain. No reconfiguration is needed.
So I only have to restart the WebLogic Server to use the latest JDK.

10. Tidy up! - delete out of date JDKs

10.1 Remove rpm

To delete the out-of-date versions of the JDK:
Query for all installed JDK rpms:
# rpm -aq | grep -i jdk
jdk1.8.0_31-1.8.0_31-fcs.x86_64
jdk-1.7.0_85-fcs.x86_64
jdk1.8.0_60-1.8.0_60-fcs.x86_64

In this example, I need to remove the jdk1.8.0_31:
# rpm -e jdk1.8.0_31-1.8.0_31-fcs

Check that the rpm has been deleted:
# rpm -aq | grep -i jdk
jdk-1.7.0_85-fcs.x86_64
jdk1.8.0_60-1.8.0_60-fcs.x86_64

10.2 De-register the java alternatives entry

Now we need to de-register the jdk in the alternatives configuration:
Current alternatives configuration:
# /usr/sbin/alternatives --config java

There are 3 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
   1           /usr/java/jdk1.7.0_75/bin/java
   2           /usr/java/jdk1.8.0_31/bin/java
*+ 3           /usr/java/jdk1.8.0_60/jre/bin/java

We need to remove selection No 2:
# alternatives --remove java /usr/java/jdk1.8.0_31/bin/java

Check again:
# /usr/sbin/alternatives --config java

There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
   1           /usr/java/jdk1.7.0_75/bin/java
*+ 2           /usr/java/jdk1.8.0_60/jre/bin/java

Enter to keep the current selection[+], or type selection number: 2


Voilà!