Clear QPID Queues and delete them

1. Connect to Qpid:
    # qpid-tool

2.  List the Queues:
   qpid:  list queue
 
     Object Summary:
    ID   Created   Destroyed  Index
    ===============================================================
    154  02:05:42  -          175.ax-q-myqueue2
    155  07:14:00  -          175.ax-q-myqueue1
    156  07:15:36  -          175.ax-q-myqueue1-dl


3. To delete the Queue use the below command:
    qpid: call 154 purge 0 {}
    qpid: OK (0) - {}

    Here, '154' is the ID of the Queue.

4. Press Ctrl + c to come out of QPID terminal.

5. Run the below command to see if the Messages are cleared:
    # qpid-stat -q

Queues
  queue                            dur  autoDel  excl  msg   msgIn  msgOut  bytes  bytesIn  bytesOut  cons  bind
  ================================================================================================================
  ax-q-solar-myqueue1-dl          Y                      0   589    589       0    553k     553k        0     2
  ax-q-solar-myqueue1           Y                      0   589    589       0    553k     553k        0     2
  ax-q-myqueue2                     Y                      0   330    330       0    250k     250k        0     2


6. Delete the Queue using the below command:
   #  qpid-config del queue ax-q-solar-myqueue1

    Here 'ax-q-solar-myqueue1' is the queue name.

No Java Found Issue

Recently, we faced the 'no Java' issue while trying to run a server using the init scripts.

The error we saw was:

which: no java in (/sbin:/usr/sbin:/bin:/usr/bin)

We already has JAVA_HOME configured in the bashrc file. But the init script was looking for it elsewhere.

Below are the steps we can do to fix this issue:

1. Run the echo command to check the JAVA_HOME path

     echo $JAVA_HOME

     /usr/java/jdk1.7.0_51/       ---> This is the JAVA_HOME Path in my machine.

2. Run the which command to locate the program.

    which java

     /usr/java/jdk1.7.0_51/bin/java

3. Create a symlink to this location in '/usr/bin/' for this case as it is one of the location the init script looks for java.

    ln -s /usr/java/jdk1.7.0_51/bin/java /usr/bin/java

  

Try to run the Server again. 

    

    

Setting up SSH Keys

There are many blogs about creating keys and SSHing into the machines. I have written this one as i often get confused about the location of keys and the machines on which it should be generated. (Yeah! I know. I am forgetful!)

Machine Names:  Machine1 and Machine2.
Problem Statement: We should be able to log in from Machine1 to Machine2 without using password.

Steps to Enable SSH login between Machine1 and Machine2:

1. Log into Machine1.

2. Go to ~/.ssh folder. If this folder does not exist then create one using the below command in both the machines:
    mkdir ~/.ssh/
    mkdir ~/.ssh/authorized_keys

    chmod 700 ~/.ssh

    chmod 600 ~/.ssh/authorized_keys

3. Go to the ~/.ssh folder and generate the Key pair:
    ssh-keygen -t rsa

4. Once you enter the above command, the next question that will come up is:
    Enter file in which to save the key (/Users/deepti/.ssh/id_rsa):

5. Provide a name for the keys. In my case, the name was 'mykeys'.

6. The next question that will come up is:
     Enter passphrase (empty for no passphrase):
       
        It is your choice whether you want to use a passphrase. In case, you are using automated scripts to SSH between the machines then its better to leave it empty. In order to leave it empty just hit the 'Enter/Return' key.

7. The below lines will be printed once you are done with the above steps:

     Your identification has been saved in mykeys.
Your public key has been saved in mykeys.pub.
The key fingerprint is:
fe:3c:f4:6a:06:c8:3a:17:98:67:b8:1a:01:66:da:28 deepti@Deeptis-MacBook-Pro-5.local
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|                 |
|.o               |
|++               |
|E o  = .S        |
|.  .+ *.. .      |
|  .  = ..o .     |
|   .+ .  o+ .    |
|  .. o   o+o     |
+-----------------+

8. Here your key generation process has been completed.

9. Open the mykeys.pub file. Replace the machine name with the IP of the Machine1.

Before replacing:  root@Deeptis-MacBook-Pro-5.local
After replacing: root@192.168.1.105

10. Copy the contents of mykeys.pub file to 'authorized_file' of Machine2 using the below command:
cat ~/.ssh/id_rsa.pub | ssh root@192.168.1.115 "cat >> ~/.ssh/authorized_keys"

Here, 192.168.1.115 is the IP of Machine2.

11. Now you are ready to go. Try to login from Machine1 to Machine2 without using password:

ssh root@192.168.1.115    #Machine2's IP

You should not be prompted for a password. However, if you have set a passphrase, then the system will prompt you for it.

Changing the Timezone of PostGreSQL DB

Steps to change the Timezone of PostGres DB are:

1. Log into the Machine which has the PostGres DB.

2. Log into the DB:
    psql -U postgres -d <db_name>

3. Check the time zone of the DB using the below command:
    # show timezone;

4. Log out from the DB.
 
5. Switch to postgres user:
    su - postgres

6. Open the 'postgresql.conf' file in edit mode. This file is usually located inside 'pgdata' folder. Search for the string 'timezone'. Change the value of 'timezone' as desired. The valid timezone values are listed at this link. In this case, we have changed the timezone value to 'Europe/London'.

#intervalstyle = 'postgres'

timezone = 'Europe/London'

7. Save the file.

8. Restart the PG DB. The commands I used are listed below. It depends on the location of the installation.

To Stop:

/usr/pgsql-9.3/bin/pg_ctl -D /ebs/pgdata/ -m fast stop

To Start:

/usr/pgsql-9.3/bin/pg_ctl -D /ebs/pgdata/ -l logfile start

9. Log into the DB again. And check the Timezone:

    #show timezone;

     TimeZone

     ---------------

     Europe/London