Technical Articles: May 2012

HOWTO: Change your default user account to a system account

When you deploy a new Ubuntu installation, the first user it creates (uid=1000) will be given sudo privileges. Sometimes it is desirable to have a specific "admin" user on your system that is separate from your normal user accounts which are located in the uid=1000+ range. For example, if you are setting up an LDAP network. Unfortunately, you can't set the uid manually during the initial installation process but you can change it afterwards.

Note:
If you make a mistake during this procedure it is possible to lock yourself out of the system completely. This is not such an issue if this is a freshly installed system but if it is already up and running in some sort of role, then you need to be extra careful. You have been warned!

I am working here with a fresh Lucid server install, and my uid=1000 user is called "sysadmin".

Login to a console session as root;

~$ sudo -i

Manually edit your passwd file;

~# vi /etc/passwd

At the end of the file will be the entry for the "sysadmin" account;

sysadmin:x:1000:1000:system admin,,,:/home/sysadmin:/bin/bash

Change the two "1000"'s to "999";

sysadmin:x:999:999:system admin,,,:/home/sysadmin:/bin/bash

Make the same change in the "group" file;

vi /etc/group

Change the "sysadmin" line to;

sysadmin:x:999:

Changing the uid of a user will break the permissions in their home directory;
~# ls -al /home/sysadmin
total 32
drwxr-xr-x 3 1000 1000 4096 2012-05-13 13:34 .
drwxr-xr-x 3 1000 1000 4096 2012-05-13 13:32 ..
-rw------- 1 1000 1000 48 2012-05-13 13:34 .bash_history
-rw-r--r-- 1 1000 1000 220 2012-05-13 13:32 .bash_logout
-rw-r--r-- 1 1000 1000 3103 2012-05-13 13:32 .bashrc
drwx------ 2 1000 1000 4096 2012-05-13 13:33 .cache
-rw-r--r-- 1 1000 1000 675 2012-05-13 13:32 .profile
-rw-r--r-- 1 1000 1000 0 2012-05-13 13:33 .sudo_as_admin_successful
-rw------- 1 1000 1000 663 2012-05-13 13:34 .viminfo

You can fix that by issuing the following commands;

~# chown sysadmin:sysadmin /home/sysadmin
~# chown sysadmin:sysadmin /home/sysadmin/.*

When we setup LDAP later we will want to mount /home to an NFS share. Unfortunately, when we do this we will overwrite our sysadmin's home folder! Let's move it to the root ("/") directory.

~# mv /home/sysadmin /

We will need to change the path in the passwd file;

~# vi /etc/passwd

Change it from;

sysadmin:x:999:999:sysadmin,,,:/home/sysadmin:/bin/bash

to this;

sysadmin:x:999:999:sysadmin,,,:/sysadmin:/bin/bash

Check that all is well;
~# ls -al /sysadmin
total 32
drwxr-xr-x 3 sysadmin sysadmin 4096 2012-05-13 13:34 .
drwxr-xr-x 23 root root 4096 2012-05-14 11:29 ..
-rw------- 1 sysadmin sysadmin 48 2012-05-13 13:34 .bash_history
-rw-r--r-- 1 sysadmin sysadmin 220 2012-05-13 13:32 .bash_logout
-rw-r--r-- 1 sysadmin sysadmin 3103 2012-05-13 13:32 .bashrc
drwx------ 2 sysadmin sysadmin 4096 2012-05-13 13:33 .cache
-rw-r--r-- 1 sysadmin sysadmin 675 2012-05-13 13:32 .profile
-rw-r--r-- 1 sysadmin sysadmin 0 2012-05-13 13:33 .sudo_as_admin_successful
-rw------- 1 sysadmin sysadmin 663 2012-05-13 13:34 .viminfo

On another console, confirm that you can login as the sysadmin user.

You should get a proper bash prompt;

sysadmin@ldapds:~$

Note:
If your system has a GUI login, be aware that the logon screen will not display usernames for users with a UID of less than 1000. To login using the "sysadmin" account in such a case, you would need to type the name in to the username field manually.

Create WMQ QueueManager using script

Here is a handy script to make QM on Centos. This should be run after switching to mqm user.

Save the following as create_qm.sh

#!/bin/bash 
#############################################

##            Main Routine 
#############################################

main(){
echo "Checking if [$qm] exists?..."
qm=`dspmq | awk '{ print $1 }' | sed 's/QMNAME(//g;s/)//g' | grep -o $qm`
if [ "$qm" = "" ];
then
echo "Creating: [$qm]"
`crtmqm $qm`
echo "Successfully created $q, Exiting with value 0"
 else 
echo "[$qmname], already exists"
status=`dspmq -m $qmname| cut -d '(' -f2,3 | cut -d ')' -f2 | cut -d '(' -f2`
echo status of queue manager [$qm] is [$status]
fi
echo "Exiting Main Routine.. "
}
#############################################

##                 Entry Point 
#############################################

if [ ! "$1" ];
then
echo "Fail: You must pass in a queue manager name"
exit 1
else
qm=$1
echo "Queue Manager to create = $qm"
echo "Calling Main function ... "
main $*
exit 0 
fi

Use following command to create Queue Manager

create_qm.sh TEST_QM1

Install WMQ6.0 on Centos

This article explains step-by-step installation of WMQ6.0 on Centos 6.0.

Download WMQ6.0 from IBM Website ( login required)
After downloading the package and extracting the same on /tmp, accept license by running mqlicense.sh script
Install the packages, commands listed below

rpm -ivh MQSeriesServer-6.0.2-3.i386.rpm

rpm -ivh MQSeriesRuntime-6.0.2-3.i386.rpm

rpm -ivh MQSeriesSDK-6.0.2-3.i386.rpm

rpm -ivh MQSeriesSamples-6.0.2-3.i386.rpm

rpm -ivh MQSeriesClient-6.0.2-3.i386.rpm

rpm -ivh MQSeriesJava-6.0.2-3.i386.rpm

rpm -ivh MQSeriesTXClient-6.0.2-3.i386.rpm

rpm -ivh MQSeriesServer-6.0.2-3.i386.rpm

rpm -ivh MQSeriesMan-6.0.2-3.i386.rpm

rpm -ivh --nodeps MQSeriesFTA-6.0.2-3.i386.rpm

rpm -ivh --nodeps MQSeriesIES30-6.0.2-3.i386.rpm

rpm -ivh --nodeps MQSeriesConfig-6.0.2-3.i386.rpm

rpm -ivh MQSeriesKeyMan-6.0.2-3.i386.rpm

rpm -ivh gsk7bas-7.0-4.11.i386.rpm

rpm -ivh IBMJava2-142-ia32-SDK-1.4.2-9.0.i386.rpm

Done.

A Brief outline on IBM Webshpere MQ (WMQ)

IBM Websphere MQ (WMQ or MQ Series) is a middleware for messaging in a cross platform environment. MQI - Message Queue Interface - api used to commmunicate with a Message Queue Manager (MQM).

Queue Manager (MQM)

Manages queues and messages for applications
Transfers messages to other Queue Managers via channels using existing network facilities.
It refers to objects that are defined by the administrator.
Coordinates updates to databases and queues using two-phase commit.
Gets and puts from/to queues are committed together with SQL updates, or backed out if necessary.
Segments messages, if necessary, and assembles them.
Can group messages and send them as one physical message to their destination, where they are automatically disassembled.
Can send one message to more than one destination using a user-defined dynamic destination list.
Allow administrators to create and delete queues, alter properties of existing queues,control the operation of queue manager.
Front-end available on Eclipse to manage Queue Manager

Queue Manager Clusters

Queue Managers that form a cluster can run in the same machine or in different machines on different platforms.
Two of Queue Managers maintain a repository that contains information about all queue managers and queues in the cluster (full repository). Other Queue Managers maintain only a repository of the objects they are interested in (partial repository).
Queue Managers use special cluster channels to exchange information.
Client application may specify a queue manager and direct the message to a specific queue in a cluster or it may let a queue manager to determine where the queue is and to which one to send the message.
Client uses a Transmission Queue on its machine and destination queue is called “Target Queue”.
Administrator must define the name of the cluster, when a queue is defined.
MQSeries distributes the messages round robin.

Queue Manager Objects

A Queue Manager uses 3 types of objects, namely, Queues, Process Definitions and Channels.
Queues are used to store messages.
Process Definition object defines an application to a queue manager. It contains a name of a program (and its path) to be triggered when a message arrives for it.
Channel is a communication link. There are 2 kinds of channels, namely, Message Channels and MQI channels.
Message Channel connects 2 queue managers via Message Channel Agents (MCA). Message Channel is unidirectional.
MCA is a program (also called mover) that transfers messages from a transmission queue to a communication link and from communication link to a target queue.
MQI channel connects MQSeries client to a queue manager and is bi-directional.
Message Channel can run at 2 speeds: fast and normal. Fast Channels improve performance but messages can be lost in case of channel failure.

Message Queues

Message Queues belong to Queue Manager.
Types of Messages Queues are:

Local Queue – is a real queue
Cluster Queue – is a local queue that is known throughout a cluster of queue managers.
Remote Queue – structure describing a queue hosted by a different queue manager.
Transmission Queue – a local queue used for messages to be sent to a remote queue.
Initiation Queue – local queue with a special purpose
Dynamic Queue – local queue created on the fly
Alias Queue - if you do not like the queue name
Dead-Letter Queue – one for each queue manager
Reply-to Queue – specified in request message
Model Queue – model for local queues
Repository Queue – hold cluster information

Saturday, May 19, 2012

HOWTO: Change your default user account to a system account

Create WMQ QueueManager using script

Install WMQ6.0 on Centos

A Brief outline on IBM Webshpere MQ (WMQ)