PostgreSQL: Unable to run repmgr cloned database
I searched around and realized that the problem was due to not enabling hot_standby on the standby server. I wrote a corrected, updated and simplified version of the above article as an odt for future personal reference. Here is the text in its entirety (converted to html from odt using openoffice.org) for those who are interested in setting up a single read-only clone of a database using repmgr:



Single Slave Streaming Replication with
PostgreSQL

Introduction
This guide aims to quickly help you configure a PostgreSQL 9.1
server with a database, and have it replicated to a slave that can be
used for read-only queries. There is no concept of failover involved
here, and the slave will only have a read-only copy of the master's
data.

1. Tools Needed

    A stable GNU/Linux Distribution (Recommended OS: CentOS 6.2 x86-64)
    PostgreSQL 9.1 – you may install from here: http://yum.postgresql.org/ (also make sure that the following packages or their equivalnets are installed)
    
        postgresql
        postgresql-client
        postgresql-contrib
        postgresql-server
        postgresql-server-dev
    2 workstations – a master that runs the primary database
    and a slave that runs the replicated read-only database (for the
    purpose of this document, their respective IP addresses have been
    replaced with pgmaster and pgslave so
    make those changes in /etc/hosts of both machines if you want to
    follow the following instructions word for word)


2. Installation Check and Password Creation

    Run /etc/init.d/postgresql start on both systems to check if PostgreSQL is functional or not.
    Run /etc/init.d/postgresql stop on both systems to stop PostgreSQL. We will not be using PostgreSQL till we finish some configuration related tasks.
    Set a password for user postgres on both the systems. This user by default has no password, but we need a password to help create an SSH tunnel between pgmaster and pgslave.
    Run sudo passwd postgres on both systems and type a new Unix password for both.


3. SSH Tunnel Creation

    On the pgmaster do the following:
    su postgres
    ssh-keygen -t rsa (press enter at every prompt)
    ssh-copy-id -i ~/ssh/id_rsa.pub pgslave  (you need to enter pgslave's postgres password)
    ssh pgslave and see if you are able to login without password
    Repeat the above steps on pgslave
    su postgres
    sh-keygen -t rsa
    ssh-copy-id -i ~/ssh/id_rsa.pubaster
    ssh pgmaster and see if you are able to login without password
    Make sure you log out from the remote machine after you finish checking connectivity


4. Editing postgresql.conf on pgmaster
You need to make the following changes in the file
postgresql.conf that resides in the configuration
directory inside /etc/postgresql/
on your machine pgmaster:

    listen_addresses = '*'
    wal_level = hot_standby
    checkpoint_segments=30
    archive_mode=on
    archive_command='cd .'
    max_wal_senders=2
    wal_keep_segments=5000


5. Editing postgresql.conf on pgslave
You need to make the following change in the file postgresql.conf
that resides in the configuration directory inside /etc/postgresql/
on machine pgslave:

    hot_standby=on


6. Editing pg_hba.conf on pgmastger
You need to make the following changes in the file pg_hba.conf
that resides in the configuration directory inside /etc/postgresql/
on machine pgmaster:

    host all all 192.168.5.0/24 trust
    host replication all 192.168.5.0/24   trust


7. Adding PostgreSQL bin folder to PATH
There are a bunch of nifty postgresql utilities we will be using
here, so lets set the PATH variable so that it knows where to find
them

    Execute locate pgbench
    The output will be something like /usr/lib/postgresql/9.1/bin/pgbench
    Excluding final word pgbench, copy the above path and add it to your path variable.
    Execute nano ~/.bashrc
    add line export PATH+=:/usr/lib/postgresql/9.1/bin/ (or whatever location the locate command revealed)
    Close the file and save changes
    You may need to log out and login (or open a new shell) for changes to take effect.


8. Loading pgmaster's PostgreSQL server with
dummy data

    On pgmaster start the PostgreSQL server first: /etc/init.d/postgresql start
    We create a test database and load it with some dummy data with the following commands:
    
        su postgres
        createdb pgbench
        pgbench -i -s 10 pgbench
    
    Alternatively open the database pgbench yourself, create a sample table and insert sample data into it.


9. Erasing pgslave's data and checking pgmaster
connectivity

    We are going to erase data directory of pgslave, so execute following on that machine:
    First stop PostgreSQL server /etc/init.d/postgresql stop
    Move into the PostgreSQL default data directory folder: cd /var/lib/pgsql/data (or to the data directory that is default for your installation)
    Empty the directory completely with rm -rf *
    Now execute psql -h pgmaster -d pgbench and see if you are able to access the database on pgmaster through pgslave.


10. Installing repmgr
Though single slave replication is fairly straightforward, we are
using a tool called repmgr to help make the process even more simpler. Here is how you install it:

    Grab repmgr source code from http://projects.2ndquadrant.it/sites/default/files/repmgr-1.1.0.tar.gz
    and copy it to /tmp for installation.
    Have the following packages installed to ensure that compiling repmgr is possible:
    
        make
        gcc
        postgresql-devel
        libxslt-devel
        pam-devel
        libopenssl-devel
        krb5-devel
    
    Extract the downloaded archive and enter the source code folder.
    Compile with make USE_PGXS=1
    Install with make USE_PGXS=1 install
    Execute below two commands to check if repmgr is installed correctly:
    
        repmgr --version
        repmgrd --version
    


11. Cloning pgmaster onto pgslave using repmgr

    Execute su postgres and login as the postgres user on pgslave
    Run this to clone database: repmgr -D /var/lib/pgsql/data -d pgbench -p 5432 -R postgres --verbose standby clone pgmaster
    Note that the -D parameter /var/lib/pgsql/data should be replaced with the appropriate location of the data folder on pgslave
    Also note that 5432 is the default port PostgreSQL runs in.
    When the command finishes executing (it is going to take several seconds to finish if you had used pgbench to insert random data) you may start PostgreSQL on pgslave with /etc/init.d/postgresql start


12. Testing streaming replication
Congratulations! You have successfully configured pgslave
to copy pgmaster's database via
streaming replication. Note that due to being in continuous recovery
mode, pgslave can only be used to
execute read-only queries and no
insertions or modifications are possible.

    Insert some values into sample_table on pgmaster.
    execute select * from sample_table; on pgslave's psql prompt after connecting to pgbench database.
    If everything worked properly, you should be able to view newly added tupples on the output from pgslave.


Conclusion
We just learned how to quickly configure a PostgreSQL database to
act as a read-only mirror to another database. Note that in case the
slave goes offline, it will automatically recover data from the
master and would be soon up-to-date. Streaming replication is at
database level, so you need to execute the command in part 11for each
new database that needs to be replicated via streaming replication.