postgresql Cluster

List All Cluster:

    root@debian:~# pg_lsclusters
    Ver Cluster Port Status Owner    Data directory               Log file
    9.6 main    5432 online postgres /var/lib/postgresql/9.6/main     /var/log/postgresql/postgresql-9.6-main.log

Find Status of given instance:

    root@debian:~# pg_ctlcluster 9.6 main  status
    pg_ctl: server is running (PID: 6062)
    /usr/lib/postgresql/9.6/bin/postgres "-D" "/var/lib/postgresql/9.6/main" "-c" "config_file=/etc/postgresql/9.6/main/postgresql.conf"

Kill Process:

    sudo kill -SIGHUP  6062

Change Status of instance – start/stop:

    pg_ctlcluster 9.6 main  stop
    pg_ctlcluster 9.6 main  start
    pg_ctlcluster 9.6 main  restart

View Cluster Configuration:

    root@debian:~# pg_ctlcluster 9.6 main  status
    pg_ctl: server is running (PID: 6062)
    /usr/lib/postgresql/9.6/bin/postgres "-D" "/var/lib/postgresql/9.6/main"     "-c" "config_file=/etc/postgresql/9.6/main/postgresql.conf"
    root@debian:~# ^C
    root@debian:~# pg_conftool 9.6 main show all
    cluster_name = '9.6/main'
    data_directory = '/var/lib/postgresql/9.6/main'
    datestyle = 'iso, mdy'
    default_text_search_config = pg_catalog.english
    dynamic_shared_memory_type = posix
    external_pid_file = '/var/run/postgresql/9.6-main.pid'
    hba_file = '/etc/postgresql/9.6/main/pg_hba.conf'
    ident_file = '/etc/postgresql/9.6/main/pg_ident.conf'
    lc_messages = en_IN
    lc_monetary = en_IN
    lc_numeric = en_IN
    lc_time = en_IN
    log_line_prefix = '%t [%p-%l] %q%u@%d '
    log_timezone = localtime
    max_connections = 100
    port = 5432
    shared_buffers = 128MB
    ssl = true
    ssl_cert_file = '/etc/ssl/certs/ssl-cert-snakeoil.pem'
    ssl_key_file = '/etc/ssl/private/ssl-cert-snakeoil.key'
    stats_temp_directory = '/var/run/postgresql/9.6-main.pg_stat_tmp'
    timezone = localtime
    unix_socket_directories = '/var/run/postgresql'

Create New Cluster:
     pg_createcluster 9.6 new_cluster

DROP Cluster:
     pg_dropcluster --stop 9.6 main

Update Cluster:
     pg_upgradecluster 9.5 main

    it upgrades to next version

Reload Configuration:
      pg_ctlcluster 9.6 main reload

Restart Postgres Service:
    root@debian:~# systemctl reload postgresql

CHECK if Postgres is Listensing :

    root@debian:~# pg_isready
    /var/run/postgresql:5432 - accepting connections