Процессы операционной системы

postgres$ ps -o pid,command --ppid `head -n 1 $PGDATA/postmaster.pid`
  PID COMMAND
 1822 postgres: 9.6/main: checkpointer process   
 1823 postgres: 9.6/main: writer process   
 1824 postgres: 9.6/main: wal writer process   
 1825 postgres: 9.6/main: autovacuum launcher process   
 1826 postgres: 9.6/main: stats collector process   
15147 postgres: 9.6/main: autovacuum worker process   plpgsql_exceptions

К процессам, обслуживающим буферный кэш и журнал, можно отнести:

Остановка в режиме fast

postgres$ rm $LOG
pg_ctlcluster 9.6 main restart

Журнал сообщений сервера:

postgres$ cat $LOG
2017-07-22 23:41:17 MSK [18010-1] LOG:  database system was shut down at 2017-07-22 23:41:16 MSK
2017-07-22 23:41:17 MSK [18010-2] LOG:  MultiXact member wraparound protections are now enabled
2017-07-22 23:41:17 MSK [18009-1] LOG:  database system is ready to accept connections
2017-07-22 23:41:17 MSK [18014-1] LOG:  autovacuum launcher started
2017-07-22 23:41:18 MSK [18016-1] [unknown]@[unknown] LOG:  incomplete startup packet

Остановка в режиме immediate

postgres$ rm $LOG
pg_ctlcluster 9.6 main stop
pg_ctlcluster 9.6 main restart

Журнал сообщений сервера:

postgres$ cat $LOG
2017-07-22 23:41:20 MSK [18083-1] LOG:  database system was interrupted; last known up at 2017-07-22 23:41:17 MSK
2017-07-22 23:41:20 MSK [18084-1] [unknown]@[unknown] LOG:  incomplete startup packet
2017-07-22 23:41:21 MSK [18083-2] LOG:  database system was not properly shut down; automatic recovery in progress
2017-07-22 23:41:21 MSK [18083-3] LOG:  invalid record length at D/6BF54D20: wanted 24, got 0
2017-07-22 23:41:21 MSK [18083-4] LOG:  redo is not required
2017-07-22 23:41:21 MSK [18083-5] LOG:  MultiXact member wraparound protections are now enabled
2017-07-22 23:41:21 MSK [18082-1] LOG:  database system is ready to accept connections
2017-07-22 23:41:21 MSK [18090-1] LOG:  autovacuum launcher started

Перед тем, как начать принимать соединения, СУБД выполнила восстановление (automatic recovery in progress).