Процессы операционной системы 

postgres$ ps -o pid,command --ppid `head -n 1 $PGDATA/postmaster.pid`

  PID COMMAND
 9241 postgres: checkpointer process   
 9242 postgres: writer process   
 9243 postgres: wal writer process   
 9244 postgres: autovacuum launcher process   
 9245 postgres: stats collector process   
 9246 postgres: bgworker: logical replication launcher

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

Остановка в режиме fast 

postgres$ rm /home/postgres/logfile

postgres$ pg_ctl -w -l /home/postgres/logfile -D /usr/local/pgsql/data restart

waiting for server to shut down.... done
server stopped
waiting for server to start.... done
server started

Журнал сообщений сервера: 

postgres$ cat /home/postgres/logfile

2019-03-31 15:24:09.505 MSK [9775] LOG:  listening on IPv4 address "0.0.0.0", port 5432
2019-03-31 15:24:09.505 MSK [9775] LOG:  listening on IPv6 address "::", port 5432
2019-03-31 15:24:09.507 MSK [9775] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"
2019-03-31 15:24:09.526 MSK [9776] LOG:  database system was shut down at 2019-03-31 15:24:09 MSK
2019-03-31 15:24:09.529 MSK [9775] LOG:  database system is ready to accept connections

Остановка в режиме immediate 

postgres$ rm /home/postgres/logfile

postgres$ pg_ctl -w -D /usr/local/pgsql/data stop -m immediate

waiting for server to shut down.... done
server stopped

postgres$ pg_ctl -w -l /home/postgres/logfile -D /usr/local/pgsql/data start

waiting for server to start.... done
server started

Журнал сообщений сервера: 

postgres$ cat /home/postgres/logfile

2019-03-31 15:24:09.843 MSK [9834] LOG:  listening on IPv4 address "0.0.0.0", port 5432
2019-03-31 15:24:09.843 MSK [9834] LOG:  listening on IPv6 address "::", port 5432
2019-03-31 15:24:09.846 MSK [9834] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"
2019-03-31 15:24:09.865 MSK [9835] LOG:  database system was interrupted; last known up at 2019-03-31 15:24:09 MSK
2019-03-31 15:24:10.118 MSK [9835] LOG:  database system was not properly shut down; automatic recovery in progress
2019-03-31 15:24:10.120 MSK [9835] LOG:  invalid record length at 0/17AD8BC: wanted 24, got 0
2019-03-31 15:24:10.120 MSK [9835] LOG:  redo is not required
2019-03-31 15:24:10.129 MSK [9834] LOG:  database system is ready to accept connections

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