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PG operation and maintenance -- service start and stop

2022-07-16 08:50:00 【51CTO】

pg Start stop

Kai Ku

（1） Direct operation postgres The process starts

postgres -D /home/osdba/pgdata &

-D Used to specify the data directory , Command the last & Indicates background execution

（2） Use pg_ctl Command to start

pg_ctl -D /home/osdba/pgdata start

Stop storage

（1） Direct to running postgres The main process sends signal The signal , Stop database

（2） Use pg_ctl Command to stop the database

Three modes to stop a database

（1）smart shutdown

New connections are not allowed , Wait until all existing connections are completed before closing the database .

（2）fast shutdown

Quick off mode , New connections are no longer allowed , Send to all active service processes SIGTERM The signal , Let them exit immediately , Wait for all child processes to exit and shut down the database . If the service is in online backup state , The backup will be terminated directly .

（3）immediate shutdown

Turn off mode immediately , The main process postgres Send... To all child processes SIGQUIT The signal , And quit immediately , All child processes will also exit immediately . When exiting in this mode , It will not shut down the database system properly , The database will replay the next time you start wal Log recovery .

The operation is as follows

       
       pg_ctl 
       
       -D 
       
       /opt
       
       /pgdata stop 
       
       -ms   Equivalent to   Wait for the connection to close 
       
pg_ctl 
       
       -D 
       
       /opt
       
       /pgdata stop 
       
       -mf   Equivalent to   Kill the conversation , Roll back , close 
       
pg_ctl 
       
       -D 
       
       /opt
       
       /pgdata stop 
       
       -mi   Equivalent to   kill 
       
       -
       
       9
      
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pg_ctl Tools

function

（1） Initialize database instance

       
       pg_ctl init
       
       [db
       
       ]  
       
       [
       
       -s
       
       ] 
       
       [
       
       -D datadir 
       
       ] 
       
       [ 
       
       -o options
       
       ]
       
       -s Print error and alarm information 
       
       -D datadir  Specify the data directory of the database instance 
      
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（2） start-up 、 End 、 restart pg

       
       pg_ctl 
       
       -D 
       
       /opt
       
       /pgdata 
       
       -l logfile start  start-up 
       
pg_ctl 
       
       -D 
       
       /opt
       
       /pgdata restart 
       
       &         restart 
      
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（3） see pg state

       
       pg_ctl status 
       
       -D 
       
       /opt
       
       /pgdata 
      
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（4） Let the database instance read the configuration file again

       
       pg_ctl 
       
       -D 
       
       /opt
       
       /pgdata reload            Reread the configuration file 
      
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（5） Allows a signal to be sent to a specified process

       
       SIGTERM：smart shutdown  Shutdown mode 
       
SIGINT： fast shutdown  Shutdown mode 
       
SIGQUIT： immediate shutdown  Shutdown mode 
      
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Use pg_ctl reload Commands and direct call functions pg_reload_conf() The essence is to send SIGHUP Command to the service main process .

Single user mode

Refers to start pg When combined with --single Parameters , At this time pg The process will not enter the background service mode , For the following scenarios

（1）initdb Stage

（2） Repair the system table

（3） When multi-user mode does not accept all commands , You can use single user mode to connect to the database

PG The transaction age of one record in cannot exceed 2^{31, If beyond this range , This data will be lost ,pg This is not allowed , When recording the age distance 2}31 There are still 10 million times , There will be an alarm in the log . If you don't deal with , There are still onemillion hours , The database server will automatically disable connections from any user .

In this case , You can only start the database in single user mode VACUUM Name to repair .

       
       postgres 
       
       --single -D /opt/pgdata
       
...
       
VACUUM FULL
       
       ;
       
...
       
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