[Postgres] Postgres database migration

Environmental statement

This content completes the test based on the following environment

term	Configuration instructions	remarks
operating system	CentOS7
PG Data version	9.6.24
Operating system users	root/postgres
Data volume	user （20）、 role （20）、 database （2）、schema（42）、 Data volume （ about 160W That's ok ）	Data file approx 640M

Backup

The data backup

# Create a backup storage folder （ Make sure postgres The user has permission ）
cd /home
mkdir posrgres
chown -R postgres postgres/
# Switch postgres user 
su - posrgres
# Perform backup 
pg_dumpall -U postgres -v -f u_postgres.backup

File backup

Default location of data file ：/var/lib/pgsql/9.6

# Switch to the data storage location 
cd /var/lib/pgsql/9.6
# Stop database service 
systemctl stop postgresql-9.6
# Compressed data file 
tar -cvf data.tar.gz data/
# Got  data.tar.gz  This is the compressed data backup file 

Migration scheme 1 ： Data file migration

Migrate data files

This process needs to be stopped first pg database

Complete the file backup

# Ensure that process services are stopped 
systemctl stop postgresql-9.6
cd /home
# Create a migration Directory   And modify the authority 
mkdir pgdata
## Modify attribution 
chown -R postgres pgdata/
## Modify the permissions （ must ）
chmod 700 pgdata/
# Switch to pg user 
 su - postgres
# Copy data file to new location 
cp -rf data/* /home/pgdata/

Modify the location of the service data file

# Edit service profile 
vim  /usr/lib/systemd/system/postgresql-9.6.service
# Modify the data file path of the configuration file 
 modify ：Environment=PGDATA=/var/lib/pgsql/9.6/data/
 by ：Environment=PGDATA=/home/pgdata/
# Save and exit 
# Restart the system 
reboot

Migration scheme II ： Data reduction method

This scheme is based on pg Database support for backup and restore , Using this method, it is strongly recommended to operate on the same version of the database

For data backup, see **【 The data backup 】** chapter

Upload data backup file

# Create a backup file location 
cd /home
mkdir postgres
# Upload the backup file to the storage location in the previous step （ Upload process omitted ）
mv u_postgres.backup postgres/
# Modify the permissions 
chown -R postgres postgres/

Use psql Restore

# Switching users 
su - postgres
# Switch data backup directory 
cd /home/postgres/
# Perform recovery （ Ignore mistakes ,"postgres" Built in role reason ）
psql -U postgres  -f u_postgres.backup
# Perform recovery （ Stop on error , Don't suggest ）
#psql -U postgres --set ON_ERROR_STOP=on -f u_postgres.backup

Common problems and Solutions

The permission is too large

• The permission of the migration target directory is too large

terms of settlement ： Modify the permissions （ must ）
chmod 700 pgdata/

Directory error or insufficient permissions

• The directory caused by incorrect operation cannot be recognized as a valid path or is caused by incorrect permission modification

terms of settlement ： Modify the folder where the data file is located to posrgres all

chown -R postgres pgdata

chown 700 pgdata

# The swappable postgres Test read and write permissions