Postgresql database installation and common error reporting problems

/var/lib/pgsql: used to store the default data folder of the Postgres database
/usr/pgsql-9.6: used to store commands for the Postgres database, relying on information such as libraries and document directories
/var/lib/pgsql/9.6/data: The user stores the pg_hba.conf and postgresql.conf configuration files of PG default configuration

In order to simplify the later operation and maintenance, add postgresql to the system PATH, and test whether the postgres command returns, and test whether the installation is successful

Create a folder:

mkdir -p /var/lib/pgsql/{data,xlog_archive}

chown -R postgres:postgres /var/lib/pgsql/

chmod 0700 /var/lib/pgsql/data

Edit environment variables

vi /etc/profile

# Add the following statement at the end of the file

export PGDATA=/var/lib/pgsql/data

export PATH=$PATH:/usr/pgsql-9.6/bin

make the environment variable take effect

source /etc/profile

postgres --version

Initialize the database

After the data is configured (if a custom path is configured), the database is not started by default. Initialization is required.

Method 1: sudo -u postgres /usr/pgsql-9.6/bin/initdb -D /data/postgres/ under the root user

Method 2: su - postgres

initdb -D /var/lib/pgsql/data

If you want to connect other servers to pg, you need to change the parameter settings:

Modify postgresql.conf

vi /var/lib/pgsql/data/postgresql.conf

listen_addresses = '*'

Modify pg_hba.conf

vi /var/lib/pgsql/data/pg_hba.conf

Added: host all all 0.0.0.0/0 md5

Start the postgres database

are postgres

pg_ctl -D /var/lib/pgsql/data/start

The corresponding command to stop the pg database is:

pg_ctl -D /var/lib/pgsql/data/ stop

login pg

psql -h localhost -U postgres -d postgres -W

Detailed psql command :

-h host, specify the IP address of the Postgres database to connect to
-U username: Specify the username to connect to the database
-d database: Specify the database name to connect to
-p port: specify the service port of the database connection
-w: Indicates that the user is not prompted for a password
-W : Indicates to verify the database user password
-l : Indicates to list the database information available to Postgres

Postgresql uninstallation

yum remove postgresql*

and then check to see if there are

rpm -qa|grep postgres

Commonly used Postgresql commands:

View all databases: =# \l or \list
List the tables of the current database: =# \d
Create a database: =# create database mydb;
Switch databases: =# \c mydb
Insert a table in the current database: =# create table test (id int, body varchar(100));
Create a new user: =# create user test with password 'test';
Modify the account password: =# alter user postgres with encrypted password 'mypass';
Grant the specified account to the specified database permission: = # grant all privileges on database mydb to test;
Remove the specified account to the specified database permission: =# revoke all privileges on database mydb to test;

One-click restart postgresql script

Restarting postgresql sometimes results in the following error 3: could not create lock file "/var/run/postgresql/.s.PGSQL.5432.lock": No such file or directory, you can use this script command to restart pg with one click:

The script checks to restart if pg is running, and starts if pg is not running

sh start_postgresql.sh /data/XXX (your startup address)

Script command to restart postgresql with one key in Linux-PostgreSQL Documentation Resources-CSDN Download

common error

Error 1: Installing the rpm package lacks dependencies

Error error: Failed dependencies:

libxslt.so.1()(64bit) is needed by postgresql96-contrib-9.6.20-1PGDG.rhel6.x86_64

libxslt.so.1(LIBXML2_1.0.11)(64bit) is needed by postgresql96-contrib-9.6.20-1PGDG.rhel6.x86_64

libxslt.so.1(LIBXML2_1.0.18)(64bit) is needed by postgresql96-contrib-9.6.20-1PGDG.rhel6.x86_64

libxslt.so.1(LIBXML2_1.0.22)(64bit) is needed by postgresql96-contrib-9.6.20-1PGDG.rhel6.x86_64

solution:

Just install dependencies: yum install libxslt

Error 2: su postgres shows the problem of bash-4.2$

Delete the postgres user and recreate the user

userdel postgres

useradd postgres

Notice:

Remember to re-assign permissions after deleting and rebuilding the user

chown -R postgres:postgres /var/lib/pgsql/

Error 3: s.PGSQL.5432.lock" does not exist

FATAL: could not create lock file "/var/run/postgresql/.s.PGSQL.5432.lock": No such file or directory

< 2021-02-06 08:27:44.357 EST > LOG: database system is shut down

Solution: just create a folder

mkdir -p /var/run/postgresql/

chown -R postgres:postgres /var/run/postgresql/

Error 4: The error link cannot be accessed because the firewall is not closed! ! !

systemctl status firewalld

报错5：Postgresql FATAL: could not create semaphores: No space left on device

Reference article link:

Postgresql FATAL: could not create semaphores: No space left on device_dazuiba008's Blog-CSDN Blog

For my own situation, modifying the above parameters is invalid. After killing all vnc processes, restarting pg is successful.

Detailed explanation of PostgreSQL's pg_hba.conf configuration parameters

Detailed explanation of PostgreSQL's pg_hba.conf configuration parameters - Programmer Sought

What to do if you forget your password, you can change the pg_hba.conf file:

Modify the pg_hba.conf file under the data directory
local all all md5=>change to trust
save and exit, then use pg_ctl reload to re-read the pg_hba.conf file to make the configuration take effect
Enter the postgresql database
alter user postgres with password 'the password you want to set ';
Then change the trust modified in pg_hba.conf back to the original md5