install

yum install postgresql-server
systemctl list-unit-files  -t service
systemctl is-enabled postgresql.service

start daemon

systemctl status postgresql.service
postgresql-setup initdb
systemctl start postgresql.service
su - postgres
psql -l

sql command operation

psql << END
\du
\q
END
psql -c "select * from pg_user"

create and drop user

\du
SELECT * FROM pg_user;
createuser -P ossdb
dropuser -i ossdb
CREATE USER ossdb LOGIN PASSWORD 'password';
DROP USER IF EXISTS ossdb;

create and drop database

\l
SELECT * FROM pg_database;
createdb -O ossdb -W ossdb
dropdb -i ossdb
CREATE DATABASE ossdb OWNER ossdb;
DROP DATABASE IF EXISTS ossdb;

connect

cat << END >> /var/lib/pgsql/data/pg_hba.conf
host    ossdb           ossdb           127.0.0.1/32            md5
END
systemctl reload postgresql.service
psql -U ossdb -d ossdb -h 127.0.0.1

create and drop table

\dit
\d table_name
CREATE TABLE t1 (
c1 integer,
c2 date,
c3 time,
c4 character,
c5 character varying(16),
c6 real,
primary key (c1), 
unique (c2, c3)
);
DROP TABLE IF EXISTS  t1;

パッケージ更新

uname -a
yum check-update
yum update

chronyの設定

yum list chrony
ls -l /etc/chrony.conf*
cp -pi /etc/chrony.conf /etc/chrony.conf.000
ls -l /etc/chrony.conf*
diff -u /etc/chrony.conf{,.000}

systemctl status chronyd.service
ps -ef | grep chronyd | grep -v grep
chronyc sources
chronyc tracking
chronyc sourcestats
chronyc -a makestep

systemctl restart chronyd.service

サービスの自動起動設定と解除

systemctl list-unit-files  -t service
systemctl is-enabled chronyd.service

systemctl disable chronyd.service
systemctl enable chronyd.service

パッケージ削除と確認

yum remove chrony
yum list chrony

パッケージ導入

yum install ntp
yum list ntp

サービス起動

systemctl status ntpd.service
systemctl start ntpd.service