doc(pg) add postgres backup doc (#534)

add postgres backup doc

Signed-off-by: zhuhuijun <zhuhuijunzhj@gmail.com>

A doc PR, directly merge now.

docs/LCM/backup-psql-data.md

@@ -2,4 +2,102 @@
 
 Documentation shown here guides you how to backup the psql database data.
 
-TBD
+## get postgresql username and password from secret
+
+- First, we use kubectl search secret which stores the harbor database username and password.
+
+```shell
+
+kubectl get secret -n cluster-sample-ns|grep credentials|grep ^harbor
+harbor.postgresql-cluster-sample-ns-ghostbaby-rs.credentials     Opaque                                2      11s
+
+```
+
+- Second, we get the username and password.
+
+```shell
+
+kubectl get secret harbor.postgresql-cluster-sample-ns-ghostbaby-rs.credentials -n cluster-sample-ns -o jsonpath="{.data.username}" | base64 --decode
+harbor
+
+kubectl get secret harbor.postgresql-cluster-sample-ns-ghostbaby-rs.credentials -n cluster-sample-ns -o jsonpath="{.data.password}" | base64 --decode
+UT6Jo1L8QUhgzB2cqD70xWjwY97fNDxw5vWSULznV0IIinTlEaE9OBypn3UH2uYO
+
+```
+
+## backup postgres harbor database
+
+- find postgres pod
+
+```shell
+
+kubectl get pod -n cluster-sample-ns |grep postgresql
+postgresql-cluster-sample-ns-ghostbaby-rs-0                1/1     Running   0          9m19s
+
+```
+
+- login postgres pod
+
+```shell
+
+kubectl exec -it postgresql-cluster-sample-ns-ghostbaby-rs-0 -n cluster-sample-ns -- /bin/bash
+
+```
+
+- save postgres backup shell script
+
+```shell
+
+#!/bin/bash
+set -ex
+# define postgresql connect url
+export PGHOST='127.0.0.1'
+export PGPORT='5432'
+export PGUSER='harbor'
+export PGPASSWORD='UT6Jo1L8QUhgzB2cqD70xWjwY97fNDxw5vWSULznV0IIinTlEaE9OBypn3UH2uYO'
+# define backup dir
+BASE_DIR='/data/pgsql-dump'
+# define backup filename
+FILENAME='pgsql-dump'
+# define data format，20190329-00
+DATE=$(date +%Y%m%d)
+TIME=$(date +%H%M)
+# render backup full path
+BACKUP_DIR="${BASE_DIR}/${DATE}/${TIME}"
+mkdir -p ${BACKUP_DIR}
+# get backup database list
+DATABASES=$(psql --host=${PGHOST} --port=${PGPORT} --username=${PGUSER} -c "\l" | awk '{print$1}' | xargs)
+# exec pg_dump to backup data
+for DB in $DATABASES;do
+    pg_dump --host=${PGHOST} --port=${PGPORT} --username=${PGUSER} --verbose --clean --create ${DB} | gzip -c > ${BACKUP_DIR}/${FILENAME}_${DB}.gz
+done
+# backup all databases
+pg_dumpall --host=${PGHOST} --port=${PGPORT} --username=${PGUSER} --verbose --clean | gzip -c > ${BACKUP_DIR}/${FILENAME}_all.gz
+# Find and clean up files whose modification time is greater than 30 days in the backup directory
+find ${BASE_DIR}/ -mtime +30 -exec rm -rf {} \;
+
+```
+
+- execute backup script
+
+```shell
+
+bash backup.sh
+
+```
+
+- find backup file
+
+```shell
+
+cd /data/pgsql-dump/
+
+```
+
+- copy database backup file to local
+
+```shell
+
+kubectl cp cluster-sample-ns/postgresql-cluster-sample-ns-ghostbaby-rs-0:/data/pgsql-dump/20210430/1423/pgsql-dump_all.gz ~/pgsql-dump_all.gz
+
+```