# PostgreSQL Backups

Sentinel is using PostgreSQL database for all analytics/reports/history data. PostgreSQL should be done on regular bases to eliminate possible data losses in case of disasters.

## Standalone Hot Backup

This is the standalone backups which provide fast and consistent data snapshot. These are backups that cannot be used for point-in-time recovery, yet are typically much faster to backup and restore than `pg_dump` dumps. This backups can not be used for PostgreSQL version migration and can created and restored only on the same major version. 

#### Create standalone hot backup

Create folder for backups

```bash
mkdir /data/pg_backup/
chown postgres:postgres /data/pg_backup/
```

Run command to create backup:

```bash
sudo -u postgres pg_basebackup -P -Ft -z -Z4 -v -Xs -R -D /data/pg_backup/$(date +"+%Y-%m-%d")/
```

On finish this command will create hot backup of the PostgreSQL cluster. It will create folder with current date which will have two files `base.tar.gz` and `pg_wal.tar.gz`

#### Restore hot backup

Assuming following

* `postgres-snt` - PostgreSQL service name for Sentinel,
* `/opt/pdgata/` - PostgreSQL data directory specified as `PGDATA`,
* `/data/pg_backup/2022-11-07` - Folder with backup which be restored.

Create folder for PostgreSQL and ensure that its empty:

```bash
mkdir -p /opt/pgdata/
rm -rf /opt/pgdata/*
```

Extract data in this folder from preferred backup

```bash
tar xvf /data/pg_backup/2022-11-07/base.tar.gz -C /opt/pgdata/
tar xvf /data/pg_backup/2022-11-07/pg_wal.tar.gz -C /opt/pgdata/pg_wal/
```

Ensure valid permissions is set

```bash
chown -R postgres:postgres /opt/pgdata
chmod -R 0700 /opt/pgdata
```

Restart your PostgreSQL service

```bash
systemctl restart postgres-snt
```

Connect to database and check status:

```bash
sudo -u postgres psql sentinel
```

Run to check status:

```sql
SELECT pg_is_in_recovery();
> t
SELECT pg_promote();
> t
SELECT pg_is_in_recovery();
> f
```

PostgreSQL cluster is ready to be used and Sentinel service can be started.

<br>

<br>


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