与Oracle相比，其他开源软件基本都未自带物理备份软件或者功能不够完整，要实现物理备份需借助三方插件完成。Postgresql虽然自带pg_basebackup，但是不支持增量备份。pg_rman是pgsql众多三方备份插件之一，其支持全量备份、增量备份、归档备份等，其功能类似oraclerman。
pg_rman下载地址:https://github.com/ossc-db/pg_rman/releases,下载对应pg版本的rpm文件或者源码包文件。rpm或者源码编译均依赖于zlib-devel包，所以需提前安装。
源码安装方法如下：
make
makeinstall
makeinstallcheck
pg数据库要进行物理备份，跟oracle一样，需开启归档功能，操作步骤如下：
altersystem set wal_level='replica';
altersystem set archive_mode='on';
altersystem set archive_command = 'cp %p .../archive/%f';
重启数据库。
开始备份前，还需进行catalog初始化，用于保存备份信息，类似oracle控制文件或者catalog里保留的备份信息，命令如下：
pg_rmaninit -B backup
[postgres@guassdb1~]$ pg_rman init
WARNING:ARCLOG_PATH is not set yet
DETAIL:The archive_command is not set in postgresql.conf.
HINT:Please set ARCLOG_PATH in pg_rman.ini or environmental variable.
INFO:SRVLOG_PATH is set to '/data/pgdata1/pg_log'
完成catalog初始化后，即可开始数据库备份。值得说明的是在catalog中有pg_rman.ini文件，可配置备份的环境变量、备份选项、备份集保留期限等信息，其功能类似oraclerman 的configure和showall。
pg_rman.ini示例：
[postgres@spcl-****:spc**_back]$cat pg_rman.ini
ARCLOG_PATH='/backup/s***dp_arch'
SRVLOG_PATH='/data/s***dp_data/log'
1、数据库全备
[postgres@guassdb1backup]$ pg_rman backup -b full -A pg_archivelog
INFO:copying database files
INFO:copying archived WAL files
INFO:backup complete
INFO:Please execute 'pg_rman validate' to verify the files are correctlycopied.
[postgres@guassdb1backup]$ pg_rman show
=====================================================================
StartTime EndTime Mode Size TLI Status
=====================================================================
2020-10-2516:24:17 2020-10-25 16:24:20 FULL 95MB 1 DONE
---由上面红色字体可看出备份成功后，其状态是done，还需要进行validate操作后，备份集才可用于恢复，增量备份才会用于做对比。
[postgres@guassdb1~]$ pg_rman validate
INFO:validate: "2020-10-25 16:24:17" backup and archive logfiles by CRC
INFO:backup "2020-10-25 16:24:17" is valid
[postgres@guassdb1~]$
[postgres@guassdb1~]$
[postgres@guassdb1~]$
[postgres@guassdb1~]$ pg_rman show detail
======================================================================================================================
StartTime EndTime Mode Data ArcLog SrvLog Total Compressed CurTLI ParentTLI Status
======================================================================================================================
2020-10-2516:24:17 2020-10-25 16:24:20 FULL 41MB 67MB ---- 95MB false 1 0 OK
--validate校验完成后，其备份集状态变成OK
备份完成后备份集文件的目录结构如下：
2、增量备份
pg_rmanbackup -b incremental -A pg_archivelog
在生产环境中，需制定备份策略，通常每周全备，每天增量，同时备份归档日志，备份脚本示例：
每周日全备，其他时间进行增量备份
#/bin/bash
.~/.bash_profile
current_path=`dirname$0`
exportPGPASSWORD='*****'
exportBACKUP_PATH=/backup***_back
LOCAL_HOST='**.**.**.**'
LOCAL_PORT=5432
BACK_DAY=6
#主库角色备份
master_backup(){
echo"master_backup"
pg_rmanbackup --backup-mode=$1 -Z -F -h ${LOCAL_HOST} -p ${LOCAL_PORT}--with-serverlog --keep-srvlog-days=7 --keep-data-generations=1--keep-arclog-files=100 --keep-arclog-days=1 -U postgres -Pv
#写入文件短信告警
if[[ $? -ne 0 ]]; then
echo`date '+%y-%m-%d %H:%M:%S': ` $1 "backup failed!" >${current_path}/backupflag
else
echo`date '+%y-%m-%d %H:%M:%S': ` $1 "backup successful!" >${current_path}/backupflag
pg_rmanvalidate
pg_rmanpurge
fi
}
#从库角色备份
slave_backup(){
echo"slave_backup"
pg_rmanbackup --backup-mode=$1 -Z -F -h $2 -p $3--standby-host=${LOCAL_HOST} --standby-port=${LOCAL_PORT}--with-serverlog --keep-srvlog-days=7 --keep-data-generations=1--keep-arclog-files=100 --keep-arclog-days=1 -U postgres -Pv
#写入文件短信告警
if[[ $? -ne 0 ]]; then
echo`date '+%y-%m-%d %H:%M:%S': ` $1 "backup failed!" >${current_path}/backupflag
else
echo`date '+%y-%m-%d %H:%M:%S': ` $1 "backup successful!" >${current_path}/backupflag
pg_rmanvalidate
pg_rmanpurge
fi
}
#判断日期,如周六全备,其它时间备份归档,若没有全量备份，则做全量备份
fullback_stat=`pg_rmanshow |grep "FULL"|awk '{print $8}'`
weekday=`date+%w`
if[[ ${fullback_stat} =~ "OK" ]]; then
if[[ ${weekday} -eq ${BACK_DAY} ]]; then
back_mode='full'
else
back_mode='incremental'
fi
else
back_mode='full'
fi
#数据库进程情况
is_alive=`pg_isready-p ${LOCAL_PORT}|grep "accepting"|wc -l`
if[[ $is_alive -eq 0 ]]; then
echo"database is down"
else
#主从
is_recovery=`psql-t -c "SELECT pg_is_in_recovery();"`
echo${is_recovery}
if[[ ${is_recovery} =~ "t" ]]; then
masterhost=`psql-t -c "select sender_host from pg_stat_wal_receiver;"`
masterport=`psql-t -c "select sender_port from pg_stat_wal_receiver;"`
logger-i "slave_backup will be running"
slave_backup${back_mode} ${masterhost} ${masterport}
else
logger-i "master_backup will be running"
master_backup${back_mode}
fi
fi
