在测试外部表的时候，因为修改了参数，所以需要greenplum重启加载，但是greenplum启动失败，如下所示：

[gpadmin@dwhm01_2_111 etc]$ tail -f /data/master/gpseg-1/pg_log/startup.log
2017-05-12 18:02:39.220978 CST,,,p26115,th1749395232,,,,0,,,seg-1,,,,,"LOG","00000","transaction files using default pg_system filespace",,,,,,,,"primaryMirrorPopulateFilespaceInfo","primary_mirror_mode.c",2619,
2017-05-12 18:13:13.134180 CST,,,p27033,th-337799392,,,,0,,,seg-1,,,,,"LOG","00000","removing all temporary files",,,,,,,,"RemovePgTempFiles","fd.c",1873,
2017-05-12 18:13:13.135226 CST,,,p27033,th-337799392,,,,0,,,seg-1,,,,,"LOG","00000","temporary files using default filespace",,,,,,,,"primaryMirrorPopulateFilespaceInfo","primary_mirror_mode.c",2559,
2017-05-12 18:13:13.135587 CST,,,p27033,th-337799392,,,,0,,,seg-1,,,,,"LOG","00000","transaction files using default pg_system filespace",,,,,,,,"primaryMirrorPopulateFilespaceInfo","primary_mirror_mode.c",2619,
2017-05-12 18:24:44.831946 CST,,,p28024,th1559271200,,,,0,,,seg-1,,,,,"LOG","00000","removing all temporary files",,,,,,,,"RemovePgTempFiles","fd.c",1873,
2017-05-12 18:24:44.833963 CST,,,p28024,th1559271200,,,,0,,,seg-1,,,,,"LOG","00000","temporary files using default filespace",,,,,,,,"primaryMirrorPopulateFilespaceInfo","primary_mirror_mode.c",2559,
2017-05-12 18:24:44.834277 CST,,,p28024,th1559271200,,,,0,,,seg-1,,,,,"LOG","00000","transaction files using default pg_system filespace",,,,,,,,"primaryMirrorPopulateFilespaceInfo","primary_mirror_mode.c",2619,
2017-05-15 09:27:28.689882 CST,,,p6189,th1917667104,,,,0,,,seg-1,,,,,"LOG","00000","removing all temporary files",,,,,,,,"RemovePgTempFiles","fd.c",1873,
2017-05-15 09:27:28.690914 CST,,,p6189,th1917667104,,,,0,,,seg-1,,,,,"LOG","00000","temporary files using default filespace",,,,,,,,"primaryMirrorPopulateFilespaceInfo","primary_mirror_mode.c",2559,
2017-05-15 09:27:28.691234 CST,,,p6189,th1917667104,,,,0,,,seg-1,,,,,"LOG","00000","transaction files using default pg_system filespace",,,,,,,,"primaryMirrorPopulateFilespaceInfo","primary_mirror_mode.c",2619,
20170515:09:37:30:006179 gpstart:dwhm01_2_111:gpadmin-[CRITICAL]:-Failed to start Master instance in admin mode
20170515:09:37:30:006179 gpstart:dwhm01_2_111:gpadmin-[CRITICAL]:-Error occurred: non-zero rc: 1
 Command was: 'env GPSESSID=0000000000 GPERA=None $GPHOME/bin/pg_ctl -D /data/master/gpseg-1 -l /data/master/gpseg-1/pg_log/startup.log -w -t 600 -o " -p 5432 -b 1 -z 0 --silent-mode=true -i -M master -C -1 -x 6 -c gp_role=utility " start'
rc=1, stdout='waiting for server to start........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... stopped waiting
', stderr='pg_ctl: could not start server
Examine the log output.
'


^C
[1]+  Exit 2                  gpstart  (wd: ~)
(wd now: /data/greenplum-db/etc)
[gpadmin@dwhm01_2_111 etc]$ 

Google了下，发现是由于配置错误导致的，把下面的配置配置在pg_hba.conf里面

gp_external_enable_exec = on # enable external tables with EXECUTE.
gp_external_grant_privileges = on #enable create http/gpfdist for non su’s

正确的是把gp_external_enable_exec、gp_external_grant_privileges配置在/data/greenplum-db-4.3.12.0/gpconfig/gpinitsystem_config里面。然后重新启动greenplum集群，就OK了，能启动起来了。