某日开发反馈测试环境的集群启动失败
报错内容如下：
[gpadmin@hadoop-test2:/root]$ gpstart20181205:16:42:23:005451 gpstart:hadoop-test2:gpadmin-[INFO]:-Starting gpstart with args: 20181205:16:42:23:005451 gpstart:hadoop-test2:gpadmin-[INFO]:-Gathering information and validating the environment...20181205:16:42:23:005451 gpstart:hadoop-test2:gpadmin-[INFO]:-Greenplum Binary Version: 'postgres (Greenplum Database) 5.0.0 build dev'20181205:16:42:23:005451 gpstart:hadoop-test2:gpadmin-[INFO]:-Greenplum Catalog Version: '301705051'20181205:16:42:24:005451 gpstart:hadoop-test2:gpadmin-[INFO]:-Starting Master instance in admin mode20181205:16:52:24:005451 gpstart:hadoop-test2:gpadmin-[CRITICAL]:-Failed to start Master instance in admin mode20181205:16:52:24:005451 gpstart:hadoop-test2:gpadmin-[CRITICAL]:-Error occurred: non-zero rc: 1 Command was: 'env GPSESSID=0000000000 GPERA=None $GPHOME/bin/pg_ctl -D /home/gpadmin/gpdata/gpmaster/gpseg-1 -l /home/gpadmin/gpdata/gpmaster/gpseg-1/pg_log/startup.log -w -t 600 -o " -p 2346 --gp_dbid=1 --gp_num_contents_in_cluster=0 --silent-mode=true -i -M master --gp_contentid=-1 -x 0 -c gp_role=utility " start'rc=1, stdout='waiting for server to start........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... stopped waiting', stderr='could not change directory to "/root"pg_ctl: could not start serverExamine the log output.查看启动日志发现：
vim /home/gpadmin/gpdata/gpmaster/gpseg-1/pg_log/startup.log2018-12-05 08:42:24.067241 GMT,,,p5464,th-829482944,,,,0,,,seg-1,,,,,"WARNING","01000","""work_mem"": setting is deprecated, and may be removed in a future release.",,,,,,,,"set_config_option","guc.c",4666,2018-12-05 08:42:24.067612 GMT,,,p5464,th-829482944,,,,0,,,seg-1,,,,,"WARNING","01000","""work_mem"": setting is deprecated, and may be removed in a future release.",,,,,,,,"set_config_option","guc.c",4666,2018-12-05 08:42:24.083813 GMT,,,p5465,th-829482944,,,,0,,,seg-1,,,,,"LOG","00000","removing all temporary files",,,,,,,,"RemovePgTempFiles","fd.c",2046,2018-12-05 08:42:24.098673 GMT,,,p5465,th-829482944,,,,0,,,seg-1,,,,,"FATAL","XX000","could not create shared memory segment: Invalid argument (pg_shmem.c:183)","Failed system call was shmget(key=2346001, size=177586016, 03600).","This error usually means that PostgreSQL's request for a shared memory segment exceeded your kernel's SHMMAX parameter. You can either reduce the request size or reconfigure the kernel with larger SHMMAX. To reduce the request size (currently 177586016 bytes), reduce PostgreSQL's shared_buffers parameter (currently 4000) and/or its max_connections parameter (currently 253).If the request size is already small, it's possible that it is less than your kernel's SHMMIN parameter, in which case raising the request size or reconfiguring SHMMIN is called for.The PostgreSQL documentation contains more information about shared memory configuration.",,,,,,"InternalIpcMemoryCreate","pg_shmem.c",183,1内容大概是说/etc/sysctl.conf设置的内核参数shmmax过小，导致启动失败
查看/etc/sysctl.conf下的配置发现：
kernel.shmmax = 20000000kernel.shmmni = 4096kernel.shmall = 40000000kernel.sem = 250 512000 100 2048kernel.sysrq = 1kernel.core_uses_pid = 1kernel.msgmnb = 65536kernel.msgmax = 65536kernel.msgmni = 2048net.ipv4.tcp_syncookies = 1net.ipv4.ip_forward = 0net.ipv4.conf.default.accept_source_route = 0net.ipv4.tcp_tw_recycle = 1net.ipv4.tcp_max_syn_backlog = 4096net.ipv4.conf.all.arp_filter = 1net.ipv4.ip_local_port_range = 1025 65535net.core.netdev_max_backlog = 10000net.core.rmem_max = 2097152net.core.wmem_max = 2097152vm.overcommit_memory = 2对比官网建议的设置和参数定义以及集群已有的数据量，发现确实过小。于是改成官网建议的设置后启动。
20181205:17:54:28:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-----------------------------------------------------20181205:17:54:28:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-Successful segment starts= 820181205:17:54:28:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-Failed segment starts= 020181205:17:54:28:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-Skipped segment starts (segments are marked down in configuration)= 020181205:17:54:28:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-----------------------------------------------------20181205:17:54:28:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-Successfully started 8 of 8 segment instances 20181205:17:54:28:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-----------------------------------------------------20181205:17:54:28:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-Starting Master instance hadoop-test2 directory /home/gpadmin/gpdata/gpmaster/gpseg-1 20181205:17:54:29:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-Command pg_ctl reports Master hadoop-test2 instance active20181205:17:54:29:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-No standby master configured. skipping...20181205:17:54:29:009711 gpstart:hadoop-test2:gpadmin-[INFO]:-Database successfully started启动成功。
总结：pg启动相关的内核参数配置与实际情况不匹配时，会导致启动失败。可通过查看日志详细信息查找根源解决问题。
参考文档：
1、官网建议设置 http://gpdb.docs.pivotal.io/4380/prep_os-system-params.html#topic3
2、内核参数含义http://www.oicqzone.com/pc/2012091612901.html