问题环境：
在centos6上搭建单机Oracle10G，搭建完成关机后启动报错，报错信息如下：
[root@centos6 ~]# su - oracle
[oracle@centos6 ~]$ sqlplus / as sysdba
SQL> startup;
ORA-27125: unable to create shared memory segment
Linux-x86_64 Error: 1: Operation not permitted
SQL> DisconnectedORA-27125: unable to create shared memory segment
Linux-x86_64 Error: 1: Operation not permitted
系统版本：centos6.8
数据库版本： Release 10.2.0.1.0
分析：
根源在于Linux的错误，系统因权限等问题不被允许，所以数据库无法创建共享内存段。在创建共享内存段的时候需要使用到hugepage，系统会进行权限限制。
解决方法：
临时方案：查询dba组的组ID，加入到系统内核中，如下：
[oracle@centos6 ~]$ id oracle
uid=500(oracle) gid=500(oinstall) groups=500(oinstall),501(dba)
# 切换为root用户进行添加
[root@centos6 ~]# echo 501 > /proc/sys/vm/hugetlb_shm_group重新启动数据库
[root@centos6 ~]# su - oracle
[oracle@centos6 ~]$ sqlplus / as sysdba
SQL> startup;
ORACLE instance started.
Total System Global Area 595591168 bytes
Fixed Size 2022568 bytes
Variable Size 180355928 bytes
Database Buffers 406847488 bytes
Redo Buffers 6365184 bytes
Database mounted.
Database opened.临时方案，在系统重启后会失效，永久更改的方法如下
永久方案：修改内核参数文件
[root@centos6 ~]# echo "vm.hugetlb_shm_group = 501" >> /etc/sysctl.conf
[root@centos6 ~]# sysctl -p
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
kernel.shmall = 2097152
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default = 4194304
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 262144
vm.hugetlb_shm_group = 501