Postgresql连接失败和设置系统shmmax的方法

shaoqin

　　昨天我在远程连接postgres数据库时遇到这样的错误：

psql: could not connect to server: Connection refused
Is the server running on host "my host name" (IP) and accepting
TCP/IP connections on port 5432?
　　于是我修改了postgresql.conf: 

listen_addresses = '*'
　　 在pg_hba.conf， 添加了我的IP，如下：

#for n/w access
host    all         c2d         10.147.16.0/24        md5
　　后来查了些资料才知道要修改postgresql.conf，修改listen_addresses = '*' 对所有的地址都监听，同时修改缓存为7G，restart postgres后又遇到了一些错误：

2015-05-14 09:39:00 CST FATAL:  could not create shared memory segment: Invalid argument
2015-05-14 09:39:00 CST DETAIL:  Failed system call was shmget(key=5432001, size=7709171712, 03600).
2015-05-14 09:39:00 CST HINT:  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 7709171712 bytes), reduce PostgreSQL's shared memory usage, perhaps by reducing shared_buffers or max_connections.
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.
　　这是要求修改系统的SHMMAX， 我的解决办法如下：

# view current shmmax size
$more /proc/sys/kernel/shmmax
# change the size temporarily to 8G
$sudo su
$sudo echo 8589934592 > /proc/sys/kernel/shmmax
# change the size temporarily
$ sudo vim /etc/sysctl.conf
append the line: kernel.shmmax = 8589934592
　　 
　　当然这里配置的是8G，我psql用到的是7G，修改一下就可以了。