Auto set postgresql shared_buffers to fraction of available memory

pg_auto_shared_buffers.sh

#!/bin/bash

## Adjust shared_buffer size for system (25% of available)
SYS_MEM=`cat /proc/meminfo | grep MemTotal | sed "s/[^0-9]//g"`
PG_MEM=`echo $(( $SYS_MEM / 4 ))`
RE="s/##PG_MEM##/$PG_MEM/g"

## Substitute shared_buffers in your config with ##PG_MEM##
## e.g: shared_buffers = ##PG_MEM##kB

sed -i $RE postgresql.conf