关于servlet执行系统命令的权限问题
我再linux下启动了tomcat服务器，其中一个servlet会执行linux系统命令，当客户端访问这个servlet时，servlet会用什么用户来执行linux系统命令？能否有程序控制使用指定用户？
谢谢

------解决方案--------------------
怕了你了。这是postgres的起动脚本，以postgres用户身份起动。你可以参考一下。
#! /bin/sh

# chkconfig: 2345 98 02
# description: PostgreSQL RDBMS

# This is an example of a start/stop script for SysV-style init, such
# as is used on Linux systems. You should edit some of the variables
# and maybe the 'echo ' commands.
#
# Place this file at /etc/init.d/postgresql (or
# /etc/rc.d/init.d/postgresql) and make symlinks to
# /etc/rc.d/rc0.d/K02postgresql
# /etc/rc.d/rc1.d/K02postgresql
# /etc/rc.d/rc2.d/K02postgresql
# /etc/rc.d/rc3.d/S98postgresql
# /etc/rc.d/rc4.d/S98postgresql
# /etc/rc.d/rc5.d/S98postgresql
# Or, if you have chkconfig, simply:
# chkconfig --add postgresql
#
# Proper init scripts on Linux systems normally require setting lock
# and pid files under /var/run as well as reacting to network
# settings, so you should treat this with care.

# Original author: Ryan Kirkpatrick <pgsql@rkirkpat.net>

# $PostgreSQL: pgsql/contrib/start-scripts/linux,v 1.7 2004/10/01 18:30:21 tgl Exp $

## EDIT FROM HERE

# Installation prefix
prefix=/app/pgsql

# Data directory
PGDATA= "/app/pgsql/data "

# Who to run the postmaster as, usually "postgres ". (NOT "root ")
PGUSER=postgres

# Where to keep a log file
PGLOG= "$PGDATA/serverlog "

## STOP EDITING HERE

# Check for echo -n vs echo \c
if echo '\c ' | grep -s c > /dev/null 2> &1 ; then
ECHO_N= "echo -n "
ECHO_C= " "
else
ECHO_N= "echo "
ECHO_C= '\c '
fi

# The path that is to be used for the script
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# What to use to start up the postmaster (we do NOT use pg_ctl for this,
# as it adds no value and can cause the postmaster to misrecognize a stale
# lock file)
DAEMON= "$prefix/bin/postmaster "

# What to use to shut down the postmaster
PGCTL= "$prefix/bin/pg_ctl "

set -e

# Only start if we can find the postmaster.
test -x $DAEMON || exit 0

# Parse command line parameters.
case $1 in
start)
$ECHO_N "Starting PostgreSQL: "$ECHO_C
su - $PGUSER -c "$DAEMON -D '$PGDATA ' & " > > $PGLOG 2> &1
echo "ok "
;;
stop)
echo -n "Stopping PostgreSQL: "
su - $PGUSER -c "$PGCTL stop -D '$PGDATA ' -s -m fast "
echo "ok "
;;
restart)
echo -n "Restarting PostgreSQL: "
su - $PGUSER -c "$PGCTL stop -D '$PGDATA ' -s -m fast -w "
su - $PGUSER -c "$DAEMON -D '$PGDATA ' & " > > $PGLOG 2> &1
echo "ok "
;;
reload)
echo -n "Reload PostgreSQL: "
su - $PGUSER -c "$PGCTL reload -D '$PGDATA ' -s "
echo "ok "
;;
status)
su - $PGUSER -c "$PGCTL status -D '$PGDATA ' "
;;
*)
# Print help
echo "Usage: $0 {start|stop