场景：普通用户编译的apache,要在该用户下启动1024端口以下的apache端口
1、假设普通用户为sims20,用该用户编译 安装了一个apache,安装路径为/opt/aspire/product/sims20/apache
./configure --prefix=/opt/aspire/product/sims20/apache --enable-so --enable-modules=all --enable-mods-shared=all --enable-mods-shared='proxy proxy_ajp proxy_balancer proxy_connect proxy_ftp proxy_http proxy_rewrite'
make
make install
2、编译完成后，设置http.conf的监听端口为80
3、直接用普通用户sims20启动
[sims20@bcd-app01 bin]$ ./apachectl start
(13)Permission denied: make_sock: could not bind to address [::]:80
(13)Permission denied: make_sock: could not bind to address 0.0.0.0:80
no listening sockets available, shutting down
Unable to open logs
出错原因：在linux下，普通用户只能用1024以上的端口，而1024以内的端口只能由root用户才可以使用
4、利用setuid来解决问题，这样使用httpd能以root权限运行
用root用户登录，进入/opt/aspire/product/sims20/apache/bin，分别用chown root httpd、chmod u+s httpd 设置httpd的属主为root及特殊权限
[root@bcd-app01 bin]# ls -l httpd
-rwxr-xr-x 1 sims20 aspire 3517470 3月 15 17:12 httpd
[root@bcd-app01 bin]# chown root httpd
[root@bcd-app01 bin]# ls -l httpd
-rwxr-xr-x 1 root aspire 3517470 3月 15 17:12 httpd
[root@bcd-app01 bin]# chmod u+s httpd
[root@bcd-app01 bin]# ls -l httpd
-rwsr-xr-x 1 root aspire 3517470 3月 15 17:12 httpd
5、重新进入普通用户sims20,启动apache
[sims20@bcd-app01 bin]$ ./apachectl start
可以正常启动，没报错
6、试着访问一下
[sims20@bcd-app01 bin]$ curl http://10.24.12.159:80
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>403 Forbidden</title>
</head><body>
<h1>Forbidden</h1>
<p>You don't have permission to access /
on this server.</p>
</body></html>
报403 Forbidden错误
7、看一下进程
[sims20@bcd-app01 bin]$ ps -ef |grep httpd
root 7841 1 0 17:24 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
daemon 7844 7841 0 17:24 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
daemon 7845 7841 0 17:24 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
daemon 7846 7841 0 17:24 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
daemon 7847 7841 0 17:24 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
daemon 7848 7841 0 17:24 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
sims20 8006 3026 0 17:29 pts/4 00:00:00 grep httpd
怎么跑出daemon 用户了， 原来httpd主进程仍然以root用户的权限运行，而它的子进程将以一个较低权限的用户运行 ，而这个较低权限用户daemon 在http.conf中配置
7、在http.conf中配置一下，将用户改成root
User daemon
Group daemon
改成
User root
Group root
8、再次用普通用户启动apache
[sims20@bcd-app01 bin]$ ./apachectl restart
Syntax error on line 76 of /opt/aspire/product/sims20/apache/conf/httpd.conf:
Error:\tApache has not been designed to serve pages while\n\trunning as root. There are known race conditions that\n\twill allow any local user to read any file on the system.\n\tIf you still desire to serve pages as root then\n\tadd -DBIG_SECURITY_HOLE to the CFLAGS env variable\n\tand then rebuild the server.\n\tIt is strongly suggested that you instead modify the User\n\tdirective in your httpd.conf file to list a non-root\n\tuser.\n
不行的，要重新加参数编译
9、再次修改在http.conf中配置一下，将用户改成普通用户吧
改成
User sims20
Group aspire
10、再次用普通用户sims20启动apache
[sims20@bcd-app01 bin]$ ./apachectl start
[sims20@bcd-app01 bin]$ ps -ef |grep httpd
root 9720 1 0 18:09 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
sims20 9721 9720 0 18:09 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
sims20 9722 9720 0 18:09 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
sims20 9723 9720 0 18:09 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
sims20 9724 9720 0 18:09 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
sims20 9725 9720 0 18:09 ? 00:00:00 /opt/aspire/product/sims20/apache/bin/httpd -k start
sims20 9739 3026 0 18:09 pts/4 00:00:00 grep httpd
6、试着访问一下
[sims20@bcd-app01 bin]$ curl http://10.248.12.159:80
<html><body><h1>It works!</h1></body></html>
成功了