当我们执行cobbler check时，出现这种错误：httpd does not appear to be running and proxying cobbler, or SELinux is in the way.

具体情况：

ttpd does not appear to be running and proxying cobbler, or SELinux is in the way. Original traceback:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/cobbler/cli.py", line 251, in check_setup
    s.ping()
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1233, in __call__
    return self.__send(self.__name, args)
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1587, in __request
    verbose=self.__verbose
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1273, in request
    return self.single_request(host, handler, request_body, verbose)
  File "/usr/lib64/python2.7/xmlrpclib.py", line 1321, in single_request
    response.msg,
ProtocolError: <ProtocolError for 127.0.0.1:80/cobbler_api: 503 Service Unavailable>

解决方法如下：

[root@centos7 ~]# getenforce 
Enforcing
[root@centos7 ~]# setenforce 0
[root@centos7 ~]# getenforce 
Permissive
[root@centos7 ~]# systemctl  restart httpd.service  #重启http服务
[root@centos7 ~]# cobbler check
The following are potential configuration items that you may want to fix:


1 : The 'server' field in /etc/cobbler/settings must be set to something other than localhost, or kickstarting features will not work.  This should be a resolvable hostname or IP for the boot server as reachable by all machines that will use it.
2 : For PXE to be functional, the 'next_server' field in /etc/cobbler/settings must be set to something other than 127.0.0.1, and should match the IP of the boot server on the PXE network.
3 : SELinux is enabled. Please review the following wiki page for details on ensuring cobbler works correctly in your SELinux environment:
    https://github.com/cobbler/cobbler/wiki/Selinux
4 : change 'disable' to 'no' in /etc/xinetd.d/tftp
5 : Some network boot-loaders are missing from /var/lib/cobbler/loaders, you may run 'cobbler get-loaders' to download them, or, if you only want to handle x86/x86_64 netbooting, you may ensure that you have installed a *recent* version of the syslinux package installed and can ignore this message entirely.  Files in this directory, should you want to support all architectures, should include pxelinux.0, menu.c32, elilo.efi, and yaboot. The 'cobbler get-loaders' command is the easiest way to resolve these requirements.
6 : enable and start rsyncd.service with systemctl
7 : debmirror package is not installed, it will be required to manage debian deployments and repositories
8 : The default password used by the sample templates for newly installed machines (default_password_crypted in /etc/cobbler/settings) is still set to 'cobbler' and should be changed, try: "openssl passwd -1 -salt 'random-phrase-here' 'your-password-here'" to generate new one
9 : fencing tools were not found, and are required to use the (optional) power management features. install cman or fence-agents to use them


Restart cobblerd and then run 'cobbler sync' to apply changes.

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