[Pdns-users] Pipebackend can't run backend

Dan Campbell - dan@us.ibm.com dan at us.ibm.com
Thu Jan 21 22:59:56 UTC 2021

The script does have a shebang line and it runs fine from  the command line.

It also work it I run “pdns_server –daemon=no”

I checked, and the VM does have SELinux, which was set to permissive mode by default. I disabled SELinux and rebooted.  It didn’t help.

Thanks for the suggestion, though. I didn’t know to check for that.

Dan Campbell

From: Brian Candler <b.candler at pobox.com>
Date: Thursday, January 21, 2021 at 2:07 PM
To: "Dan Campbell - dan at us.ibm.com" <dan at us.ibm.com>, "pdns-users at mailman.powerdns.com" <pdns-users at mailman.powerdns.com>
Subject: [EXTERNAL] Re: [Pdns-users] Pipebackend can't run backend

On 21/01/2021 20:48, Dan Campbell - dan--- via Pdns-users wrote:...
This Message Is From an External Sender

This message came from outside your organization.

On 21/01/2021 20:48, Dan Campbell - dan--- via Pdns-users wrote:
I just installed the Authoritative server 4.4.0 on a CentOS 8 virtual machine and I’m trying to get a simple pipebackend running.

The backend is a python script that runs from the command line, but pdns_server fails to start and give the following error:

[PIPEBackend] Unable to launch, fatal argument error: Command '/home/webapps/dns/bin/backend.py' cannot be executed: Permission>
Caught an exception instantiating a backend: Command '/home/webapps/dns/bin/backend.py' cannot be executed: Permission denied
Cleaning up
Distributor caught fatal exception: Command '/home/webapps/dns/bin/backend.py' cannot be executed: Permission denied

The permissions on the script and all directories in the path are 755 …

Any ideas about why pdns_server (running under the pdns id) does not have permissions to run a program with 755 permissions?

If it has a shebang line and you can run it directly from the command line by typing "/home/webapps/dns/bin/backend.py", then my guess is that it's an SELinux or AppArmor thing.

Being CentOS then it would be SELinux.  Try switching SELinux into permissive mode and see if that makes it work.  If it does, have fun tweaking SELinux policies :-)


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