Issue Backup Manager - DNS resolution problem

[Webbenny]

Hello community,

I want to setup a remote ftp storage for plesk backups. I've the same configuration already succcessfull running on another server. So this is a bit strange....

Under FTP Storage Settings I insert the servername which is NOT the local hostname and also the user credentials. Then I confirm with OK. After that the error:

Using the local Plesk's FTP server as a remote storage is prohibited. Please specify a remote location.

appears. I've found no entries in the /var/log/plesk/panel.log and /usr/local/psa/PMM/logs/pmmcli.log.
The system DNS resoltions is fine (tested with curl and dig). And setting up the remote location with IP works also,. (but I wnat to use a dynamic). So how can I fix plesks wrong dns resolution? I thought Plesk uses the system resolution?!

 

[MyDomainLabs]

To set configure the Plesk Server you are currently logged into so that it can store Plesk FTP backups sent from another Plesk server please review the steps listed below:

1.) Select Settings & Tools from main navigation menu on the left hand side of Plesk. (Under Server Management using Service Provider View)
2.) Locate the Category: Tools & Resources then Select Backup Manager.
3.) Click Settings then mark the check box option "Allow setting up FTP backup storage on the local server."

 

[Webbenny]

Sorry, but you didn't read the question.. I want to use a Backup localtion on a external server:

Under FTP Storage Settings I insert the servername which is NOT the local hostname and also the user credentials.

I works by IP but not by Domainname. So the question is how does Plesk resolve domain names? Because this answer must be different to system tools like dig or curl..

 

[Bitpalast]

Please check wether the "external" domain name is listed in your local DNS (bind) server. If that is the case, it might not apply to the Internet, but your local server will resolve it to its own IP, hence think that you are trying to do the local backup.

 

[Webbenny]

Thank you for your reply. Hmm.. The external domain is <myid>.myfritz.net if i check

dig <myid>.myfritz.net @127.0.0.1

I got the correct IP back. So bind should resolve it propper, or do you have another idea how to test it?

 

[Bitpalast]

Please make sure that the domain name you are using is not configured as a domain (or subscription) in Plesk.

 

[Webbenny]

No, this domain is not managed/configured within plesk.

 

[Bitpalast]

It is possible to use a dynamic domain name with backups.
You are not using the domain name that you have entered into the backup configuration as a hostname.
You are not using "localhost" as a domain name in the configuraton.
You are not using the domain name anywhere else on the system, e.g. not as a subscription name, nor a domain inside another subscription.
When you run "dig" on Linux and use the local DNS resolver, it resolves to the correct external address.

Nevertheless Plesk thinks, that the domain name is local.

Could you please post the content of /etc/resolv.conf here?
What type of server is this? Is this a dedicated server? A virtual machine? Because somewhere Plesk resolves the domain to its own IP.

 

[Webbenny]

Yes, I completely match your statements. It must be possible ;-). I'm using the same configuration without any problems on another virtual server with plesk.
Both machines ar hetzner virtual cloud server running Ubuntu 18.04.

# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "systemd-resolve --status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs must not access this file directly, but only through the
# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,
# replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.

nameserver 127.0.0.53
options edns0

Dig resolves anything proper. So thats why I'am wondering if plesk uses another DNS resolution?!

 

[Bitpalast]

Not that I'd know of any different resolution methods. The Plesk philosophy is to use all that the operating system provides and to provide a shell on top of it to make accessing the tools easier.

There are three guesses
- Somewhere in some Plesk table there are leftovers of the domain name in question. This could be found out by searching the psa database for the domain name.
- The Hetzner name servers are causing the issues as they sometimes do. You could try to change /etc/resolv.conf to only use 8.8.8.8 and 8.8.4.4 instead (at least for a test, it can then be changed back to the current state).
- The DynDNS service only forwards port 80 and port 443 requests and responds with 127.0.0.1 on other packets (very unlikely though).

 

[Webbenny]

Thank you for your reply!

- I tried: MariaDB [psa]> select * from domains; there is no data for the domain I want to use for backup.
- The second thing is: # dig xxxxxxxxxxxx.myfritz.net @127.0.0.1 resolves proper to my correct IP.
- The dynDNS is ok, I use this Backup location on another plesk machine both are running Plesk Onyx Version 17.8.11, and both are standing @hetzner (with the same resolv.conf). Thats really confusing...

 

[Bitpalast]

And have you tried the suggested change to resolv.conf?

 

[Bitpalast]

Another idea: Have you tried to
# ftp <username>@<dyndns-domain.tld>
or
# curl -v -P - --ssl -k -u <username> 'ftp://<dyndns-domain.tld>/'
from the Linux surface on your system? Does this connection work correctly? With this test you can exclude issues with a forwarding of FTP connections to your dynamic IP.

 

[Webbenny]

I've already tested with curl (see my first post)

The system DNS resoltions is fine (tested with curl and dig)

So tried it with changing the resolv.conf, to 8.8.8.8 and 8.8.4.4 (Googles) and 1.1.1.1 and 1.0.0.1 (Cloudflare).
Under both conditions the ftp and curl variant works (as before). But not the plesk backup. :-(.
For me it's clear that plesk doesn't use the system's DNS resolution tools for Backup tasks.

 

[Bitpalast]

Is the dynamic domain accessible and configured through IPv4 or only IPv6? It might not work when it only has an AAAA record, but not an A record.

 

[Webbenny]

No, it must work with only an AAAA record. I have the same plesk version setup and running with a AAAA-Domain only backup location..

 

[Webbenny]

So finally I got the evidence, something is happening wrong in the "black box".
I've done the backup for a domain manually:

/usr/local/psa/bin/pleskbackup --domains-id 1 --output-file=ftp://pwefom27wefklwm.myfritz.net --ftp-login=backup-ftp --ftp-password=********** -vvvvv

/opt/psa/PMM/sessions/2019-03-26-122059.717# cat migration.log  | grep "Curl"
[2019-03-26 12:22:41.793|20070] INFO: Curl output: * Data conn was not available immediately
[2019-03-26 12:22:41.793|20070] INFO: Curl output: * Checking for server connect
[2019-03-26 12:22:41.797|20070] INFO: Curl output: * Checking for server connect
[2019-03-26 12:22:41.797|20070] INFO: Curl output: * Ready to accept data connection from server
[2019-03-26 12:22:41.797|20070] INFO: Curl output: * Connection accepted from server
(...)
[2019-03-26 12:22:42.075|20070] INFO: Curl output: < 220 **** FTP server ready.
[2019-03-26 12:22:42.075|20070] INFO: Curl output: > USER backup-ftp
[2019-03-26 12:22:43.496|20070] INFO: Curl output: < 331 Password required for backup-ftp.
[2019-03-26 12:22:43.497|20070] INFO: Curl output: > PASS *****
[2019-03-26 12:22:43.545|20070] INFO: Curl output: < 230 User backup-ftp logged in.
[2019-03-26 12:22:43.545|20070] INFO: Curl output: > PWD
[2019-03-26 12:22:43.561|20070] INFO: Curl output: < 257 "/" is current directory.
(...)
[2019-03-26 12:22:43.649|20070] INFO: Curl output: * Connection accepted from server
[2019-03-26 12:24:44.391|20070] INFO: Curl output: * Remembering we are in dir ""
[2019-03-26 12:24:44.522|20070] INFO: Curl output: < 226 Transfer complete.
[2019-03-26 12:24:44.522|20070] INFO: Curl output: * Connection #0 to host pwefom27wefklwm.myfritz.net left intact

the backup runs proper, the file is stored in the ftp location

So dear plesk staff: What does the Plesk GUI do here? What's the issue of the

Using the local Plesk's FTP server as a remote storage is prohibited. Please specify a remote location.

message? From commandline it's all working great.

My assumption is, that there is any kind of wrong DNS resolution here.

 

[Bitpalast]

Please report a bug here: Reports