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**philou31** · 21-07-2024, 14:17

I've made a "flush hosts" on my MariaDB (SQL command line) after observing same issue with a bash script making DB request. This action solved my issue for the script but not for Zabbix: user "zabbix"@"serverC" doesn't work but user "zabbix"@"%" works. I would rather have "zabbix"@"serverC".

I noticed something in zabbix-server log: ==> cannot send list of active checks to "IP_SERVERC": host [SERVERB] not found

And this for 2 servers whose hostname I changed.
The new hostname for these 2 servers have been modified on Zabbix interface, checks are available without issue for days.

And when I have a look a the discovery result on Zabbix interface I can notice that these 2 severs are the only ones whitout their hostname ==> IP_SERVER (hostname) while the others have it.

So I really think it's a Zabbix issue, like cache or others (I sought everywhere in zabbix DB and I've not found anything with old servers name, only current servers name).

(I've created a DNS server on a VM for having a specific DNS and not my internet box. All my servers and my NAS actually use this DNS instead of my internet box. All works, locally or other.)

**Markku** · 21-07-2024, 15:37

Host IP configurations and agent hostname configurations inside Zabbix are not related to the DNS resolution happening inside the database service.

Good that you already found something that affected the DNS resolution on the database.

If you need further help, please lay out the exact and related current configurations and the error message information, maybe someone is able to help you further.

Also, now that you noticed some pecularities in the database DNS resolution, you could try the "zabbix@%" case again and then see the host cache, what does the database tell you about the resolved name. See: https://mariadb.com/kb/en/performanc...t_cache-table/

Markku

**Markku** · 21-07-2024, 15:54

One more thing: What was your own explanation, why didn't the "zabbix"@"ip-of-the-zabbix-server" permission case work when you tested it?

Markku

**philou31** · 21-07-2024, 17:07

The table "host_cache" is empty (following your link).
User "zabbix"@"ip-of-the-zabbix-server" doesn't work, like "zabbix"@"hostname-of-the-zabbix-server".

**Markku** · 21-07-2024, 17:13

Did you enable the performance schema? It is not enabled by default.

Yes you told that the IP address syntax didn't work, but did you find out why your database server doesn't accept your Zabbix server's IP address in the permissions? You haven't showed us any configurations so we are not seeing your attempts or any typos or other reasons for the otherwise correct configurations to not work in your setup.

Markku

**philou31** · 21-07-2024, 18:09

I have enable performance schema right now (it wasn't enabled).
And I see good relation with (good) hostname-zabbix-server and ip-zabbix-server on table "host_cache". And for all others servers.

What do you want to see as configuration?

**Markku** · 21-07-2024, 18:33

Originally posted by philou31

And I see good relation with (good) hostname-zabbix-server and ip-zabbix-server on table "host_cache". And for all others servers.

Again you don't show us anything, you just say that everything is fine

So, when you now give the Zabbix database user permissions based on the hostname that you see in the MariaDB host_cache (also removing all other Zabbix user permissions), is it working?

Originally posted by philou31

What do you want to see as configuration?

- Zabbix server+frontend IP address+netmask and OS hostname
- Zabbix server configurations (like sudo grep -v -E "^(#|$)" /etc/zabbix/zabbix_server.conf)
- Zabbix frontend configurations (like sudo grep \$DB /etc/zabbix/web/zabbix.conf.php)
- MariaDB server IP address+netmask and DNS resolver address(es)
- select * from mysql.db where user="zabbix"\G (assuming your Zabbix database username is "zabbix")
- /etc/hosts on the MariaDB server
- Reverse DNS resolution results for Zabbix server+frontend IP addresses using the DNS resolver(s)
- Information about how the DNS server/resolver is configured to know the IP+hostname mappings about the servers
- what else do you think we should know?

Plus, if you still have problems, I now third time ask you to provide the actual error messages with proper contexts (not just "I got error again" but what/where/how).

(you can obviously replace sensitive information with some other unique descriptive strings, like replace IP addresses with private IP addresses, keeping the netmasks to be able to see which hosts are in the same subnet and which are not)

Markku

**philou31** · 22-07-2024, 18:39

Originally posted by Markku

Again you don't show us anything, you just say that everything is fine

Screenshot of host_cache table:

Zabbix server name is fr-srvmonitor.

Originally posted by Markku

So, when you now give the Zabbix database user permissions based on the hostname that you see in the MariaDB host_cache (also removing all other Zabbix user permissions), is it working?

No it's not working because it's exactly what I've done in previous tests.

Originally posted by Markku

- Zabbix server+frontend IP address+netmask and OS hostname

Originally posted by Markku

- Zabbix server configurations (like sudo grep -v -E "^(#|$)" /etc/zabbix/zabbix_server.conf)

LogFile=/var/log/zabbix/zabbix_server.log
LogFileSize=0
PidFile=/run/zabbix/zabbix_server.pid
SocketDir=/run/zabbix
DBHost=DBSERV
DBName=zabbix
DBUser=zabbix
DBPassword=ABCDEF
DBPort=3307
AllowUnsupportedDBVersions=1
SNMPTrapperFile=/var/log/snmptrap/snmptrap.log
Timeout=4
AlertScriptsPath=/usr/lib/zabbix/alertscripts
FpingLocation=/usr/bin/fping
Fping6Location=/usr/bin/fping6
LogSlowQueries=3000
User=chkuser
StatsAllowedIP=127.0.0.1

Originally posted by Markku

- MariaDB server IP address+netmask and DNS resolver address(es)

Originally posted by Markku

- select * from mysql.db where user="zabbix"\G (assuming your Zabbix database username is "zabbix")

**Markku** · 22-07-2024, 19:28

AllowUnsupportedDBVersions=1

Is there some specific reason for this?

Markku

**Markku** · 23-07-2024, 08:00

modifying user "zabbix"@"%" to "zabbix"@"fr-srvmonitor"

If your DNS resolver returns the server name as an FQDN (bind usually does, but as mentioned, I don't see your images in the post), this server name "fr-srvmonitor" (without domain) won't work, based on the MySQL/MariaDB documentation. Unless of course there is a hosts file entry on the DB server for it.

Markku

**philou31** · 23-07-2024, 17:28

I've tried to copy/paste screenshots but I should cut my post in 2 posts.
2nd post:

Originally posted by Markku

- /etc/hosts on the MariaDB server

Originally posted by Markku

- Reverse DNS resolution results for Zabbix server+frontend IP addresses using the DNS resolver(s)

Originally posted by Markku

- Information about how the DNS server/resolver is configured to know the IP+hostname mappings about the servers

Using bind.
With 1 zone named "maison" with all servers & IP on it:

And another zone for reverse:

Originally posted by Markku

- what else do you think we should know?

Originally posted by Markku

Plus, if you still have problems, I now third time ask you to provide the actual error messages with proper contexts (not just "I got error again" but what/where/how).

(you can obviously replace sensitive information with some other unique descriptive strings, like replace IP addresses with private IP addresses, keeping the netmasks to be able to see which hosts are in the same subnet and which are not)

Markku

Here is the error message after modifying user "zabbix"@"%" to "zabbix"@"fr-srvmonitor" (action on zabbix interface is just to modify DNS name on the server):

Hostname "fr-srvsurv" was the old name of zabbix server, before become "fr-srvmonitor".

I hope you can see them now.

AllowUnsupportedDBVersions=1

Originally posted by Markku

Is there some specific reason for this?

Markku

No particular reason, I've seen this on an installation procedure.

**philou31** · 24-07-2024, 21:27

A big bug on the forum...

I try to answer you with text instead of pictures...

Content of host_cache table:

Code:

IP                     HOST                     HOST_VALIDATED
192.168.1.150      fr-srvweb           YES
192.168.1.160      fr-srvmail           YES
192.168.1.180      fr-srvmonitor      YES
192.168.1.170      fr-srvcomm        YES
192.168.1.140      fr-srvbackups     YES
192.168.1.190      fr-srvtest            YES

==> All my servers

- Zabbix server+frontend IP address+netmask and OS hostname

Code:

eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether b8:27:eb:75:85:ad brd ff:ff:ff:ff:ff:ff
inet 192.168.1.180/24 brd 192.168.1.255 scope global dynamic noprefixroute eth0
valid_lft 21905sec preferred_lft 21905sec

Hostname: fr-srvmonitor

- Zabbix frontend configurations (like sudo grep \$DB /etc/zabbix/web/zabbix.conf.php)

Code:

$DB['TYPE'] = 'MYSQL';
$DB['SERVER'] = 'DBSERV';
$DB['PORT'] = '3307';
$DB['DATABASE'] = 'zabbix';
$DB['USER'] = 'zabbix';
$DB['PASSWORD'] = 'ABCDEF';
$DB['SCHEMA'] = '';
$DB['ENCRYPTION'] = false;
$DB['KEY_FILE'] = '';
$DB['CERT_FILE'] = '';
$DB['CA_FILE'] = '';
$DB['VERIFY_HOST'] = false;
$DB['CIPHER_LIST'] = '';
$DB['VAULT'] = '';
$DB['VAULT_URL'] = '';
$DB['VAULT_PREFIX'] = '';
$DB['VAULT_DB_PATH'] = '';
$DB['VAULT_TOKEN'] = '';
$DB['VAULT_CERT_FILE'] = '';
$DB['VAULT_KEY_FILE'] = '';
// $DB['VAULT_CACHE'] = true;

- MariaDB server IP address+netmask and DNS resolver address(es)

Code:

IP : 192.168.1.166
Netmask : 255.255.255.0
Gateway : 192.168.1.254
DNS : 192.168.1.5

- select * from mysql.db where user="zabbix"\G (assuming your Zabbix database username is "zabbix")

Code:

Result:
- Host: %
- Db: zabbix
- User: zabbix

- /etc/hosts on the MariaDB server

Code:

127.0.0.1 localhost
::1 localhost
127.0.0.1 fr-nassyno
::1 fr-nassyno

192.168.1.160 fr-srvmail srvmail
192.168.1.170 fr-srvcomm srvcomm
192.168.1.166 fr-nassyno DBSERV
192.168.1.167 fr-nassyno-nfs
192.168.1.190 fr-srvtest srvtest
192.168.1.180 fr-srvmonitor srvmonitor
192.168.1.150 fr-srvweb srvweb
192.168.1.81 ubu-phil phil-games
192.168.1.120 fr-srvansible srvansible
192.168.1.140 fr-srvbackups srvbackups
192.168.1.5 fr-srvDNS srvDNS

- Reverse DNS resolution results for Zabbix server+frontend IP addresses using the DNS resolver(s)

Code:

ash-4.4# nslookup 192.168.1.180
180.1.168.192.in-addr.arpa name = fr-srvmonitor.

Code:

ash-4.4# nslookup fr-srvmonitor
Server: 192.168.1.5
Address: 192.168.1.5#53

Name: fr-srvmonitor.maison
Address: 192.168.1.180

- Information about how the DNS server/resolver is configured to know the IP+hostname mappings about the servers
Using bind.
With 1 zone named "maison" with all servers & IP on it:

Code:

$TTL 10800
$ORIGIN maison.
@ IN SOA fr-srvDNS.maison. root.maison. (
20180906;
3h;
1h;
1w;
1h);
@ IN NS fr-srvDNS.maison.
host IN A 192.168.1.1
fr-srvDNS IN A 192.168.1.5
fr-srvtest IN A 192.168.1.190
fr-srvmail IN A 192.168.1.160
fr-srvcomm IN A 192.168.1.170
fr-srvmonitor IN A 192.168.1.180
fr-srvbackups IN A 192.168.1.140
fr-srvweb IN A 192.168.1.150
fr-nassyno IN A 192.168.1.166
fr-nassyno-nfs IN A 192.168.1.167

And another zone for reverse:

Code:

$TTL 10800
$ORIGIN 1.168.192.in-addr.arpa.
@ IN SOA fr-srvDNS.maison. root.maison. (
20180906;
3h;
1h;
1w;
1h);
@ IN NS fr-srvDNS.maison.
1 IN PTR host.maison.
5 IN PTR fr-srvDNS.
190 IN PTR fr-srvtest.
160 IN PTR fr-srvmail.
170 IN PTR fr-srvcomm.
180 IN PTR fr-srvmonitor.
140 IN PTR fr-srvbackups.
150 IN PTR fr-srvweb.
166 IN PTR fr-nassyno.
167 IN PTR fr-nassyno-nfs.

**philou31** · 24-07-2024, 21:34

Here is the error message after modifying user "zabbix"@"%" to "zabbix"@"fr-srvmonitor" (action on zabbix interface is just to modify DNS name on the server):

Code:

Error in query [UPDATE hosts SET host='fr-srvtest',name='fr-srvtest',monitored_by='0',status='1',tls_connect='1',tls_accept='1',tls_psk_identity='',tls_psk='',tls_issuer='',tls_subject='',proxyid=NULL,proxy_groupid=NULL WHERE hostid='10527'] [The user specified as a definer ('zabbix'@'fr-srvsurv') does not exist] [zabbix.php:17 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → CControllerHostUpdate->doAction() → CApiWrapper->__call() → CFrontendApiWrapper->callMethod() → CApiWrapper->callMethod() → CFrontendApiWrapper->callClientMethod() → CLocalApiClient->callMethod() → CHost->update() → CHost->updateForce() → CHost->massUpdate() → DB::update() → DBexecute() → trigger_error() in include/db.inc.php:362]
L'exécution de l'instruction SQL a échoué"UPDATE hosts SET host='fr-srvtest',name='fr-srvtest',monitored_by='0',status='1',tls_connect='1',tls_accept='1',tls_psk_identity='',tls_psk='',tls_issuer='',tls_subject='',proxyid=NULL,proxy_groupid=NULL WHERE hostid='10527'".

Hostname "fr-srvsurv" was the old name of zabbix server, before become "fr-srvmonitor".

**Markku** · 24-07-2024, 21:46

(Written before seeing your previous post)

Thanks for the information. The DNS configuration is a bit atypical (reverse zone returns non-FQDN records, and NAS has /etc/hosts for the relevant IPs), but apparently MariaDB is still happy with the resolutions, based on the host_cache table.

Now, is it still so that if you configure the Zabbix database permissions for "zabbix"@"fr-srvmonitor" (and drop all other "zabbix" permissions), flush privileges just to be sure, MariaDB rejects connections from Zabbix server? And also, if you configure permissions for "zabbix"@"192.168.1.180", the same thing? What host the host_cache table say at the same time? ("flush hosts" maybe useful before)

Markku

**philou31** · 24-07-2024, 21:54

First test:
only "zabbix"@"fr-srvmonitor", flush privileges, flush hosts ==> host_cache: 192.168.1.180 fr-srvmonitor YES

Second test:
only "zabbix"@"192.168.1.180", flush privileges, flush hosts ==> host_cache: 192.168.1.180 fr-srvmonitor YES

Rejected connections for both.

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Strange issue

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