Os_defs.cache error

Good day

I have a separate virtual machine for LibreNMS web, that does not poll devices. When I go in Capture Debug Information and click Run, I see next:

LibreNMS Discovery

SQL[select `migration` from `migrations` order by `id` desc limit 1 [] 12.38ms] 
  

SQL[select count(*) as aggregate from `migrations` limit 1 [] 10.34ms] 
  

SQL[SELECT version() [] 12.9ms] 
  

===================================
Version info:
Commit SHA: 172e759720797e4c8f99c5605f323701a9520496
Commit Date: 1592424845
DB Schema: 2020_05_22_020303_alter_metric_column (168)
PHP: 7.3.17
MySQL: 5.5.65-MariaDB
RRDTool: 1.7.1
SNMP: NET-SNMP 5.7.2
==================================DEBUG!

Updating os_def.cache  


Warning: file_put_contents(/opt/librenms/cache/os_defs.cache): failed to open stream: Permission denied in /opt/librenms/LibreNMS/Util/OS.php on line 109

SQL[SELECT * FROM `devices` WHERE disabled = 0 AND snmp_disable = 0 AND `hostname` LIKE '172.21.28.3' AND poller_group IN(-1) ORDER BY device_id DESC [] 10.32ms] 
  

/opt/librenms/discovery.php 172.21.28.3 2020-06-18 14:13:46 - 0 devices discovered in 0.311 secs  

MySQL [1/0.01s]: Cell[1/0.01s] Row[-1/-0.01s] Rows[1/0.01s] Column[0/0.00s] Update[0/0.00s] Insert[0/0.00s] Delete[0/0.00s]

RRD [0/0.00s]:

in CLI like this:

ls -la /opt/librenms/cache/os_defs.cache
ls: cannot access /opt/librenms/cache/os_defs.cache: There is no such file or directory

maybe this is a bug.

It means librenms can’t write to the folder. Fix your permissions. ./validate.php should have info for you.

Nope.
rights to the catalog correct, user and group librenms.
logged into user librenms and successfully created a file in this directory.

./validate.php:

====================================
Component | Version
--------- | -------
LibreNMS  | 1.64.1-159-g172e759
DB Schema | 2020_05_22_020303_alter_metric_column (168)
PHP       | 7.3.17
Python    | 3.6.8
MySQL     | 5.5.65-MariaDB
RRDTool   | 1.7.1
SNMP      | NET-SNMP 5.7.2
====================================

[OK]    Composer Version: 1.10.7
[OK]    Dependencies up-to-date.
[OK]    Database connection successful
[OK]    Database schema correct
[WARN]  Your local git contains modified files, this could prevent automatic updates.
        [FIX]:
        You can fix this with ./scripts/github-remove
        Modified Files:
         LibreNMS/Util/Smokeping.php
         app/Http/Controllers/Widgets/TopDevicesController.php
         includes/definitions/smartax.yaml
         includes/html/api_functions.inc.php
         includes/html/pages/device/showconfig.inc.php
         includes/html/pages/device/vlans.inc.php
         includes/html/print-vlan.inc.php
         misc/config_definitions.json
         resources/lang/en/settings.php
         resources/views/device/tabs/latency.blade.php
         resources/views/layouts/menu.blade.php
[FAIL]  We have found some files that are owned by a different user than librenms, this will stop you updating automatically and / or rrd files being updated causing graphs to fail.
        [FIX]:
        sudo chown -R librenms:librenms /opt/librenms
        sudo setfacl -d -m g::rwx /opt/librenms/rrd /opt/librenms/logs /opt/librenms/bootstrap/cache/ /opt/librenms/storage/
        sudo chmod -R ug=rwX /opt/librenms/rrd /opt/librenms/logs /opt/librenms/bootstrap/cache/ /opt/librenms/storage/
        Files:
         /opt/librenms/rrd/_smokeping/rrd/__sortercache/data.FPing.storable