Just sharing a problem I've faced and the workaround for this issue.
I've just upgraded from 22.03.2 to 22.03.3 while preserving all settings. After the upgrade, AdGuardHome stopped responding.
Looking at the logs I've found the error "[fatal] initing hosts container: hosts container: path at index 0: stat etc/hosts: os: DirFS with empty root".
The problem: when upgrading OpenWrt from 22.03.2 to 22.03.3, the new AdGuardHome version (0.107) is updating the configuration file schema of file /etc/adguardhome.yaml from version 12 to version 14.
The schema upgrade is automatic, but the there is a new section in the /etc/adguardhome.yaml file as follows:
(...)
clients:
runtime_sources:
whois: true
arp: true
rdns: true
dhcp: true
hosts: true
persistent: []
(...)
According to this other topic it seems an issue of the AdGuardHome version included in 22.03.3 (0.107) and AdGuardHome 0.108 seems to solve this problem.
Searching the web I've also found this thread: https://github.com/AdguardTeam/AdGuardHome/issues/5264
Since I want to keep my 22.03.3 with all default version packages, the workaround suggested by the above thread worked for me with AdGuardHome 0.107 (included in OpenWrt 22.03.3), which consists in changing hosts: true to hosts: false in the /etc/adguardhome.yaml file as follows:
(...)
clients:
runtime_sources:
whois: true
arp: true
rdns: true
dhcp: true
hosts: false
persistent: []
(...)