Dnsmasq unable to access log file

Question

I'm very new to Linux, Ubuntu and this forum. I am using Ubuntu 20.04 in a VM as a wireless access point and I'm having a problem which is best explained with code:

john@HomeDT:~$ sudo service dnsmasq stop
[sudo] password for john: 
john@HomeDT:~$ sudo service dnsmasq start
Job for dnsmasq.service failed because the control process exited with error code.
See "systemctl status dnsmasq.service" and "journalctl -xe" for details.
john@HomeDT:~$ sudo systemctl status -l dnsmasq
● dnsmasq.service - dnsmasq - A lightweight DHCP and caching DNS server
     Loaded: loaded (/lib/systemd/system/dnsmasq.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Sat 2021-01-30 22:00:31 GMT; 9s ago
    Process: 7541 ExecStartPre=/usr/sbin/dnsmasq --test (code=exited, status=0/SUCCESS)
    Process: 7542 ExecStart=/etc/init.d/dnsmasq systemd-exec (code=exited, status=3)

Jan 30 22:00:30 HomeDT systemd[1]: Starting dnsmasq - A lightweight DHCP and caching DNS server...
Jan 30 22:00:30 HomeDT dnsmasq[7541]: dnsmasq: syntax check OK.
Jan 30 22:00:31 HomeDT dnsmasq[7542]: dnsmasq: cannot open log /tmp/dnsmasq.log: Permission denied
Jan 30 22:00:31 HomeDT dnsmasq[7542]: cannot open log /tmp/dnsmasq.log: Permission denied
Jan 30 22:00:31 HomeDT dnsmasq[7542]: FAILED to start up
Jan 30 22:00:31 HomeDT systemd[1]: dnsmasq.service: Control process exited, code=exited, status=3/NOTIMPLEMENTED
Jan 30 22:00:31 HomeDT systemd[1]: dnsmasq.service: Failed with result 'exit-code'.
Jan 30 22:00:31 HomeDT systemd[1]: Failed to start dnsmasq - A lightweight DHCP and caching DNS server.
john@HomeDT:~$ sudo mv /tmp/dnsmasq.log /tmp.dnsmasq.log.old
john@HomeDT:~$ sudo service dnsmasq start
john@HomeDT:~$ sudo service dnsmasq status
● dnsmasq.service - dnsmasq - A lightweight DHCP and caching DNS server
     Loaded: loaded (/lib/systemd/system/dnsmasq.service; enabled; vendor preset: enabled)
     Active: active (running) since Sat 2021-01-30 22:01:02 GMT; 13s ago
    Process: 7776 ExecStartPre=/usr/sbin/dnsmasq --test (code=exited, status=0/SUCCESS)
    Process: 7777 ExecStart=/etc/init.d/dnsmasq systemd-exec (code=exited, status=0/SUCCESS)
    Process: 7788 ExecStartPost=/etc/init.d/dnsmasq systemd-start-resolvconf (code=exited, status=0/SUCCESS)
   Main PID: 7787 (dnsmasq)
      Tasks: 1 (limit: 4653)
     Memory: 87.7M
     CGroup: /system.slice/dnsmasq.service
             └─7787 /usr/sbin/dnsmasq -x /run/dnsmasq/dnsmasq.pid -u dnsmasq -r /run/dnsmasq/resolv.conf -7 /etc/dnsmasq.d,.dpkg-dist,.dpkg-old,.dpkg-new ->

Jan 30 22:01:00 HomeDT systemd[1]: Starting dnsmasq - A lightweight DHCP and caching DNS server...
Jan 30 22:01:00 HomeDT dnsmasq[7776]: dnsmasq: syntax check OK.
Jan 30 22:01:02 HomeDT systemd[1]: Started dnsmasq - A lightweight DHCP and caching DNS server.

This file that dnsmasq can't access is created by the dnsmasq service and has these permissions:1

I've googled every search term that I can think of for this and I can't find anything that relates. I have tried running various commands that I have found on askubuntu that alter the permissions for the file (sorry, I can't remember what they are) and nothing that I do seems to help.

Does anyone know what I need to do to fix this please?

Thanks in advance

Answer 1

I know this answer comes late, but I found the solution. Just remove the log file and restart dnsmasq

rm /tmp/dnsmasq.log
systemctl restart dnsmasq

A new log file will be generated

EDIT: The fix above is only temporary; next time dnsmasq starts it will fail again. To fix this I uninstalled it with apt and compiled it from source instead

apt remove dnsmasq
cd ~/Downloads
git clone git://thekelleys.org.uk/dnsmasq.git
cd dnsmasq
make install (as root)