While debugging a problem with EDNS records, I wanted to get some cache
info from the PowerDNS
rec_control dump-cache should
supply it, but I did not see it.
# rec_control dump-cache out.txt Error opening dump file for writing: Permission denied
Doh, it’s running as the
pdns user. Let’s write in
# rec_control dump-cache /tmp/out.txt dumped 42053 records # less /tmp/out.txt /tmp/out.txt: No such file or directory
Wait what? No files?
Turns out Systemd has mapped
/tmp into a private location:
# ls -l /tmp/systemd-private-81..34-pdns-recursor.service-1..Q/tmp/out.txt -rw-r----- 1 pdns pdns 2303585 nov 15 15:36 /tmp/systemd-private-81..34-pdns-recursor.service-1..Q/tmp/out.txt
If you know it, it won’t come as a surprise.
# grep -i tmp /lib/systemd/system/pdns-recursor.service PrivateTmp=true