Another day another foo, this time done to the check_disk plugin for Nagios on Ubuntu. After updating to 15.10 my disk space check all of a sudden failed with this one here:
DISK CRITICAL - /sys/kernel/debug/tracing is not accessible: Permission denied
It seemed a little odd, especially when I could access that file normally before. So something has changed and the workaround is actually fairly easy. As root edit the file /etc/nagios-plugins/config/disk.cfg and change the command for check_all_disks. You need to add -A -i ‘/sys’ to the command line. So your command for check_all_disks will look like this:
# 'check_all_disks' command definition
command_line /usr/lib/nagios/plugins/check_disk -w '$ARG1$' -c '$ARG2$' -e -A -i '/sys'
Restart Nagios and all is good. After I fixed it this way I found, that it is actually filed as a bug 1516451 in Ubuntu’s Launchpad here