Thanks for reporting this issue.
I could reproduce the issue in fresh lxc containers in focal and in impish, although it is indeed not present in bionic:
apt update apt install -y monitoring-plugins mkdir /reproduce mount -t tmpfs -o rw,size=2G tmpfs /reproduce /usr/lib/nagios/plugins/check_disk -w 10% -c 5% -p /reproduce DISK UNKNOWN - free space:|
Thanks for reporting this issue.
I could reproduce the issue in fresh lxc containers in focal and in impish, although it is indeed not present in bionic:
apt update nagios/ plugins/ check_disk -w 10% -c 5% -p /reproduce
apt install -y monitoring-plugins
mkdir /reproduce
mount -t tmpfs -o rw,size=2G tmpfs /reproduce
/usr/lib/
DISK UNKNOWN - free space:|