Fixes race conditions like this:
> systemd[1]: Started prometheus-kea-exporter.service.
> kea-exporter[927]: Listening on http://0.0.0.0:9547
> kea-exporter[927]: Socket at /run/kea/dhcp4.sock does not exist. Is Kea running?
> systemd[1]: prometheus-kea-exporter.service: Main process exited, code=exited, status=1/FAILURE
When no devices are given the exporter tries to autodiscover available
disks. The previous DevicePolicy was however preventing the exporter
from accessing any device at all, since only explicitly mentioned ones
were allowed.
This commit adds an allow rule for several device classes that I could
find on my machines, that gets set when no devices are explicitly
configured.
There is an existing problem with nvme devices, that expose a character
device at `/dev/nvme0`, and a (namespaced) block device at
`/dev/nvme0n1`. The character device does not come with permissions that
we could give to the exporter without further impacting the hardening.
crw------- 1 root root 247, 0 27. Jan 03:10 /dev/nvme0
brw-rw---- 1 root disk 259, 0 27. Jan 03:10 /dev/nvme0n1
The autodiscovery only finds the character device, which the exporter
unfortunately does not have access to.
However a simple udev rule can be used to resolve this:
services.udev.extraRules = ''
SUBSYSTEM=="nvme", KERNEL=="nvme[0-9]*", GROUP="disk"
'';
Unfortunately I'm not fully aware of the security implications this
change carries and we should question upstream (systemd) why they did
not include such a rule.
The disk group has no members on any of my machines.
❯ getent group disk
disk❌6:
Otherwise, `postfix_up{path="/var/lib/postfix/queue/public/showq"}` will
always be `0` indicating an postfix outage because this is a unix domain
socket that cannot be connected to:
2021/12/03 14:50:46 Failed to scrape showq socket: dial unix /var/lib/postfix/queue/public/showq: socket: address family not supported by protocol
9fea6d4c85 broke rtl_433-exporter by
introducing several hardening options which do not play well with
rtl_433 requiring writing to USB. More precisely, rtl_433 requires
(a) AF_NETLINK to configure the radio; (b) access to the USB device,
but PrivateDevices=true hides them; (c) rw access to the USB device,
but DeviceAllow= block-lists everything.
This commit was tested on real hardware with a standard NixOS setup.
The timex collector (enabled by default) needs the
adjtimex syscall, which was disabled by
9fea6d4c85.
So allow it unless the timex collector is disabled.
The systemd collector needs AF_UNIX to talk to
/var/run/dbus/system_bus_socket, which was broken
with 9fea6d4c85.
This commit allows AF_UNIX when needed.
In 0.3.0 of the json-exporter[1] it was switched to a different jsonpath
library which made some changes - especially for spaces in keys -
necessary. Also I decided to remove the pretty-printed JSON as this
would interfere with the bash quoting too much. If one needs
pretty-printed output, they can still pipe the output to `jq`.
[1] https://github.com/prometheus-community/json_exporter/releases/tag/v0.3.0
