shell-things/etc/chrony/README.md
2023-02-21 17:54:39 +02:00

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# Chrony config files
For some reason Debian package for Chrony doesn't include other config files
so that has to be done by hand like
```
confdir /etc/chrony/chrony.d
```
## Windows
Refer to ../../Windows/time/README.md
## Other random notes
On pools, the default maxsources is 4 and pools would be resolved until
there would be 4 names while the documentation for Telia and Snopyta says
they have only 3. Cloudflare again resolves to two per IP version, so I
assume that means 2.
## Commands of interest:
### Chrony itself
Note: -N uses names specified in config instead of reverse name lookupping
then.
- `chrony -N activity` - what sources are doing
- `chrony -N authdata` - can show that server uses NTS
- `chrony -N ntpdata` - a lot of data on the servers
- `chronyc offline` - offline mode
- `chronyc online` - reconnects servers
- `chrony -N sources` - used timeservers and their statuses
- `chrony -N tracking` - local status (stratum and own clock etc.)
### nmap
Checking that something is an NTP server? Needs root:
```
nmap -sU -p 123 --script=ntp-info 192.168.0.1
```
Checking that something has NTS?
```
nmap -p 4460 -Pn ntp.example.net
```
In [GitHub user jauderho's curated NTS list](https://gist.github.com/jauderho/2ad0d441760fc5ed69d8d4e2d6b35f8d)
user [cadusilva suggests this command instead](https://gist.github.com/jauderho/2ad0d441760fc5ed69d8d4e2d6b35f8d?permalink_comment_id=4192632#gistcomment-4192632):
```'
chronyd -Q -t 3 'server NTP_SERVER_HERE iburst nts maxsamples 1'
```
### Firewall configuration
In case local clients or peers are wanted,
```
ufw allow from 192.168.0.0/16 to any port 123 proto udp
ufw allow from fe80::/10 to any port 123 proto udp
```
A bit wide `192.168.x.x`, but so is `conf.d/local-servers,conf` and
`fe80://10` isn't ULA either.