If you’re getting many “unstrusted issuer” alerts in your app logs, it might be due to some CA trusted certificates outdated.
To fix that, just perform an update:

For Ubuntu/Debian

update-ca-certificates

For CentOS/RedHat

update-ca-trust extract

If you need to push multiple lines to one file through a bash script, you can simply use that syntax:

cat > /etc/ntp.conf << _NTPconf_
  server 1.2.3.4
  server 5.6.7.8
_NTPconf_

Tip: Be aware that if you’re using indentation, last line should not be indented (this would lead you to some errors).

If you want to add line instead of overwriting file (like we did in the previous example), just replace the “>” with “>>” after cat command.

cat >> /etc/ntp.conf << _NTPconf_
  server 1.2.3.4
  server 5.6.7.8
_NTPconf_