Block youtube.com

[nicholas5421]

Hello All,

I am trying to block access to youtube by adding the static record to hosts file.
But i still have youtube access. It seems like the hosts file have been ignored.

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$ cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
0.0.0.0     youtube.com

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$ ping -c1 youtube.com
PING youtube.com (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.035 ms

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$ dig youtube.com

; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el8 <<>> youtube.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36706
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1452
;; QUESTION SECTION:
;youtube.com.			IN	A

;; ANSWER SECTION:
youtube.com.		257	IN	A	216.58.207.46

;; Query time: 77 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Tue Mar 03 21:19:30 IST 2020
;; MSG SIZE  rcvd: 56

Please help.

[sml]

First, ensure that files comes before anything in your /etc/nsswitch.conf:

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grep ^hosts: /etc/nsswitch.conf

But most probably, it's a DNS caching issue:

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sudo resolvectl flush-caches

DNS lookups may also be cached by another service (dnsmasq, nscd, ...). See How to Flush the DNS Cache on Linux.

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sudo pkill -USR1 dnsmasq

etc.

Try

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grep ^dns= /etc/NetworkManager/NetworkManager.conf

and see if it gives you dns=systemd-resolved or dns=dnsmasq. From Configuring and managing networking:

• dns=dnsmasq or dns=systemd-resolved:
  
  When you use one of these settings, NetworkManager sets either 127.0.0.1 for dnsmasq or 127.0.0.53 as nameserver entry in the /etc/resolv.conf file

[TrevorH]

You'll also find that youtube has multiple URLs so blocking youtube.com like that will not also block www.youtube.com or any other variants on that theme.

[nicholas5421]

Thanks, for your help. It seems to be the solution.

In Centos 8, the newer Firefox adds "www" to youtube.com. So there is no any problem.
Also, we could see that configuration worked in my pings.

I will try to block it with firewalld.
Thanks.

[matt2020]

Also remember the latest Firefox is turning on DoH so will be bypassing all local DNS Settings !

https://support.mozilla.org/en-US/kb/fi ... over-https

You may want to turn that Off.