CHATTR - DNS Nameserver file (immutable)

Check if immutable attribute is currently applied or not:

lsattr /etc/resolv.conf

Result

----i---------e------- /etc/resolv.conf

Remove it:

sudo chattr -i /etc/resolv.conf

Verify:

lsattr /etc/resolv.conf

Result

--------------e------- /etc/resolv.conf

Make changes to the resolv file for DNS nameservers:

nano /etc/resolv.conf CTRL+X (save) > Y > ENTER

Apply the attribute again:

sudo chattr -+ /etc/resolv.conf

Result

----i---------e------- /etc/resolv.conf

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