So, I was in an interview today, and a question was asked about making the DNS entries persistent even if Network Manager overwrites the resolv.conf file.

I replied you could always make the file immutable after your changes. (Please don't lecture about that NOT being the right way to do it, I'm fully aware...just pointing out possibilities during a discussion.) The engineer who was interviewing me told me that no longer works, as Network Manager can now overwrite them anyway. He was quite adamant about it.

I don't see anywhere where anything has changed about immutable files. I asked if they had a script that checks and reverts it to mutable, and he said no, RH/CentOS does that now.

Is there some flag that NM can be configured to ignore immutable files that I've missed? (FTR, it's been a while since I did any sysadmin work...so I just wanted to make sure I missed something here.)

TIA

if you want the job you shouldn't start by criticizing the engineer who interviews you.
while he might be technically wrong (idk), i would agree that what you proposed is an inelegant cludge.
i don't use network-manager if i can avoid it, but generally speaking we are talking about dns resolving which is usually done by another utility.
i use systemd nowadays, and i edit /etc/systemd/resolved.conf.

I didn't criticize the engineer interviewing me at all.

The question was simply how could you do it, and I replied there were several ways (this was specifically in regards to a RHEL/Cent system.) I offered the NetworkManager.conf file first, but he asked what I meant by other ways it could be done, and I rattled off a few. He just was very curt and said that didn't work. He may have been referring to the location having moved in systemd, but he just became very standoffish at that point. I was a little taken aback. Just wondering if there was any more to it than that. (Also, yeah...my first task would be killing NM...)

Hi,

I have just tested on a CentOS 7 machine.
NetworkManager is unable to modified /etc/resolv.conf after it had been set to immutable.

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^ very well, bu we're talking about /etc/resolv.conf, and not /etc/hosts as you originally wrote.

sounds like he suddenly realized that his knowledge is not superior to yours in that area?

to come back to the actual question: i don't know either.
resolv.conf might be rewritten by various applications, depending on your setup.
there's even a resolvconf.conf file, duh.
i did the 'chattr +i' cludge some years ago and it worked.
but since i use only systemd to connect to the network, my previously described method is sufficient.
aside: my router can also do dns, so i could point the appropriate config file to an internal ip.

No worries...I was just wondering if I had missed an update. I'd be willing to bet that, yeah, they have a script/bypass/solution to prevent it built into their config files (which is probably a smart play, frankly...). Appreciate the response.

J

Sorry, my mistake.
I indeed worked on /etc/resolv.conf.
I will update my post above.