[Bug 1706990] Re: With samba installed on Kubuntu 17.04, nmbd.service causes a 10 second boot time regression

[Andreas Hasenack]

Ok, I did some testing. I setup a zesty vm, installed samba (smbd and
nmbd) on it, then configured it to not bring up the network at boot time
(/etc/network/interfaces <- remove "auto eth0"). I can then login at the
console and bring eth0 up or down with "ifup" and "ifdown" commands at
will.

Here is what I observed:

- the boot never hangs
- systemd will give up on the nmbd job after 1min30s. Note that this wait happens in the background and doesn't block other jobs (unless they depend on nmbd, which isn't the case). If I login at the console (still no network) and run "systemd-analyze blame" before that timeout, it will say the system is still booting.
- nmbd actually starts as usual, detects there is no network, and wait for the network *forever*: there is no timeout. Its loop is essentially this:
    while (iface_count_v4_nl() == 0) {
        sleep(5);
        load_interfaces();
    }
- that's when it logs the message "No local IPv4 non-loopback interfaces available, waiting for interface...". It really waits forever.
- in that loop you will notice that it performs a check every 5s. That's why you see the "10s extra delay" every time with such precision: you probably logged between 5-10s after nmbd was started.
- if I run systemd-analyze blame after the 1min30s timeout, i.e., after systemd is "happy" that the system booted because it gave up on the nmbd job, then it will output nmbd.service at the very top with 1m30s, as expected.

To summarize, I believe what's happening is correct and normal for a
machine which only connects to the network after the user logs in. It's
not blocking your boot, nor delaying your login for an extra 10s: that
wait happens in the background, in parallel with all the rest that's
running. And as soon as the network is available, nmbd will detect that
in one if its 5s interval checks, and exit the loop and do its job.

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Title:
  With samba installed on Kubuntu 17.04, nmbd.service causes a 10 second
  boot time regression

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