[Bug 1931455] Re: open-iscsi fails to create nodes directory

[Christian Ehrhardt ]

Hi,
First of all there are two services - and maybe outlining the difference and the reasoning will help here.

# Reasons

It is fair to say that probably >99% of the users are not using open-
iscsi and therefore having the daemon started on install (and it is
default installed for cases that need it on start to connect to their
data) would mean that millions of system would consume a little bit of
memory and cpu. This is a matter of scale, so it might not matter for me
or you on your system, but on millions of nodes that adds up to power &
space consumption.

# Two Services

There is:
a) ● iscsid.service - iSCSI initiator daemon (iscsid)
     Loaded: loaded (/lib/systemd/system/iscsid.service; disabled; vendor preset: enabled)
     Active: inactive (dead)
TriggeredBy: ● iscsid.socket
       Docs: man:iscsid(8)

This one you can see is socket activated, that means by default it also
isn't started but the iscsiadm command mentioned by Simon will find the
socket, then it is transparently started and will work. Again to have it
off by default, but working right away. That is enough to probe &
configure iscsi - you don't need more than that extra socket provided by
systemd.

b) ● open-iscsi.service - Login to default iSCSI targets
     Loaded: loaded (/lib/systemd/system/open-iscsi.service; enabled; vendor preset: enabled)
     Active: inactive (dead)
  Condition: start condition failed at Mon 2021-06-07 06:44:26 UTC; 3 days ago
       Docs: man:iscsiadm(8)
             man:iscsid(8)

This one is responsible to log into configured targets, and as long as
none are configured there is no reason to start it, hence the
conditions.


I'd be concerned if targets were configured and it would not start, but that isn't the case here.
As presented here I guess it is not a problem, but I'm open for discussion.

If one thinks that this clarification was very helpful let us know,
because then maybe we should make it part of the official docs that
Simon pointed to.

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https://bugs.launchpad.net/bugs/1931455

Title:
  open-iscsi fails to create nodes directory

Status in open-iscsi package in Ubuntu:
  Incomplete

Bug description:
  open-iscsi will not run without the nodes directory, but the nodes
  directory is created and populated by the open-iscsi service.
  Chicken/Egg.

  Mitigated by creating and populating the nodes with junk directories
  to be deleted later:

  linuxsudoer at banana01ubu:/etc/iscsi$ sudo systemctl status open-iscsi.service
  ● open-iscsi.service - Login to default iSCSI targets
       Loaded: loaded (/lib/systemd/system/open-iscsi.service; enabled; vendor preset: enabled)
       Active: inactive (dead)
    Condition: start condition failed at Tue 2021-06-08 19:05:21 UTC; 25min ago
  ---->        ├─ ConditionDirectoryNotEmpty=|/etc/iscsi/nodes was not met
               └─ ConditionDirectoryNotEmpty=|/sys/class/iscsi_session was not met
         Docs: man:iscsiadm(8)
               man:iscsid(8)

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