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Message #27700
[Bug 1806777] Re: cloud-init with iscsi ibft keeps interface at 'manual' so the system gets no dns search domain
This bug was fixed in the package open-iscsi - 2.0.874-5ubuntu2.6
---------------
open-iscsi (2.0.874-5ubuntu2.6) bionic; urgency=medium
* debian/iscsi-disk.rules: Fix bug with LVM on top of iscsi devices.
(LP: #1807978)
open-iscsi (2.0.874-5ubuntu2.5) bionic; urgency=medium
[Scott Moser]
* debian/extra/initramfs.local-top: handle iSCSI iBFT DHCP to correctly
run ipconfig to gather all DHCP config info, including DNS search
domain, which iBFT can't provide. (LP: #1806777)
-- Scott Moser <smoser@xxxxxxxxxx> Tue, 11 Dec 2018 19:14:17 -0500
** Changed in: open-iscsi (Ubuntu Bionic)
Status: Fix Committed => Fix Released
** Changed in: open-iscsi (Ubuntu Cosmic)
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/1806777
Title:
cloud-init with iscsi ibft keeps interface at 'manual' so the system
gets no dns search domain
Status in cloud-init:
Invalid
Status in cloud-init package in Ubuntu:
Invalid
Status in open-iscsi package in Ubuntu:
Fix Released
Status in cloud-init source package in Trusty:
Invalid
Status in open-iscsi source package in Trusty:
Invalid
Status in cloud-init source package in Xenial:
Invalid
Status in open-iscsi source package in Xenial:
Fix Released
Status in cloud-init source package in Bionic:
Invalid
Status in open-iscsi source package in Bionic:
Fix Released
Status in cloud-init source package in Cosmic:
Invalid
Status in open-iscsi source package in Cosmic:
Fix Released
Status in cloud-init source package in Disco:
Invalid
Status in open-iscsi source package in Disco:
Fix Released
Status in open-iscsi package in Debian:
New
Bug description:
[impact]
in bug 1752391, cloud-init was updated to check if the initramfs has
specific iscsi root device config (e.g. static initramfs config, or
ibft), and if so then set up the interface in e/n/i but do not mark it
as 'auto'. This prevents ifupdown from actually running dhclient for
the interface; the reason for the change in that bug was to prevent a
hang at shutdown, as taking down the interface removes access to the
iscsi root disk (thus hanging the system).
However, iBFT has no mechanism in its spec to provide the DNS search
domain, so while the interface ip address/netmask and gateway is
correctly set up when the system finishes booting, it does not contain
any search domain in /etc/resolv.conf. There is no way to get this
information except from an actual dhcp query/response.
In the initramfs, if open-iscsi does not detect ibft (or have static
config built-in) then it will not create a /run/net-IFACE.conf file;
if it does find ibft (or have static config) it will create a /run
/net-IFACE.conf file with the config data that it has (e.g. with ibft,
all the interface configuration that ibft is able and configured to
provide). After this (setting up the interface and mounting the root
dev), ipconfig runs and checks for the existence of /run/net-
IFACE.conf file. If it does NOT exist, then ipconfig creates it
containing the result of the dhcp lease response that ipconfig
received - which includes the dns search domain. However, if there is
already a /run/net-IFACE.conf file, ipconfig does NOT update it. So,
the file created by open-iscsi remains, without any dns search domain.
Once the system boots, resolvconf checks for existance of the /etc
/net-IFACE.conf file, and if found it transfers some of the data into
/etc/resolv.conf (e.g. the dns search domain). Since it does not
contain any dns search domain, the /etc/resolv.conf file does not
contain it either.
If the system is configured to start dhclient for the interface, then
dhclient receives and sets up the system resolv.conf to use the dns
search domain correctly.
For trusty: cloud-init is very different and sets up the running
system ifupdown to start dhclient for the root device interface. The
dns search domain is therefore configured by dhclient in the runtime
system.
For xenial: cloud-init sets up the iscsi root device's interface with
a e/n/i configuration for dhcp, but leaves its 'auto' line commented
out, e.g.:
# control-manual ens3f0
iface ens3f0 inet dhcp
dns-nameservers 169.254.169.254
gateway 10.0.0.1
this results in no dns search domain for the system. (note: as
mentioned above, it does this due to bug 1752391).
For bionic and later: cloud-init sets up netplan instead of ifupdown;
netplan has no such 'auto' mechanism. The initramfs-tools scripts
create a /run/netplan/$DEVICE.yaml file which (when ibft uses dhcp)
contains the 'critical' parameter, causing netplan to create a
systemd-networkd .network file with the "CriticalConnection" parameter
set to true, which prevents systemd-networkd from ever taking the
interface down, which avoids the hang on shutdown (or any other time
dhcp fails/stops for the interface). However, it is still possible to
remove netplan and install ifupdown in bionic (and later), and when
that is done this bug exists, so it should be fixed in those releases
also.
[test case]
start a xenial system that uses ibft and check /etc/resolv.conf; there
will be no dns search domain.
for bionic or later, start a system that uses ibft, then install
ifupdown and resolvconf and remove netplan.io. When the system is
rebooted, the /etc/resolv.conf will not have any dns search domain.
[regression potential]
as this slightly changes when/how open-iscsi creates a
/run/net-$DEVICE.conf file, this has the potential to boot a system
with wrong or even no network configuration, when the system
configures an iscsi device at boot, e.g. with iBFT. However, the
patch does perform a 'fallback' which should prevent such failure when
iBFT does work but ipconfig does not.
[other info]
this appears to have been introduced by bug 1752391. This bug may
possibly also exist if the "ip=" parameter is used, which also
triggers the cloud-init code that sets the runtime interface to
'manual' instead of 'auto', though I have not specifically tested
that.
Trusty's open-iscsi does *not* create a /run/net-$DEVICE.conf file, so
the initramfs there will always run ipconfig to gather dhcp data and
save that; so this bug should not affect trusty.
Bionic and later do not have this problem with netplan, which is their
default, but as noted above if an end-user replaces netplan with
ifupdown, this problem still exists.
Side note: bug 1752391 might not be fixed for bionic and later for
systems with static iBFT (i.e. not DHCP iBFT) becuase the 'critical'
param is only added if DHCP is used (for ipv4 or ipv6).
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References