[Bug 1713747] Update Released

[Brian Murray]

The verification of the Stable Release Update for klibc has completed
successfully and the package has now been released to -updates.
Subsequently, the Ubuntu Stable Release Updates Team is being
unsubscribed and will not receive messages about this bug report.  In
the event that you encounter a regression using the package from
-updates please report a new bug using ubuntu-bug and tag the bug report
regression-update so we can easily find any regressions.

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https://bugs.launchpad.net/bugs/1713747

Title:
  missing DOMAINSEARCH in initramfs output files if the DHCP server
  doesn't provide one

Status in isc-dhcp package in Ubuntu:
  Fix Released
Status in klibc package in Ubuntu:
  Fix Released
Status in isc-dhcp source package in Xenial:
  Triaged
Status in klibc source package in Xenial:
  Fix Released
Status in isc-dhcp source package in Zesty:
  Fix Committed
Status in klibc source package in Zesty:
  Fix Released

Bug description:
  [Impact]
  Systems booted off the network where the DHCP server provides a domain name but no search domains may wish to rely on the domain name as a search value (as is done in isc-dhcp in userland, outside the initramfs), to be able to use short names for resolving hosts.

  [Test cases]
  1) Boot a system with a remote root over the network
   - Typically this requires adding ip=(some IP settings) or ip=dhcp on the kernel command-line, and is better done automatically.
  One good setup for this is to use MaaS to configure the system; where it will require a remote root over iSCSI.
  2) Break boot in the initramfs (adding 'break=bottom' or 'break=premount' to stop in the initramfs at its end, or just before it mounts filesystems)
  3) Validate the contents of /etc/resolv.conf and /run/net-*.conf.

  [Regression potential]
  Potential regressions would include incorrectly resolving names, bad configuration of /etc/resolv.conf (invalid values for the fields, or missing fields), or even failure to mount the remote root in the cases where name resolution is required to find the remote server.

  --

  For networked systems, for instance booting with an iSCSI root,
  dhclient writes an output file in the form of /run/net-<iface>.conf
  that contains data for other programs to consume. This allows, for
  instance, open-iscsi to get the right information and properly connect
  to the server to mount the root filesystem.

  It is common for DHCP servers to only provide a domain name value, and
  no search domains. In this case, isc-dhcp doesn't currently write
  DOMAINSEARCH, but people may wish to use short names to resolve things
  (such as in iSCSI server).

  In the not-initramfs dhclient-script, when domain_search isn't
  provided but domain_name is, domain_name is written to the search
  string. If both are provided, domain_search is written. The initramfs
  enter hook should do the same.

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