[Bug 1745531] [NEW] Reinforce hostname preseed regex

[Hua Zhang]

Public bug reported:

This is the same issue reported in https://bugs.launchpad.net/ubuntu/+source/preseed/+bug/1452202
However that is marked as 'Fix Released' and the issue is still occurring so it seems best to just open a new bug according to Eric's comment.

The present hostname preseed regex looks like:

if ! echo "$RET" | grep -q 'ubuntu'; then
   ...
   /bin/sed -i "s/$CURRENT_HOSTNAME/$NETCFG_HOSTNAME/" /etc/hosts
   ...
fi

There are still multiple problems with them according to Peter's comment
(https://bugs.launchpad.net/ubuntu/+source/preseed/+bug/1452202/comments/64)
and Mathieu's comment
(https://bugs.launchpad.net/ubuntu/+source/preseed/+bug/1452202/comments/93).

- The default hostname is 'ubuntu', and is the value you will get if
nothing is preseeded -- we *do* need to skip it in this case, although
the grep may need to be more precise. A name like 'ubuntuxenial' should
match this grep.

- The sed needs to be fixed to more appropriately catch for the exact
string, rather than any substring -- ie. it should not match
'ipv6-allnodes' if the name received from DHCP was 'node'. It should
only match and replace for 'node'.

So the fix will try to:

1) Keep the if statement and add the -w option to grep to be more robust
2) Modify the sed cmd with word boundaries (\b) to be more robust as well.

** Affects: preseed (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: sts

** Tags added: sts

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https://bugs.launchpad.net/bugs/1745531

Title:
  Reinforce hostname preseed regex

Status in preseed package in Ubuntu:
  New

Bug description:
  This is the same issue reported in https://bugs.launchpad.net/ubuntu/+source/preseed/+bug/1452202
  However that is marked as 'Fix Released' and the issue is still occurring so it seems best to just open a new bug according to Eric's comment.

  The present hostname preseed regex looks like:

  if ! echo "$RET" | grep -q 'ubuntu'; then
     ...
     /bin/sed -i "s/$CURRENT_HOSTNAME/$NETCFG_HOSTNAME/" /etc/hosts
     ...
  fi

  There are still multiple problems with them according to Peter's
  comment
  (https://bugs.launchpad.net/ubuntu/+source/preseed/+bug/1452202/comments/64)
  and Mathieu's comment
  (https://bugs.launchpad.net/ubuntu/+source/preseed/+bug/1452202/comments/93).

  - The default hostname is 'ubuntu', and is the value you will get if
  nothing is preseeded -- we *do* need to skip it in this case, although
  the grep may need to be more precise. A name like 'ubuntuxenial'
  should match this grep.

  - The sed needs to be fixed to more appropriately catch for the exact
  string, rather than any substring -- ie. it should not match
  'ipv6-allnodes' if the name received from DHCP was 'node'. It should
  only match and replace for 'node'.

  So the fix will try to:

  1) Keep the if statement and add the -w option to grep to be more robust
  2) Modify the sed cmd with word boundaries (\b) to be more robust as well.

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