update-grub-legacy-ec2 fails to detect xen kernel

Bug Description

The update-grub-legacy-ec2 script (which ships with grub-legacy-ec2, which is presumably included under cloud-init umbrella) includes a check to determine whether a kernel is Xen-capable or not. It uses this check in a feature designed to ignore non-Xen kernels on Xen guests, presumably as a safety mechanism. The way in which the check is executed is flawed - it matches against the kernel name. This means that if you are loading a kernel that has an 'unexpected' name, update-grub-legacy-ec2 will ignore the new kernel, regardless of whether or not it is actually Xen-capable. Output looks like this:

Searching for GRUB installation directory ... found: /boot/grub
Searching for default file ... found: /boot/grub/default
Testing for an existing GRUB menu.lst file ... found: /boot/grub/menu.lst
Searching for splash image ... none found, skipping ...
Ignoring non-Xen Kernel on Xen domU host: vmlinuz-3.13.0-36-custom
Found kernel: /boot/vmlinuz-3.13.0-36-generic
Updating /boot/grub/menu.lst ... done

This has been fixed on grub-legacy. Instead of matching the kernel name, it checks the config for CONFIG_XEN=y. In addition, Linux kernels come with CONFIG_XEN=y by default for some time now, and it is perfectly safe to run a Xen-capable kernel on non-Xen hosts.

Steps to reproduce:
1. Compile and generate debs for custom kernel with version string not including '-generic' or '-virtual'
2. Install debs on ec2 system (ami-a94e0c99)
3. Reboot

Expected results:
System comes up with new kernel

Actual results:
System comes up with old kernel, and new kernel is not present in /boot/grub/menu.lst

Impact:
Running ami-a94e0c99, and likely many others, a user can not install a custom kernel without manually editing files. Furthermore, those writes will likely be overwritten by administrative operations in the future.

Recommendation:
Update detection logic to search for CONFIG_XEN=y in the kernel config, and remove version string detection.

Please let me know how I can help this along. I can submit a proposed fix, but am not sure where to send it.

Related bugs:
* bug 1655934: update-grub-legacy-ec2 should detect -aws kernels as appropriate for EC2

fwiw, if you put an executable program 'is_xen_kernel' anywhere in PATH when update-grub-legacy-ec2 is running, it will be used instead of the is_xen_kernel inside.

So, to make this work without any protection is just like:

ln -s /usr/bin/is_xen_kernel /bin/true

Hello evan2645, or anyone else affected,

Accepted cloud-init into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/cloud-init/0.7.9-0ubuntu1~16.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

Hello evan2645, or anyone else affected,

Accepted cloud-init into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/cloud-init/0.7.9-0ubuntu1~16.04.2 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

## launched a xenial instance
$ cat /etc/cloud/build.info
build_name: server
serial: 20170207

## Enable proposed
$ rel=$(lsb_release -sc)
$ line=$(awk '1ドル == "deb" && 2ドル ~ /ubuntu.com/ {
printf("%s %s %s-proposed main universe\n", 1,ドル 2,ドル rel); exit(0) };
' "rel=$rel" /etc/apt/sources.list)
$ echo "$line" | sudo tee /etc/apt/sources.list.d/proposed.list
$ sudo apt-get update -qy
$ sudo apt-get install -qy cloud-init grub-legacy-ec2

## copy -generic to -ec2
$ sudo sh -c 'for i in /boot/*-generic; do n=${i%-generic}-ec2; mv -v $i $n; done'
'/boot/System.map-4.4.0-62-generic' -> '/boot/System.map-4.4.0-62-ec2'
'/boot/abi-4.4.0-62-generic' -> '/boot/abi-4.4.0-62-ec2'
'/boot/config-4.4.0-62-generic' -> '/boot/config-4.4.0-62-ec2'
'/boot/initrd.img-4.4.0-62-generic' -> '/boot/initrd.img-4.4.0-62-ec2'
'/boot/vmlinuz-4.4.0-62-generic' -> '/boot/vmlinuz-4.4.0-62-ec2'

## run update-legacy-grub-ec2
$ sudo update-grub-legacy-ec2

Searching for GRUB installation directory ... found: /boot/grub
Searching for default file ... found: /boot/grub/default
Testing for an existing GRUB menu.lst file ... found: /boot/grub/menu.lst
Searching for splash image ... none found, skipping ...
Found kernel: /boot/vmlinuz-4.4.0-62-generic
Replacing config file /run/grub/menu.lst with new version
Found kernel: /boot/vmlinuz-4.4.0-62-ec2
Replacing config file /run/grub/menu.lst with new version
Updating /boot/grub/menu.lst ... done

Hello evan2645, or anyone else affected,

Accepted cloud-init into yakkety-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/cloud-init/0.7.9-0ubuntu1~16.10.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

## launched a yakkety instance
$ cat /etc/cloud/build.info
build_name: server
serial: 20170207

$ lsb_release -sc
yakkety

## Enable proposed
$ rel=$(lsb_release -sc)
$ line=$(awk '1ドル == "deb" && 2ドル ~ /ubuntu.com/ {
printf("%s %s %s-proposed main universe\n", 1,ドル 2,ドル rel); exit(0) };
' "rel=$rel" /etc/apt/sources.list)
$ echo "$line" | sudo tee /etc/apt/sources.list.d/proposed.list
deb http://nova.clouds.archive.ubuntu.com/ubuntu/ yakkety-proposed main universe

$ sudo apt-get update -qy
$ sudo apt-get install -qy grub-legacy-ec2

$ dpkg-query show grub-legacy-ec2
grub-legacy-ec2 0.7.9-0ubuntu1~16.10.1

## copy -generic to -ec2
$ sudo sh -c 'for i in /boot/*-generic; do n=${i%-generic}-ec2; mv -v $i $n; done'
'/boot/System.map-4.8.0-37-generic' -> '/boot/System.map-4.8.0-37-ec2'
'/boot/abi-4.8.0-37-generic' -> '/boot/abi-4.8.0-37-ec2'
'/boot/config-4.8.0-37-generic' -> '/boot/config-4.8.0-37-ec2'
'/boot/initrd.img-4.8.0-37-generic' -> '/boot/initrd.img-4.8.0-37-ec2'
'/boot/vmlinuz-4.8.0-37-generic' -> '/boot/vmlinuz-4.8.0-37-ec2'

## run update-legacy-grub-ec2
## Note that we see the '-ec2' kernels, before this change they
## wouldn't be considered.
$ sudo update-grub-legacy-ec2
Searching for GRUB installation directory ... found: /boot/grub
Searching for default file ... found: /boot/grub/default
Testing for an existing GRUB menu.lst file ... found: /boot/grub/menu.lst
Searching for splash image ... none found, skipping ...
Found kernel: /boot/vmlinuz-4.8.0-37-generic
Replacing config file /run/grub/menu.lst with new version
Found kernel: /boot/vmlinuz-4.8.0-37-ec2
Replacing config file /run/grub/menu.lst with new version
Updating /boot/grub/menu.lst ... done

Hey all - great to see this getting addressed!

Unfortunately, I'm no longer in a position to test the fix :(. Apologies. Reading through everything though, it seems that it should be effective.

Thanks for all your work!

This bug was fixed in the package cloud-init - 0.7.9-0ubuntu1~16.10.1

---------------
cloud-init (0.7.9-0ubuntu1~16.10.1) yakkety; urgency=medium

* debian/copyright: update License field to include Apache-2.0
* debian/update-grub-legacy-ec2: fix to include kernels whose config
has CONFIG_XEN=y (LP: #1379080).
* debian/update-grub-legacy-ec2: detect kernels ending in -aws as
ec2 bootable (LP: #1655934).
* New upstream release.
- doc: adjust headers in tests documentation for consistency.
- pep8: fix issue found in zesty build with pycodestyle.
- integration test: initial commit of integration test framework
[Wesley Wiedenmeier]
- LICENSE: Allow dual licensing GPL-3 or Apache 2.0 [Jon Grimm]
- Fix config order of precedence, putting kernel command line over system.
[Wesley Wiedenmeier] (LP: #1582323)
- pep8: whitespace fix
- Update the list of valid ssh keys. [Michael Felt]
- network: add ENI unit test for statically rendered routes.
- set_hostname: avoid erroneously appending domain to fqdn
[Lars Kellogg-Stedman] (LP: #1647910)
- doc: change 'nobootwait' to 'nofail' in docs [Anhad Jai Singh]
- Replace an expired bit.ly link in code comment. [Joshua Harlow]

-- Scott Moser <email address hidden> 2017年1月31日 21:02:28 -0500

The verification of the Stable Release Update for cloud-init 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.

This bug was fixed in the package cloud-init - 0.7.9-0ubuntu1~16.04.2

---------------
cloud-init (0.7.9-0ubuntu1~16.04.2) xenial-proposed; urgency=medium

* debian/update-grub-legacy-ec2: fix shell syntax error. (LP: #1662221)

cloud-init (0.7.9-0ubuntu1~16.04.1) xenial-proposed; urgency=medium

* debian/copyright: update License field to include Apache.
* debian/update-grub-legacy-ec2: fix to include kernels whose config
has CONFIG_XEN=y (LP: #1379080).
* debian/patches/azure-use-walinux-agent.patch: continue relying on
walinux agent in stable release.
* New upstream release.
- doc: adjust headers in tests documentation for consistency.
- pep8: fix issue found in zesty build with pycodestyle.
- integration test: initial commit of integration test framework
[Wesley Wiedenmeier]
- LICENSE: Allow dual licensing GPL-3 or Apache 2.0 [Jon Grimm]
- Fix config order of precedence, putting kernel command line over system.
[Wesley Wiedenmeier] (LP: #1582323)
- pep8: whitespace fix [Scott Moser]
- Update the list of valid ssh keys. [Michael Felt]
- network: add ENI unit test for statically rendered routes.
- set_hostname: avoid erroneously appending domain to fqdn
[Lars Kellogg-Stedman] (LP: #1647910)
- doc: change 'nobootwait' to 'nofail' in docs [Anhad Jai Singh]
- Replace an expired bit.ly link in code comment. [Joshua Harlow]
- user-groups: fix bug when groups was provided as string and had spaces
[Scott Moser] (LP: #1354694)
- when adding a user, strip whitespace from group list
[Lars Kellogg-Stedman] (LP: #1354694)
- fix decoding of utf-8 chars in yaml test
- Replace usage of sys_netdev_info with read_sys_net
[Joshua Harlow] (LP: #1625766)
- fix problems found in python2.6 test. [Joshua Harlow]
- Just use file logging by default [Joshua Harlow] (LP: #1643990)
- Improve formatting for ProcessExecutionError [Wesley Wiedenmeier]
- flake8: fix trailing white space
- Doc: various documentation fixes [Sean Bright]
- cloudinit/config/cc_rh_subscription.py: Remove repos before adding
[Brent Baude]
- packages/redhat: fix rpm spec file.
- main: set TZ in environment if not already set. [Ryan Harper]

-- Scott Moser <email address hidden> 2017年2月06日 16:18:28 -0500

Hello evan2645, or anyone else affected,

Accepted cloud-init into trusty-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/cloud-init/0.7.5-0ubuntu1.22 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, and change the tag from verification-needed to verification-done. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed. In either case, details of your testing will help us make a better decision.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

I have verified that cloud-init (0.7.5-0ubuntu1.22) in trusty -proposed does fix the problem.

This bug was fixed in the package cloud-init - 0.7.5-0ubuntu1.22

---------------
cloud-init (0.7.5-0ubuntu1.22) trusty; urgency=medium

* debian/update-grub-legacy-ec2:
- Correctly detect kernels ending in -aws as kernels that can boot on EC2
(LP: #1655934)
- Consider kernels with CONFIG_XEN=y bootable on aws. (LP: #1379080)

-- Scott Moser <email address hidden> 2017年6月08日 19:25:41 -0400