The caching feature adds a new python module, boom.cache to the Boom package. This implements an optional caching facility for boot images (kernels, initramfs, etc.). The cache preserves the content of files such as /boot/vmlinux-$(VERSION) and /boot/initramfs-$(VERSION).img so that boom boot entries that reference these files can still be used following major system upgrades that may purge content from /boot.

The cache is physically located (in the default configuration) at /boot/boom/cache, and consists of image files (named with an SHA1 hash and a .img extension), and a single JSON metadata file, "cacheindex.json":

$ tree boom/cache
boom/cache/
├── 07828df1013c4a5024ecfacae217a74ab5345ea6.img
├── 087beab60378488439a972d1144fef22f2afb1b0.img
├── 1562375e4d022e814ba39521d0852e490b7c07f8.img
├── 3b71f43ff30f4b15b5cd85dd9e95ebc7e84eb5a3.img
├── 3cb9fccc94bb6e40ba08d6be5a471b217fe0d5c7.img
├── 537f67b4c6efe26a873cafc78bea72a6ec32a874.img
├── 537f67b4c6efe26a873cafc78bea72a6ec32a875.img
├── 6c9313159c9d13dbbba3204e39bec870d0ab168d.img
├── a0ce183662af53087fd786e95b43e670c42fe9a2.img
└── cacheindex.json

0 directories, 10 files

The test suite will include validation of the cache internal state and API calls: for QE purposes we should be looking at the operations that users will carry out:

1. Confirm that a cache entry is created automatically when a new boot entry is created
   -> "boom create ..." sets up the entry when automatic caching is enabled (this will be the default)
   -> confirm via tool output ("boom cache list") output should contain matching /vmlinuz-$(VERSION) and /initramfs-$(VERSION).img

2. Confirm that the proper /boot/vmlinuz-$(VERSION) and /boot/initramfs-$(VERSION).img contents are created on a restore operation
   -> "boom cache restore" command, exact details tbd

3. Confirming that the files are restored should be sufficient but if feasible it may also be useful to attempt a boot following an upgrade/restore (I can help with this)

I can provide details of the JSON format if it's useful but it's probably a bit low-level: the main thing to note is that there are three "path" values associated with the entries in the cache. They are referred to in the code (and occasionally tools/docs) as "img_path", "boot_path", and "cache_path":

# img_path  -  The path to an image as specified in a BLS snippet, or an
#              argument to cache_path(), relative to the root of the
#              /boot file system. E.g. "/vmlinuz-5.0.0".
#
# boot_path  - The absolute path to an image relative to the host root
#              file system. E.g. "/boot/vmlinuz-5.0.0".
#
# cache_path - The absolute path to a cached boot image relative to the
#              host root file system. E.g.
#              "/boot/boom/cache/1562375e4d022e814ba39521d0852e490b7c07f8.img"

It shouldn't be necessary to poke into this stuff but some details might help to simplify test cases?

Additional stuff that may be helpful to test (this will be covered by the test suite as well) would be to confirm that images (in both /boot and /boot/boom/cache) are cleaned up when the corresponding boom boot entries are removed. I can add extra details on this if it seems useful.

The Coverity warning is now fixed upstream:

commit d788f82746826d091abcdf76b5f4884c22e3b7de (HEAD -> master, origin/master)
Author: Bryn M. Reeves <bmr>
Date:   Wed May 20 15:14:27 2020 +0100

    boom.cache: use correct variable in load_cache() warning branch
    
    Signed-off-by: Bryn M. Reeves <bmr>

diff --git a/boom/cache.py b/boom/cache.py
index 1dc5e07..cf7de47 100644
--- a/boom/cache.py
+++ b/boom/cache.py
@@ -238,7 +238,7 @@ def load_cache(verify=True, digests=False):
     images = cachedata["images"]
     for image_id in images.keys():
         if image_id not in ids:
-            _log_warn("Found orphan image_id '%s'" % image)
+            _log_warn("Found orphan image_id '%s'" % image_id)
             # clean up?
 
     _log_debug("Loaded %d cache paths and %d images" %

There are four patches now in master that would be good to include in the RHEL8 build:

commit 2b32c40344ff82ba5d7bb959af9b9a97a1a4c142 (HEAD -> master, origin/master)
Author: Bryn M. Reeves <bmr>
Date:   Fri May 22 17:43:49 2020 +0100

    boom.bootloader: decode bytes output of grub2-editenv
    
    Signed-off-by: Bryn M. Reeves <bmr>

commit 50559a4991068a0189e8c5d97c9ed395b3d02bad
Author: Bryn M. Reeves <bmr>
Date:   Fri May 22 17:17:15 2020 +0100

    boom: raise exceptions in load_profiles_for_class() if --debug
    
    Raise exceptions so that the command handler prints the full
    backtrace when --debug is enabled.
    
    Signed-off-by: Bryn M. Reeves <bmr>

commit 235e8e64b7d0c6ba7dcabd899bb7181596e9a137
Author: Bryn M. Reeves <bmr>
Date:   Fri May 22 17:15:15 2020 +0100

    boom.bootloader: raise exceptions in load_entries() if --debug
    
    Raise exceptions so that the command handler prints the full
    backtrace when --debug is enabled.
    
    Signed-off-by: Bryn M. Reeves <bmr>

commit d788f82746826d091abcdf76b5f4884c22e3b7de
Author: Bryn M. Reeves <bmr>
Date:   Wed May 20 15:14:27 2020 +0100

    boom.cache: use correct variable in load_cache() warning branch
    
    Signed-off-by: Bryn M. Reeves <bmr>


Two of these are for supportability: they enable more detailed debugging output in the event that a BootEntry, OsProfile or HostProfile fails to load:

    boom.bootloader: raise exceptions in load_entries() if --debug
    boom: raise exceptions in load_profiles_for_class() if --debug

This means that we can get first-fault debug data from customers directly without needing to provide a debug build or complex instructions.

The other two fix two minor bugs:

    boom.cache: use correct variable in load_cache() warning branch

    Fixes an exception printing a warning message when a specific type of inconsistency is
    detected in the cache metadata. This is not expected to occur other than as a result of
    file system corruption or external modifications of the cacheindex.json file but 
    but the patch improves error reporting & avoids the need for any manual cleanup in the
    event that it did occur.


    boom.bootloader: decode bytes output of grub2-editenv

    Fixes a Unicode decode error affecting Python3 (so only affects RHEL8) that causes an
    error loading "foreign" (i.e. non-boom managed) BLS boot entries. Normally these are
    loaded as read-only (so they can be cloned but not edited): without this patch these
    entries are not loaded since an exception is raised obtaining the value of Grub2
    environment variables used in the entry definition.

    BEFORE:
    # boom list -V
    INFO - Could not load BootEntry '/boot/loader/entries/b49e623f993c4fd7b200c5e350f9cacc-4.18.0-107.el8.x86_64.conf': a bytes-like object is required, not 'str'
    INFO - Could not load BootEntry '/boot/loader/entries/b49e623f993c4fd7b200c5e350f9cacc-0-rescue.conf': a bytes-like object is required, not 'str'
    INFO - Could not load BootEntry '/boot/loader/entries/b49e623f993c4fd7b200c5e350f9cacc-4.18.0-167.el8.x86_64.conf': a bytes-like object is required, not 'str'
    BootID  Version                  Name                     RootDevice     Options                                    MachineID
    b7e8a97 4.18.0-167.el8.x86_64    Red Hat Enterprise Linux /dev/rhel/root root=/dev/rhel/root ro rd.lvm.lv=rhel/root b49e623f9966


    AFTER:
    # boom list -V
    INFO - Marking unknown boot entry as read-only: b49e623f993c4fd7b200c5e350f9cacc-4.18.0-107.el8.x86_64.conf
    INFO - Entry file name does not match boot_id: b49e623f993c4fd7b200c5e350f9cacc-0-rescue.conf
    INFO - Marking unknown boot entry as read-only: b49e623f993c4fd7b200c5e350f9cacc-4.18.0-167.el8.x86_64.conf
    BootID  Version                  Name                     RootDevice            Options                                    MachineID 
    30c3610 4.18.0-107.el8.x86_64    Red Hat Enterprise Linux /dev/mapper/rhel-root $kernelopts $tuned_params                            
    d5479b2 4.18.0-167.el8.x86_64    Red Hat Enterprise Linux /dev/mapper/rhel-root $kernelopts $tuned_params                            
    b7e8a97 4.18.0-167.el8.x86_64    Red Hat Enterprise Linux /dev/rhel/root        root=/dev/rhel/root

    BootEntry 30c3610 and d5479b2 are system-defined BLS entries that are affected by this bug.

Adding the Rebase keyword. This was pm-acked by rhandlin so I guess it is the right thing to do.

The test suite includes unit tests for the newly added functionality - there should be 100% pass with the included suite (~416 tests although the exact number may vary because some tests are skipped if the environment is unsuitable). On my system with current master I see:

  Ran 416 tests in 27.067s

  OK (skipped=4)

And coverage looks like:

$ coverage report
Name                  Stmts   Miss  Cover
-----------------------------------------
boom/__init__.py          5      0   100%
boom/_boom.py           388      9    98%
boom/bootloader.py      942     87    91%
boom/cache.py           358     26    93%
boom/command.py        1348    216    84%
boom/config.py          118     26    78%
boom/hostprofile.py     465     50    89%
boom/legacy.py          167     48    71%
boom/osprofile.py       606     75    88%
boom/report.py          492     56    89%
-----------------------------------------
TOTAL                  4889    593    88%

The cache-specific tests are in tests/cache_tests.py: there are currently 39 unit cases in that module.

Thanks Bryn for the unit test results. Our sanity checks look good as well. Marking this rebase bug verified.

boom-boot-1.2-2.el8    BUILT: Mon Jun 29 08:27:02 CDT 2020

kernel-4.18.0-234.el8    BUILT: Thu Aug 20 12:01:26 CDT 2020
lvm2-2.03.09-5.el8    BUILT: Wed Aug 12 15:51:50 CDT 2020
lvm2-libs-2.03.09-5.el8    BUILT: Wed Aug 12 15:51:50 CDT 2020

SCENARIO - [boom_sanity]
Create a snapshot and perform some boom sanity only checks as this wont be an actual bootable snapshot
Making origin volume
lvcreate --yes -L 300M snapper -n origin
Making snapshot of origin volume
lvcreate --yes -s /dev/snapper/origin -c 128 -n boom_snap -L 100M

Check 0 a. Verify a new profile can be created (this is basically a dup of the above cmd)
boom profile create --from-host --uname-pattern Linux
Check 0 b. Verify a new profile can be created automatically from just current host heuristic
boom profile create --from-host
Check 0 c. Verify a new profile can be created
boom profile create --from-host --uname-pattern el8

Check 1. Verify boom not configured for grub yet warning (Bug 1542952)
Boom already configured for grub. Skipping check.

Generating grub configuration file ...
done

Check 2 a. Verify version numbers not matching an OS profile provide a helpful warning (Bug 1771584#c5)
boom create --title nomatchversion --rootlv snapper/boom_snap --version 2.5.0
Check 2 b. Verify fake OS profiles are properly identified (Bug 1540266)
boom create --profile fake_profile --title title --version 3.10-272.el7 --rootlv snapper/boom_snap
WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'

Check 3. Verify --rootlv and --root-device variations are both accepted (Bug 1543188)
--rootlv: boom create --title 1 --rootlv /dev/snapper/boom_snap
boom list b4d0685
BootID  Version                  Name                     RootDevice            
b4d0685 4.18.0-234.el8.x86_64    Red Hat Enterprise Linux /dev/snapper/boom_snap
boom entry show b4d0685
Boot Entry (boot_id=b4d0685)
  title 1
  machine-id 4329f0e5c0004df9b09a707f827dc31c
  version 4.18.0-234.el8.x86_64
  linux /vmlinuz-4.18.0-234.el8.x86_64
  initrd /initramfs-4.18.0-234.el8.x86_64.img
  options root=/dev/snapper/boom_snap ro rd.lvm.lv=snapper/boom_snap rhgb quiet
  grub_users $grub_users
  grub_arg --unrestricted
  grub_class kernel
boom delete b4d0685

--root-lv: boom create --title 2 --root-lv /dev/snapper/boom_snap
boom list 91a537d
BootID  Version                  Name                     RootDevice            
91a537d 4.18.0-234.el8.x86_64    Red Hat Enterprise Linux /dev/snapper/boom_snap
boom entry show 91a537d
Boot Entry (boot_id=91a537d)
  title 2
  machine-id 4329f0e5c0004df9b09a707f827dc31c
  version 4.18.0-234.el8.x86_64
  linux /vmlinuz-4.18.0-234.el8.x86_64
  initrd /initramfs-4.18.0-234.el8.x86_64.img
  options root=/dev/snapper/boom_snap ro rd.lvm.lv=snapper/boom_snap rhgb quiet
  grub_users $grub_users
  grub_arg --unrestricted
  grub_class kernel
boom delete 91a537d

--rootdevice: boom create --title 3 --rootdevice /dev/snapper/boom_snap
boom list 1c61767
BootID  Version                  Name                     RootDevice            
1c61767 4.18.0-234.el8.x86_64    Red Hat Enterprise Linux /dev/snapper/boom_snap
boom entry show 1c61767
Boot Entry (boot_id=1c61767)
  title 3
  machine-id 4329f0e5c0004df9b09a707f827dc31c
  version 4.18.0-234.el8.x86_64
  linux /vmlinuz-4.18.0-234.el8.x86_64
  initrd /initramfs-4.18.0-234.el8.x86_64.img
  options root=/dev/snapper/boom_snap ro rd.lvm.lv=snapper/boom_snap rhgb quiet
  grub_users $grub_users
  grub_arg --unrestricted
  grub_class kernel
boom delete 1c61767

--root-device: boom create --title 4 --root-device /dev/snapper/boom_snap
boom list 594f8c4
BootID  Version                  Name                     RootDevice            
594f8c4 4.18.0-234.el8.x86_64    Red Hat Enterprise Linux /dev/snapper/boom_snap
boom entry show 594f8c4
Boot Entry (boot_id=594f8c4)
  title 4
  machine-id 4329f0e5c0004df9b09a707f827dc31c
  version 4.18.0-234.el8.x86_64
  linux /vmlinuz-4.18.0-234.el8.x86_64
  initrd /initramfs-4.18.0-234.el8.x86_64.img
  options root=/dev/snapper/boom_snap ro rd.lvm.lv=snapper/boom_snap rhgb quiet
  grub_users $grub_users
  grub_arg --unrestricted
  grub_class kernel
boom delete 594f8c4

Check 4. Verify --root-lv and --root-device verify the lv/device exists (Bug 1543186)
boom create --title no-lv --root-lv snapper/nonlv
WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'
boom create --title no-dev --root-device /dev/sdxyz
WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'
boom create --title 5 --no-dev --root-lv snapper/nonlv
WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'
boom delete 623d07e

Check 5. Verify proper use of user providing --rootlv /dev/* format (Bug 1544914)
boom create --title 6 --rootlv /dev/snapper/boom_snap
WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'
Created entry with boot_id 4c059a8:
  title 6
  machine-id 4329f0e5c0004df9b09a707f827dc31c
  version 4.18.0-234.el8.x86_64
  linux /vmlinuz-4.18.0-234.el8.x86_64
  initrd /initramfs-4.18.0-234.el8.x86_64.img
  options root=/dev/snapper/boom_snap ro rd.lvm.lv=snapper/boom_snap rhgb quiet
  grub_users $grub_users
  grub_arg --unrestricted
  grub_class kernel
boom delete 4c059a8

Check 6. Verify proper rd.lvm.lv entry w/ --root-device option (Also listed in Bug 1544914)
boom create --title 7 --root-device /dev/snapper/boom_snap
WARNING - Boom grub2 integration is disabled in '/boot/../etc/default/boom'
Created entry with boot_id 372913e:
  title 7
  machine-id 4329f0e5c0004df9b09a707f827dc31c
  version 4.18.0-234.el8.x86_64
  linux /vmlinuz-4.18.0-234.el8.x86_64
  initrd /initramfs-4.18.0-234.el8.x86_64.img
  options root=/dev/snapper/boom_snap ro rd.lvm.lv=snapper/boom_snap rhgb quiet
  grub_users $grub_users
  grub_arg --unrestricted
  grub_class kernel
regression check for bug 1840488
boom remove 372913e
boom delete 372913e

Check 7. Verify --grub-arg, grub-class, grub-users, and grub-id specified arguments (r7 rfe 1777364 / r8 rfe 1848123)
Removing volume snapper/boom_snap
Removing origin snapper/origin

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (boom-boot bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:4532