cc_growpart: respect /etc/growroot-disabled

cloud-initramfs-growroot is an initramfs module in cloud-initramfs-tools
that resizes the root partition before the root is pivoted over.

growroot was used in Ubuntu up to and including 12.10.  The file
/etc/growroot-disabled on the root filesystem was the only way of
disabling the growing of the root partition.

In cloud-init 0.7.2 cloud-init began resizing the root partition
as growpart gained the ability to utilize 'ptupdate' in kernels > 3.8.
This was a big improvement as now the user could disable or enable
the growing of the root partition via user-data.

In order to let users disable growing of / very simplistically cloud-init
will now respect the presense of /etc/growroot-disabled unless config
specifically tells it to ignore that file.

LP: #1234331

1 files changed, 7 insertions, 0 deletions

diff --git a/cloudinit/config/cc_growpart.py b/cloudinit/config/cc_growpart.py
index 2d54aabf..0dd92a46 100644
--- a/cloudinit/config/cc_growpart.py
+++ b/cloudinit/config/cc_growpart.py
@@ -32,6 +32,7 @@ frequency = PER_ALWAYS
 DEFAULT_CONFIG = {
     'mode': 'auto',
     'devices': ['/'],
+    'ignore_growroot_disabled': False,
 }
 
 
@@ -251,6 +252,12 @@ def handle(_name, cfg, _cloud, log, _args):
         log.debug("growpart disabled: mode=%s" % mode)
         return
 
+    if util.is_false(mycfg.get('ignore_growroot_disabled', False)):
+        if os.path.isfile("/etc/growroot-disabled"):
+            log.debug("growpart disabled: /etc/growroot-disabled exists")
+            log.debug("use ignore_growroot_disabled to ignore")
+            return
+
     devices = util.get_cfg_option_list(cfg, "devices", ["/"])
     if not len(devices):
         log.debug("growpart: empty device list")