Crash due to a lack of a root-fs

This bug was originally filed in Launchpad as [LP: #1782575](https://bugs.launchpad.net/cloud-init/+bug/1782575)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2018-07-19T13:41:37.526366+00:00

date_fix_committed = None

date_fix_released = None

id = 1782575

importance = low

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1782575

milestone = None

owner = paelzer

owner_name = Christian Ehrhardt 

private = False

status = triaged

submitter = paelzer

submitter_name = Christian Ehrhardt 

tags = []

duplicates = []

_Launchpad user **Christian Ehrhardt (paelzer)** wrote on 2018-07-19T13:41:37.526366+00:00_

Hey, this certainly isn't the most important case.
But I wanted to report it to make you aware.

For bug 1732028 I was trying different configs.
One was an empty /etc/fstab with the kernel providing the iscsi root.

In that case cloud init runs and since it does not check on RW for / it crashes a bit less soft than it could be.

[ 1304.092816] cloud-init[416]: Traceback (most recent call last):
[ 1305.090202] cloud-init[416]: File "/usr/bin/cloud-init", line 11, in
[ 1305.591502] cloud-init[416]: load_entry_point('cloud-init==18.3', 'console_scripts', 'cloud-init')()
[ 1306.590627] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 882, in main[ OK ] Started ebtables ruleset.

[ 1308.196853] cloud-init[416]: get_uptime=True, func=functor, args=(name, args))
[ 1308.595178] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 2482, in log_time
[ 1309.397478] cloud-init[416]: ret = func(*args, **kwargs)
[ 1309.495795] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 603, in status_wrapper
[ 1309.591048] cloud-init[416]: util.ensure_dirs((data_d, link_d,))
[ 1309.594596] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1540, in ensure_dirs
[ 1309.598989] cloud-init[416]: ensure_dir(d, mode)
[ 1310.792843] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1580, in ensure_dir
[ 1310.800009] cloud-init[416]: os.makedirs(path)
[ 1311.194429] cloud-init[416]: File "/usr/lib/python3.6/os.py", line 210, in makedirs
[ 1311.199855] cloud-init[416]: makedirs(head, mode, exist_ok)
[ 1311.594192] cloud-init[416]: File "/usr/lib/python3.6/os.py", line 220, in makedirs
[ 1311.597483] cloud-init[416]: mkdir(name, mode)
[ 1311.599771] cloud-init[416]: OSError: [Errno 30] Read-only file system: '/var/lib/cloud'
[ 1312.098866] cloud-init[416]: Error in sys.excepthook:
[ 1312.494095] cloud-init[416]: Traceback (most recent call last):
[ 1312.499649] cloud-init[416]: File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 145, in apport_excepthook
[ 1312.895912] cloud-init[416]: os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0o640), 'wb') as f:
[ 1312.990471] cloud-init[416]: OSError: [Errno 30] Read-only file system: '/var/crash/_usr_bin_cloud-init.0.crash'
[ 1312.994822] cloud-init[416]: Original exception was:
[ 1312.998082] cloud-init[416]: Traceback (most recent call last):
[ 1313.389856] cloud-init[416]: File "/usr/bin/cloud-init", line 11, in
[ 1313.795775] cloud-init[416]: load_entry_point('cloud-init==18.3', 'console_scripts', 'cloud-init')()
[ 1314.193905] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 882, in main
[ 1314.199596] cloud-init[416]: get_uptime=True, func=functor, args=(name, args))
[ 1314.997439] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 2482, in log_time
[ 1316.190352] cloud-init[416]: ret = func(*args, **kwargs)
[ 1316.198620] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 603, in status_wrapper
[ 1316.290214] cloud-init[416]: util.ensure_dirs((data_d, link_d,))
[ 1316.295751] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1540, in ensure_dirs
[ 1316.690112] cloud-init[416]: ensure_dir(d, mode)
[ 1316.696509] cloud-init[416]: File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1580, in ensure_dir
[ 1316.893821] cloud-init[416]: os.makedirs(path)
[ 1318.097629] cloud-init[416]: File "/usr/lib/python3.6/os.py", line 210, in makedirs
[ 1318.992338] cloud-init[416]: makedirs(head, mode, exist_ok)
[ 1318.998705] cloud-init[416]: File "/usr/lib/python3.6/os.py", line 220, in makedirs
[ 1320.804643] cloud-init[416]: mkdir(name, mode)
[ 1323.795736] cloud-init[416]: OSError: [Errno 30] Read-only file system: '/var/lib/cloud'
[FAILED] Failed to start Initial cloud-init job (pre-networking).
See 'systemctl status cloud-init-local.service' for details.

OTOH while the stacktrace is a bit much for this case the message in between is sort of clear
  [ 1311.599771] cloud-init[416]: OSError: [Errno 30] Read-only file system: '/var/lib/cloud'

As I said I only wanted to let you know if you want to adapt that to not even try to run in those cases and maybe throw less text at the user.
Feel free to just mark it invalid if you are fine with that being the messaging in this case.