cloudinit-userdata doesn't handle lists in runcmd properly

[Heather Lanigan]

Doesn't work:
$ cat cloudinit-userdata.yaml
cloudinit-userdata: |
  write_files:
  - content: |
        net.ipv4.conf.all.rp_filter=2
        net.ipv4.conf.default.rp_filter=2
    path: /etc/sysctl.d/99-rp_filter.conf
  postruncmd:
  - [ "sysctl", "-p", "/etc/sysctl.d/99-rp_filter.conf" ]

Replacing the last line does work:
 - sysctl -p /etc/sysctl.d/99-rp_filter.conf

We're forcing pre and post runcmds to be strings. Per the cloudinit docs
(http://cloudinit.readthedocs.io/en/latest/topics/examples.html#run-commands-on-first-boot)
they can also be a list of strings.

[Felipe Reyes (freyes)]

I'm running juju 2.9.34 and jujud is crashing because this reason:

022-08-29 18:43:02 DEBUG juju.cloudconfig.cloudinit network_ubuntu.go:147 generating netplan from network.InterfaceInfos{network.InterfaceInfo{DeviceIndex:0, MACAddress:"00:16:3e:7a:f2:c3", ProviderId:"",
 ProviderSubnetId:"", ProviderNetworkId:"", ProviderSpaceId:"", ProviderVLANId:"", ProviderAddressId:"", AvailabilityZones:[]string(nil), VLANTag:0, InterfaceName:"eth0", ParentInterfaceName:"br11", Interf
aceType:"", Disabled:false, NoAutoStart:false, ConfigType:"dhcp", Addresses:network.ProviderAddresses(nil), ShadowAddresses:network.ProviderAddresses(nil), DNSServers:network.ProviderAddresses(nil), MTU:0,
 DNSSearchDomains:[]string(nil), GatewayAddress:, Routes:[]network.Route(nil), IsDefaultGateway:false, VirtualPortType:"", Origin:"provider"}, network.InterfaceInfo{DeviceIndex:0, MACAddress:"00:16:3e:97:e
b:16", ProviderId:"", ProviderSubnetId:"", ProviderNetworkId:"", ProviderSpaceId:"", ProviderVLANId:"", ProviderAddressId:"", AvailabilityZones:[]string(nil), VLANTag:0, InterfaceName:"eth1", ParentInterfa
ceName:"br11", InterfaceType:"", Disabled:false, NoAutoStart:false, ConfigType:"dhcp", Addresses:network.ProviderAddresses(nil), ShadowAddresses:network.ProviderAddresses(nil), DNSServers:network.ProviderA
ddresses(nil), MTU:0, DNSSearchDomains:[]string(nil), GatewayAddress:, Routes:[]network.Route(nil), IsDefaultGateway:false, VirtualPortType:"", Origin:"provider"}}
2022-08-29 18:43:02 DEBUG juju.service discovery.go:67 discovered init system "systemd" from series "focal"
panic: interface conversion: interface {} is []interface {}, not string

goroutine 5734 [running]:
github.com/juju/juju/cloudconfig.(*unixConfigure).ConfigureJuju(0xc000a9f4d0)
        /build/snapcraft-juju-89be21f465fb3a03c6faac0678176741/parts/juju/build/cloudconfig/userdatacfg_unix.go:260 +0x16a7
github.com/juju/juju/cloudconfig.(*unixConfigure).Configure(0xc000eb2300?)
        /build/snapcraft-juju-89be21f465fb3a03c6faac0678176741/parts/juju/build/cloudconfig/userdatacfg_unix.go:130 +0x2f
github.com/juju/juju/cloudconfig/providerinit.configureCloudinit(0xc000eb2300, {0x622b1c8?, 0xc0019f2c60?})
        /build/snapcraft-juju-89be21f465fb3a03c6faac0678176741/parts/juju/build/cloudconfig/providerinit/providerinit.go:38 +0xb7
github.com/juju/juju/cloudconfig/providerinit.ComposeUserData(0xc000eb2300, {0x622b1c8?, 0xc0019f2c60?}, {0x61a7f00, 0x91251f8})
        /build/snapcraft-juju-89be21f465fb3a03c6faac0678176741/parts/juju/build/cloudconfig/providerinit/providerinit.go:60 +0x8f
github.com/juju/juju/provider/lxd.(*environ).getContainerSpec(_, {_, {_, _}}, {_, _}, {{0xc002bad890, 0x24}, {0x0, 0x0, ...}, ...})
        /build/snapcraft-juju-89be21f465fb3a03c6faac0678176741/parts/juju/build/provider/lxd/environ_broker.go:219 +0x4f1
github.com/juju/juju/provider/lxd.(*environ).newContainer(_, {_, _}, {{0xc002bad890, 0x24}, {0x0, 0x0, 0x0, 0x0, 0x0, ...}, ...}, ...)
        /build/snapcraft-juju-89be21f465fb3a03c6faac0678176741/parts/juju/build/provider/lxd/environ_broker.go:121 +0x35e
github.com/juju/juju/provider/lxd.(*environ).StartInstance(_, {_, _}, {{0xc002bad890, 0x24}, {0x0, 0x0, 0x0, 0x0, 0x0, ...

[Ian Booth (wallyworld)]

Changing to critical due to the panic

[Ben Hoyt (benhoyt)]

Fixing this in https://github.com/juju/juju/pull/14535