incus CLI breaks if HOME is invalid

[stefanor]

Required information

• Distribution: Debian
• Distribution version: trixie (testing)
• The output of "incus info":

incus info output

config:
  images.auto_update_interval: "0"
api_extensions:
- storage_zfs_remove_snapshots
- container_host_shutdown_timeout
- container_stop_priority
- container_syscall_filtering
- auth_pki
- container_last_used_at
- etag
- patch
- usb_devices
- https_allowed_credentials
- image_compression_algorithm
- directory_manipulation
- container_cpu_time
- storage_zfs_use_refquota
- storage_lvm_mount_options
- network
- profile_usedby
- container_push
- container_exec_recording
- certificate_update
- container_exec_signal_handling
- gpu_devices
- container_image_properties
- migration_progress
- id_map
- network_firewall_filtering
- network_routes
- storage
- file_delete
- file_append
- network_dhcp_expiry
- storage_lvm_vg_rename
- storage_lvm_thinpool_rename
- network_vlan
- image_create_aliases
- container_stateless_copy
- container_only_migration
- storage_zfs_clone_copy
- unix_device_rename
- storage_lvm_use_thinpool
- storage_rsync_bwlimit
- network_vxlan_interface
- storage_btrfs_mount_options
- entity_description
- image_force_refresh
- storage_lvm_lv_resizing
- id_map_base
- file_symlinks
- container_push_target
- network_vlan_physical
- storage_images_delete
- container_edit_metadata
- container_snapshot_stateful_migration
- storage_driver_ceph
- storage_ceph_user_name
- resource_limits
- storage_volatile_initial_source
- storage_ceph_force_osd_reuse
- storage_block_filesystem_btrfs
- resources
- kernel_limits
- storage_api_volume_rename
- network_sriov
- console
- restrict_dev_incus
- migration_pre_copy
- infiniband
- dev_incus_events
- proxy
- network_dhcp_gateway
- file_get_symlink
- network_leases
- unix_device_hotplug
- storage_api_local_volume_handling
- operation_description
- clustering
- event_lifecycle
- storage_api_remote_volume_handling
- nvidia_runtime
- container_mount_propagation
- container_backup
- dev_incus_images
- container_local_cross_pool_handling
- proxy_unix
- proxy_udp
- clustering_join
- proxy_tcp_udp_multi_port_handling
- network_state
- proxy_unix_dac_properties
- container_protection_delete
- unix_priv_drop
- pprof_http
- proxy_haproxy_protocol
- network_hwaddr
- proxy_nat
- network_nat_order
- container_full
- backup_compression
- nvidia_runtime_config
- storage_api_volume_snapshots
- storage_unmapped
- projects
- network_vxlan_ttl
- container_incremental_copy
- usb_optional_vendorid
- snapshot_scheduling
- snapshot_schedule_aliases
- container_copy_project
- clustering_server_address
- clustering_image_replication
- container_protection_shift
- snapshot_expiry
- container_backup_override_pool
- snapshot_expiry_creation
- network_leases_location
- resources_cpu_socket
- resources_gpu
- resources_numa
- kernel_features
- id_map_current
- event_location
- storage_api_remote_volume_snapshots
- network_nat_address
- container_nic_routes
- cluster_internal_copy
- seccomp_notify
- lxc_features
- container_nic_ipvlan
- network_vlan_sriov
- storage_cephfs
- container_nic_ipfilter
- resources_v2
- container_exec_user_group_cwd
- container_syscall_intercept
- container_disk_shift
- storage_shifted
- resources_infiniband
- daemon_storage
- instances
- image_types
- resources_disk_sata
- clustering_roles
- images_expiry
- resources_network_firmware
- backup_compression_algorithm
- ceph_data_pool_name
- container_syscall_intercept_mount
- compression_squashfs
- container_raw_mount
- container_nic_routed
- container_syscall_intercept_mount_fuse
- container_disk_ceph
- virtual-machines
- image_profiles
- clustering_architecture
- resources_disk_id
- storage_lvm_stripes
- vm_boot_priority
- unix_hotplug_devices
- api_filtering
- instance_nic_network
- clustering_sizing
- firewall_driver
- projects_limits
- container_syscall_intercept_hugetlbfs
- limits_hugepages
- container_nic_routed_gateway
- projects_restrictions
- custom_volume_snapshot_expiry
- volume_snapshot_scheduling
- trust_ca_certificates
- snapshot_disk_usage
- clustering_edit_roles
- container_nic_routed_host_address
- container_nic_ipvlan_gateway
- resources_usb_pci
- resources_cpu_threads_numa
- resources_cpu_core_die
- api_os
- container_nic_routed_host_table
- container_nic_ipvlan_host_table
- container_nic_ipvlan_mode
- resources_system
- images_push_relay
- network_dns_search
- container_nic_routed_limits
- instance_nic_bridged_vlan
- network_state_bond_bridge
- usedby_consistency
- custom_block_volumes
- clustering_failure_domains
- resources_gpu_mdev
- console_vga_type
- projects_limits_disk
- network_type_macvlan
- network_type_sriov
- container_syscall_intercept_bpf_devices
- network_type_ovn
- projects_networks
- projects_networks_restricted_uplinks
- custom_volume_backup
- backup_override_name
- storage_rsync_compression
- network_type_physical
- network_ovn_external_subnets
- network_ovn_nat
- network_ovn_external_routes_remove
- tpm_device_type
- storage_zfs_clone_copy_rebase
- gpu_mdev
- resources_pci_iommu
- resources_network_usb
- resources_disk_address
- network_physical_ovn_ingress_mode
- network_ovn_dhcp
- network_physical_routes_anycast
- projects_limits_instances
- network_state_vlan
- instance_nic_bridged_port_isolation
- instance_bulk_state_change
- network_gvrp
- instance_pool_move
- gpu_sriov
- pci_device_type
- storage_volume_state
- network_acl
- migration_stateful
- disk_state_quota
- storage_ceph_features
- projects_compression
- projects_images_remote_cache_expiry
- certificate_project
- network_ovn_acl
- projects_images_auto_update
- projects_restricted_cluster_target
- images_default_architecture
- network_ovn_acl_defaults
- gpu_mig
- project_usage
- network_bridge_acl
- warnings
- projects_restricted_backups_and_snapshots
- clustering_join_token
- clustering_description
- server_trusted_proxy
- clustering_update_cert
- storage_api_project
- server_instance_driver_operational
- server_supported_storage_drivers
- event_lifecycle_requestor_address
- resources_gpu_usb
- clustering_evacuation
- network_ovn_nat_address
- network_bgp
- network_forward
- custom_volume_refresh
- network_counters_errors_dropped
- metrics
- image_source_project
- clustering_config
- network_peer
- linux_sysctl
- network_dns
- ovn_nic_acceleration
- certificate_self_renewal
- instance_project_move
- storage_volume_project_move
- cloud_init
- network_dns_nat
- database_leader
- instance_all_projects
- clustering_groups
- ceph_rbd_du
- instance_get_full
- qemu_metrics
- gpu_mig_uuid
- event_project
- clustering_evacuation_live
- instance_allow_inconsistent_copy
- network_state_ovn
- storage_volume_api_filtering
- image_restrictions
- storage_zfs_export
- network_dns_records
- storage_zfs_reserve_space
- network_acl_log
- storage_zfs_blocksize
- metrics_cpu_seconds
- instance_snapshot_never
- certificate_token
- instance_nic_routed_neighbor_probe
- event_hub
- agent_nic_config
- projects_restricted_intercept
- metrics_authentication
- images_target_project
- cluster_migration_inconsistent_copy
- cluster_ovn_chassis
- container_syscall_intercept_sched_setscheduler
- storage_lvm_thinpool_metadata_size
- storage_volume_state_total
- instance_file_head
- instances_nic_host_name
- image_copy_profile
- container_syscall_intercept_sysinfo
- clustering_evacuation_mode
- resources_pci_vpd
- qemu_raw_conf
- storage_cephfs_fscache
- network_load_balancer
- vsock_api
- instance_ready_state
- network_bgp_holdtime
- storage_volumes_all_projects
- metrics_memory_oom_total
- storage_buckets
- storage_buckets_create_credentials
- metrics_cpu_effective_total
- projects_networks_restricted_access
- storage_buckets_local
- loki
- acme
- internal_metrics
- cluster_join_token_expiry
- remote_token_expiry
- init_preseed
- storage_volumes_created_at
- cpu_hotplug
- projects_networks_zones
- network_txqueuelen
- cluster_member_state
- instances_placement_scriptlet
- storage_pool_source_wipe
- zfs_block_mode
- instance_generation_id
- disk_io_cache
- amd_sev
- storage_pool_loop_resize
- migration_vm_live
- ovn_nic_nesting
- oidc
- network_ovn_l3only
- ovn_nic_acceleration_vdpa
- cluster_healing
- instances_state_total
- auth_user
- security_csm
- instances_rebuild
- numa_cpu_placement
- custom_volume_iso
- network_allocations
- zfs_delegate
- storage_api_remote_volume_snapshot_copy
- operations_get_query_all_projects
- metadata_configuration
- syslog_socket
- event_lifecycle_name_and_project
- instances_nic_limits_priority
- disk_initial_volume_configuration
- operation_wait
- image_restriction_privileged
- cluster_internal_custom_volume_copy
- disk_io_bus
- storage_cephfs_create_missing
- instance_move_config
- ovn_ssl_config
- certificate_description
api_status: stable
api_version: "1.0"
auth: trusted
public: false
auth_methods:
- tls
auth_user_name: stefanor
auth_user_method: unix
environment:
  addresses: []
  architectures:
  - x86_64
  - i686
  certificate: |
    -----BEGIN CERTIFICATE-----
    MIICATCCAYegAwIBAgIRAOazyG15I/8hVKZntGUeC3EwCgYIKoZIzj0EAwMwMzEc
    MBoGA1UEChMTbGludXhjb250YWluZXJzLm9yZzETMBEGA1UEAwwKcm9vdEBoYXlk
    bjAeFw0yMTAxMDIyMDE2MzFaFw0zMDEyMzEyMDE2MzFaMDMxHDAaBgNVBAoTE2xp
    bnV4Y29udGFpbmVycy5vcmcxEzARBgNVBAMMCnJvb3RAaGF5ZG4wdjAQBgcqhkjO
    PQIBBgUrgQQAIgNiAASpRtrfU40DfHQjRxJMOP+H6eSzd6gRRqjKbz4aY9L2cIHs
    NYDKBPQ1xs6Q3QreixT2/XU4rhTHK1gCk8H0eFJXLvxO8vuVT62e0GFCBWiGHFPk
    IZWWiEMfcQHY5oOsj/ujXzBdMA4GA1UdDwEB/wQEAwIFoDATBgNVHSUEDDAKBggr
    BgEFBQcDATAMBgNVHRMBAf8EAjAAMCgGA1UdEQQhMB+CBWhheWRuhwR/AAABhxAA
    AAAAAAAAAAAAAAAAAAABMAoGCCqGSM49BAMDA2gAMGUCMHOCCGu+ZRT24USQ9qhH
    50aP9fAtCub7kOKa2fciqeyNViVHooIPdlqEY1xDE4JTBAIxAPAOURj6zY+ssStH
    fiqi83/weIevbPFq32Dm04sueh9mRnBmGNds6nh3STU475rnzA==
    -----END CERTIFICATE-----
  certificate_fingerprint: faa18f26d722a99b946ec8c2a6939b8a659c522298b1054760a40d2b142cd9f4
  driver: lxc | qemu
  driver_version: 5.0.3 | 8.1.2
  firewall: nftables
  kernel: Linux
  kernel_architecture: x86_64
  kernel_features:
    idmapped_mounts: "true"
    netnsid_getifaddrs: "true"
    seccomp_listener: "true"
    seccomp_listener_continue: "true"
    uevent_injection: "true"
    unpriv_fscaps: "true"
  kernel_version: 6.5.0-5-amd64
  lxc_features:
    cgroup2: "true"
    core_scheduling: "true"
    devpts_fd: "true"
    idmapped_mounts_v2: "true"
    mount_injection_file: "true"
    network_gateway_device_route: "true"
    network_ipvlan: "true"
    network_l2proxy: "true"
    network_phys_macvlan_mtu: "true"
    network_veth_router: "true"
    pidfd: "true"
    seccomp_allow_deny_syntax: "true"
    seccomp_notify: "true"
    seccomp_proxy_send_notify_fd: "true"
  os_name: Debian GNU/Linux
  os_version: ""
  project: default
  server: incus
  server_clustered: false
  server_event_mode: full-mesh
  server_name: haydn
  server_pid: 3096
  server_version: "0.4"
  storage: btrfs
  storage_version: 6.6.3
  storage_supported_drivers:
  - name: lvm
    version: 2.03.16(2) (2022-05-18) / 1.02.185 (2022-05-18) / 4.48.0
    remote: false
  - name: btrfs
    version: 6.6.3
    remote: false
  - name: dir
    version: "1"
    remote: false

Issue description

If HOME is set to something nonexistent, then the incus CLI will fail, because it can't write .config. sbuild sets this, which breaks incus-backed sbuild.

Does incus need to write .config? Could it fail to write the config gracefully? Or fall back to extracting the home directory from the users database, if HOME is nonexistent?

Relevant config finding code is here:

incus/cmd/incus/main_aliases.go

Lines 162 to 175 in e569070

	// Figure out the config directory and config path
	var configDir string
	if os.Getenv("INCUS_CONF") != "" {
	configDir = os.Getenv("INCUS_CONF")
	} else if os.Getenv("HOME") != "" {
	configDir = path.Join(os.Getenv("HOME"), ".config", "incus")
	} else {
	user, err := user.Current()
	if err != nil {
	return nil
	}
	configDir = path.Join(user.HomeDir, ".config", "incus")
	}

Steps to reproduce

1. $ HOME=/nonexistent incus ls

[stgraber]

@stefanor note that you can use --force-local to avoid using any on-disk config.
This may be a good idea for a use case like sbuild.

[stgraber]

Incus actually does fetch the user's home directory from /etc/passwd but only if the env variable isn't set. If HOME is set, then it's expected to exist.

[stgraber]

I've changed our logic a bit to validate that the home directory actually exists at every step.
If the path in HOME doesn't exist and the user's home dir from /etc/passwd also doesn't exist, then incus will behave as if --force-local was passed.

[stefanor]

That sounds a lot more robust, thanks!