Environment Variables

Cubic reads the following environment variables from the host. None of them is required. Each one either overrides a default or tells Cubic something about the host it runs on.

To pass a variable of the host into a VM instance instead, see Forward Environment Variables.

QEMU and Firmware

These variables override the automatic detection described in QEMU and Firmware Detection.

Variable	Description
`CUBIC_QEMU_DIR`	Directory of the QEMU install. Placed at the front of the search list for the QEMU binaries, and used to locate the `share/qemu/firmware` descriptors.
`CUBIC_QEMU_FW_AMD64`	Path to a specific amd64 UEFI firmware (CODE) file. Overrides the descriptor based firmware selection for amd64 VM instances.
`CUBIC_QEMU_FW_ARM64`	Path to a specific arm64 UEFI firmware (CODE) file. Overrides the descriptor based firmware selection for arm64 VM instances.
`PATH`	Searched for `qemu-system-x86_64`, `qemu-system-aarch64` and `qemu-img` after `CUBIC_QEMU_DIR` and before the built in default directories.
`XDG_CONFIG_HOME`	Adds `$XDG_CONFIG_HOME/qemu/firmware` to the firmware descriptor search, falling back to `$HOME/.config/qemu/firmware`. This variable points at the QEMU configuration, not at any Cubic configuration.

File Locations

These variables decide where Cubic keeps VM instances and downloaded images. File Locations shows the resulting paths.

Variable	Description
`HOME`	Base directory on macOS. Fallback for the data and cache directory on Linux. Also the `.ssh` directory Cubic searches for your SSH public keys.
`XDG_DATA_HOME`	Directory of the VM instances on Linux. Falls back to `$HOME/.local/share`.
`XDG_CACHE_HOME`	Directory of the image cache on Linux. Falls back to `$HOME/.cache`.
`LOCALAPPDATA`	Directory of the VM instances on Windows. Required on Windows.
`TEMP`	Directory of the image cache on Windows. Required on Windows.
`SNAP_USER_COMMON`	Directory of the VM instances in the snap package. Takes precedence over `XDG_DATA_HOME`. The snap sets it for you.
`SNAP_REAL_HOME`	Real home directory of the user in the snap package. Its `.ssh` directory is searched for your SSH public keys. The snap sets it for you.
`SNAP`	Marks a run inside the snap package. Cubic then suggests `sudo snap connect cubic:kvm` when hardware acceleration is missing. The snap sets it for you.

User and Terminal

Variable	Description
`USER`, `LOGNAME`, `USERNAME`	Default user name of a new VM instance. The first variable that is set wins. A value of `root` or an unusable name falls back to `cubic`. Use `cubic create --user` to set the name per VM instance.
`TERM`	Terminal type requested for the SSH session of `cubic ssh` and `cubic exec`. Falls back to `xterm`.
`NO_COLOR`	Turns off colored output when it is set to any value, including an empty one. See no-color.org.

Network Proxy

Cubic downloads images over HTTPS and honors the usual proxy variables. Each name also works in lower case, such as https_proxy. The upper case name wins when both are set.

Variable	Description
`HTTPS_PROXY`	Proxy URL for HTTPS requests, such as `http://proxy.example.com:3128`. This is the one image downloads use.
`HTTP_PROXY`	Proxy URL for plain HTTP requests.
`ALL_PROXY`	Proxy URL for both. A matching `HTTP_PROXY` or `HTTPS_PROXY` wins.
`NO_PROXY`	Comma separated list of hosts that bypass the proxy, such as `localhost,10.0.0.0/8`. A single `*` bypasses the proxy for every host.

SSL_CERT_FILE and SSL_CERT_DIR have no effect, because Cubic ships its own root certificates. Use a Proxy for Downloads covers the platform differences and what to do when a proxy terminates TLS itself.

Variables Cubic Sets

Cubic sets these variables for the QEMU process it starts. Setting them on the host has no effect.

Variable	Description
`PATH`	Search list Cubic built for the QEMU binaries.
`QEMU_MODULE_DIR`	Module directory of the QEMU install Cubic found.