Environment variables

Every environment variable Kiln reads, with accepted values, where it applies, and how it ranks against the config file.

Kiln reads environment variables once at startup and never re-reads them. Unless noted otherwise, only a non-empty value has any effect; an empty value is the same as an unset one.

Server variables

Variable	Effect	Values	Precedence
`KILN_LISTEN`	Overrides `server.listen`	Host and port	Above the config file
`KILN_PUBLIC_BASE_URL`	Overrides `server.public_base_url`	Absolute URL; a trailing slash is trimmed	Above the config file
`KILN_DATA_DIR`	Overrides `server.data_dir`	Directory path	Above the config file
`KILN_TOKEN_PRIVATE_KEY`	Overrides `auth.token_private_key`	Ed25519 private key PEM	Above the config file
`KILN_TOKEN_PRIVATE_KEY_FILE`	Overrides `auth.token_private_key_file`	File path	Above the config file
`KILN_TOKEN_PUBLIC_KEY`	Overrides `auth.token_public_key`	Ed25519 public key PEM	Above the config file
`KILN_TOKEN_PUBLIC_KEY_FILE`	Overrides `auth.token_public_key_file`	File path	Above the config file
`KILN_RESOURCE_MODE`	Overrides `server.resource_mode`	`auto`, `performance`, `constrained`	Above the config file
`KILN_RESOURCE_MEMORY_MB`	Overrides detected memory	Positive integer, in MiB	Above autodetection
`KILN_RESOURCE_CPUS`	Overrides detected CPU capacity	Positive integer core count	Above autodetection
`KILN_RUNTIME_VARIANT`	Declares the runtime variant	`core`, `full`; unset means `standalone`	No config equivalent
`KILN_LOG_LEVEL`	Overrides `logging.level`	`debug`, `info`, `warn`, `error`	Above the config file
`KILN_LOG_FORMAT`	Overrides `logging.format`	`text`, `json`	Above the config file
`KILN_LOG_COLOR`	Overrides `logging.color`	`auto`, `always`, `never`	Above the config file
`KILN_DEFAULT_PACKAGER_ENGINE`	Supplies a fallback for `packager.engine`	`auto`, `native`, `ffmpeg`	Below the config file
`KILN_PLAY_OPEN`	Drives `security.play_require_auth`	`1`, `true`, `TRUE` disable auth; `0`, `false`, `FALSE` require it	The environment decides
`GOMEMLIMIT`	Go runtime soft memory limit	Any size the Go runtime accepts, such as `128MiB`	Always wins
`GOGC`	Go garbage-collection target percentage	Any value the Go runtime accepts, such as `100` or `off`	Prevents resource adaptation from setting the GC target
`NO_COLOR`	Disables log coloring	Any non-empty value	Only affects `auto`

Precedence rules

Most variables are applied after parsing and before defaults are filled in, so the usual order is environment above config file above built-in default. The following are exceptions to that order.

KILN_DEFAULT_PACKAGER_ENGINE only applies when the config is silent

It is read while defaults are filled in, and only when packager.engine is empty. Any value in the config file wins outright. Once adopted it still goes through the normal validation, so a value outside auto, native, ffmpeg fails startup. The Lite variant sets the variable to native before loading the config if it is unset, and refuses any engine other than native.

KILN_PLAY_OPEN overrides the playback auth setting

1, true, or TRUE sets security.play_require_auth to false; 0, false, or FALSE sets it to true; any other value leaves the setting alone. With the variable unset the config file decides: play_require_auth is an optional boolean that defaults to requiring a credential, and an explicit false turns playback authentication off. Either way, disabling it belongs in debugging environments only.

GOMEMLIMIT always beats the config and the automatic plan

Kiln sets a Go soft memory limit itself only when server.memory_limit_mb is positive and GOMEMLIMIT is unset. Whenever GOMEMLIMIT is present the runtime honors it, and neither the configured value nor the profile budget chosen by resource adaptation touches that setting.

GOGC overrides the profile GC target

When GOGC is unset, Kiln adjusts the Go garbage-collection target for the active resource profile. When the variable is present, Kiln leaves it unchanged and the Go runtime interprets the value.

KILN_RESOURCE_MEMORY_MB and KILN_RESOURCE_CPUS replace detection, not configuration

Neither variable overrides a config key. They replace the result of resource detection, which resource adaptation then uses to pick a profile. Only positive integers are accepted; unparsable, non-positive, or out-of-range values are ignored and detection stands. They are useful on hosts where detection is wrong, or to reproduce a specific profile. With server.resource_mode = "performance" adaptation is skipped entirely, so neither variable has any effect.

NO_COLOR only matters in auto mode

Coloring looks at logging.color or KILN_LOG_COLOR first: always forces color and never consults NO_COLOR, never disables it, and auto (the default) colors only when the output is a terminal device and NO_COLOR is unset. JSON-formatted logs are never colored.

KILN_RUNTIME_VARIANT is self-identification only

Unset means standalone. core and full are valid; anything else logs a warning at startup and is treated as standalone. The official container images already set it, so it rarely needs to be set by hand. See Distribution variants for a capability comparison.

Install script variables

The install script reads a separate set of variables that only affect installation and upgrades, not the running server.

Variable	Effect
`KILN_YES`	`1` skips every interactive confirmation
`KILN_VERSION`	Pins the version to install
`KILN_VARIANT`	Selects `full` or `lite`; anything else exits with an error
`KILN_INSTALL_DIR`	Sets the install directory
`KILN_MIRROR`	Sets the download mirror
`KILN_NO_MIRROR`	`1` disables mirrors
`KILN_LANG`	Forces the script output language
`KILN_DRY_RUN`	`1` walks through the flow without writing anything

The install script honors NO_COLOR as well. See Install script for usage.