Configuring in-place upgrade: envars

The actor configuration is WIP.

docs/source/configuring-ipu.md

@@ -1,2 +1,99 @@
 # Configuring in-place upgrade
-TBD
+Sometimes it is necessary to tweak some parts of the upgrade for it to be successful. There are currently 2 mechanisms in Leapp for configuration: environment variables and actor configuration. The former are usually used for options affecting the entire upgrade or enabling debug and experimental features. Actor configuration is used to configure a single actor.
+
+## Environment variables
+Below is a list of the general and development variables available.
+### General variables
+
+#### LEAPP_DATABASE_FORCE_SYNC_ON
+If set to `1`, Leapp will explicitly enable synchronization on the SQLite database. Enabling the synchronization has negative impact on the performance (sometimes very negative). However, it is more reliable in case of extreme situations (e.g. lost power). Note the synchronization is nowadays switched off by default only during the phases executed before the reboot of the system to the upgrade environment, which we consider safe. As a result, we do not expect that someone would want to use this option now.
+
+#### LEAPP_DEBUG
+Enables debug logging. Equivalent to --debug, which takes precedence.
+
+#### LEAPP_ENABLE_REPOS
+Specify repositories (repoids) split by comma, that should be used during the in-place upgrade to the target system. It‘s overwritten automatically in case the --enablerepo option is used. It‘s recommended to use the --enablerepo option instead of the envar.
+
+#### LEAPP_GRUB_DEVICE
+Overrides the automatically detected storage device with GRUB core (e.g. /dev/sda).
+
+#### LEAPP_NOGPGCHECK
+Set to 1 to disable RPM GPG checks (same as yum/dnf –nogpgckeck option). It‘s equivalent to the --nogpgcheck leapp option.
+
+#### LEAPP_NO_INSIGHTS_REGISTER
+If set to `1`, Leapp does not register the system into Red Hat Insights automatically. It‘s equivalent to the --no-insights-register leapp option.
+
+#### LEAPP_NO_NETWORK_RENAMING
+If set to `1`, the actor responsible to handle NICs names ends without doing anything. The actor usually creates UDEV rules to preserve original NICs in case they are changed. However, in some cases it‘s not wanted and it leads in malfunction network configuration (e.g. in case the bonding is configured on the system). It‘s expected that NICs have to be handled manually if needed.
+
+##### LEAPP_NO_RHSM
+If set to `1`, Leapp does not use Red Hat Subscription Management for the upgrade. It‘s equivalent to the --no-rhsm leapp option.
+
+#### LEAPP_NO_RHSM_FACTS
+If set to `1`, Leapp does not store migration information using Red Hat Subscription Manager. It‘s equivalent to the --no-rhsm-facts leapp option.
+
+#### LEAPP_OVL_SIZE
+For any partition that uses XFS with the `ftype` option set to `0`, Leapp is creating a file of a specific size in order to proceed with the upgrade. By default, the size of that file is 2048 MB. In case the size needs to be increased, Leapp informs you in the pre-upgrade report that the environment variable needs to be specified.
+
+#### LEAPP_PROXY_HOST
+If set, leapp will use this proxy to fetch necessary data files in case they are missing. The used protocol (http:// or https://) must be specified.
+
+#### LEAPP_SERVICE_HOST
+Overrides the host of the service to which leapp connects to fetch necessary data files in case they are missing. The used protocol (http:// or https://) must be specified. Defaults to https://cert.cloud.redhat.com.
+
+#### LEAPP_TARGET_ISO
+Set the path to the target OS ISO image that should be used for the IPU. It‘s equivalent to the --iso leapp option.
+
+#### LEAPP_TARGET_PRODUCT_CHANNEL
+The alternative to the --channel leapp option. As a parameter accepts a channel acronym. E.g. `eus` or `e4s`. For more info, see the leapp preupgrade --help. In case the beta channel is required, use the `LEAPP_DEVEL_TARGET_PRODUCT_TYPE` envar instead.
+
+#### LEAPP_UNSUPPORTED
+Necessary to use in case you use any envar with the LEAPP_DEVEL prefix (see the list in the next section) and in case you use the –whitelist-experimental option for the Leapp tool.
+
+#### LEAPP_VERBOSE
+Enables debug logging. Equivalent to --verbose, which takes precedence.
+
+
+### Development variables
+```{note}
+To use development variables, the LEAPP_UNSUPPORTED variable has to be set.
+```
+
+#### LEAPP_DEVEL_DATABASE_SYNC_OFF
+If set to `1`, leapp will disable explicit synchronization on the SQLite database. The positive effect is significant speedup of leapp execution, however it comes at the cost of risking a corrupted database, so it is currently used for testing / development purposes only.
+
+#### LEAPP_DEVEL_DM_DISABLE_UDEV
+Setting the environment variable provides a more convenient way of disabling udev support in libdevmapper, dmsetup and LVM2 tools globally without a need to modify any existing configuration settings. This is mostly useful if the system environment does not use udev.
+
+#### LEAPP_DEVEL_INITRAM_NETWORK
+You can specify one of the following values: `network-manager`, `scripts`. The `scripts` value is used for a legacy dracut module when the network is not handled by NetworkManager. Using the option allows experimental upgrades, bringing up the networking inside the upgrade initramfs environment (upgrade phases after the first reboot). It also enables the upgrade e.g. when a network based storage is used on the system. Currently it works only for the most simple configurations (e.g. when only 1 NIC is present, no rdma, no bonding, ...). Network based storage is not handled anyhow during the upgrade, so it‘s possible that the network based storage will not be correctly initialized and usable as expected).
+
+#### LEAPP_DEVEL_KEEP_DISK_IMGS
+If set to `1`, leapp will skip removal of disk images created for source OVLs. This is handy for debugging and investigations related to created containers (the scratch one and the target userspace container).
+
+#### LEAPP_DEVEL_RPMS_ALL_SIGNED
+Leapp will consider all installed pkgs to be signed by RH - that affects the upgrade process as by default Leapp upgrades only pkgs signed by RH. Leapp takes care of the RPM transaction (and behaviour of applications) related to only pkgs signed by Red Hat. What happens with the non-RH signed RPMs is undefined.
+
+#### LEAPP_DEVEL_SKIP_CHECK_OS_RELEASE
+Do not check whether the source RHEL version is a supported one.
+
+#### LEAPP_DEVEL_SOURCE_PRODUCT_TYPE
+By default the upgrade is processed from the GA (general availability) system using GA repositories. In case you need to do the in-place upgrade from a Beta system, use the variable to tell which of those you would like to use. The value is case insensitive and the default value is `ga`. Expected values: `ga`, `beta`.
+
+#### LEAPP_DEVEL_TARGET_PRODUCT_TYPE
+LEAPP_DEVEL_TARGET_PRODUCT_TYPE is an analogy to LEAPP_DEVEL_SOURCE_PRODUCT_TYPE for the target system and an extension to the LEAPP_TARGET_PRODUCT_CHANNEL. If used, it replaces any value set via the --channel option or through the LEAPP_TARGET_PRODUCT_CHANNEL environment variable. It consumes the same set of values as the --channel option, and can be extended with the value `beta`. This is the only way how to perform the in-place upgrade to a beta version of the target system using subscription-manager.
+
+#### LEAPP_DEVEL_TARGET_RELEASE
+Change the default target RHEL version. Format: `MAJOR.MINOR`.
+
+#### LEAPP_DEVEL_USE_PERSISTENT_PACKAGE_CACHE
+Caches downloaded packages when set to `1`. This will reduce the time needed by leapp when executed multiple times, because it will not have to download already downloaded packages. However, this can lead to a random issues in case the data is not up-to-date or when setting or repositories change. The environment variable is meant to be used only for the part of the upgrade before the reboot and has no effect or use otherwise.
+
+
+## Actor configuration
+```{warning}
+Actor configuration is currently a preview of the feature, it might change in future releases.
+```
+The actor configuration is to be placed in the `/etc/leapp/actor_conf.d/` directory. An actor configuration is a file in YAML format.
+
+To define configuration options on your own actor refer to this tutorial TODO link.