These parameters are meant to be applied to the `./compile.sh` command. They are **all** optional. They can also be added to your [build configuration file](/Developer-Guide_Build-Preparation/#providing-build-configuration) to save time. Default values are marked **bold** if applicable.
- **CLEAN_LEVEL** (comma-separated list): defines what should be cleaned. Default value is `"make,debs"` - clean sources and remove all packages. Changing this option can be useful when rebuilding images or building more than one image
- yes: build bare CLI image suitable for application deployment. This option is **not compatible** with `BUILD_DESKTOP="yes"` and `BUILD_EXTERNAL="yes"`
- yes: prompt right before the compilation starts to make changes to the source code for both U-Boot and kernel. From these changes patch files will be created and placed in `output` directory. If you want these patches included in a normal run (without CREATE_PATCHES to say) these files need to be copied to the appropriate directories. Also see [user provided patches](https://docs.armbian.com/Developer-Guide_User-Configurations/#user-provided-patches).
- set to `master` to compile from the master branch (default)
- set to another "branchname" to compile from any other branch available. Check [here](https://github.com/armbian/build/branches) for available branches
- **Note:** This function might not work well with all distributions. Debian Buster and Stretch were tested. For building under Docker you have to use privileged mode which can be enable in `userpatches/config-docker`.
- **Warning:** This feature was added as community contribution and mostly functional. Under some circumstances though the prompt will not be shown. Therefore it should be considered experimental. Check [here](https://github.com/armbian/build/commit/681e58b6689acda6a957e325f12e7b748faa8330) and [here](https://github.com/armbian/build/issues/1183)
- **Hint:** If you want to do the encryption part from scratch check out [this](https://forum.armbian.com/topic/15618-full-root-filesystem%C2%A0encryption%C2%A0on-an-armbian-system-new-replaces-2017-tutorial-on-this-topic/) forum post.
- **BRANCH** ( `legacy` | `current` | `edge` ): set kernel and U-Boot branch manually to skip dialog prompt; some options may not be available for all devices
- **RELEASE** ( `stretch` | `buster` | `bullseye` | `bionic` | `focal` | `hirsute` ): set OS release manually to skip dialog prompt; use this option with `KERNEL_ONLY=yes` to create board support package
- **SKIP_EXTERNAL_TOOLCHAINS** ( yes | **no** ) don't download and use Linaro toolchains, by default placed in cache/toolchain (and configurable with **ARMBIAN_CACHE_TOOLCHAIN_PATH**)
- **USE_MAINLINE_GOOGLE_MIRROR** ( yes | **no** ): use `googlesource.com` mirror for downloading mainline kernel sources, may be faster than `git.kernel.org` depending on your location
- **USE_GITHUB_UBOOT_MIRROR** ( yes | **no** ): use unofficial Github mirror for downloading mainline U-Boot sources, may be faster than `git.denx.de` depending on your location
- **OFFLINE_WORK** ( yes | **no** ): skip downloading and updating sources as well as time and host check. Set to "yes" and you can collect packages without accessing the internet
- **FORCE_USE_RAMDISK** ( yes | no ): overrides autodetect for using tmpfs in new debootstrap and image creation process
- **FIXED_IMAGE_SIZE** ( `integer` ): create image file of this size (in megabytes) instead of minimal
- **ROOTFS_TYPE** ( **ext4** | f2fs | btrfs | xfs | nfs | fel ): create image with different root filesystems instead of default `ext4`. Requires setting `FIXED_IMAGE_SIZE` to something smaller than the size of your SD card for `F2FS`
- **BTRFS_COMPRESSION** ( lzo | none | **zlib** | zstd ): when choosing `ROOTFS_TYPE=btrfs` select `btrfs` filesystem compression method and compression level. By default the compression is `zlib`.
When selecting `zstd` or setting zlib compression level(`zlib:[1-9]`) user must ensure kernel version is **>=4.14.x**.
When selecting zstd compression level (`zstd:[1-15]`) both the host and the target kernel version must be **>=5.1.x** since kernel started supporting zstd compression ratio only from 5.1 on.
*Note:* The script does not check the legality of input variable (compression ratio). Input like `zlib:1234` is legal to the script but illegal to the kernel. Beware that setting this option does affect image creation only (shrinking disk size) and will not adjust `/etc/fstab` so it is up to the user to later edit `/etc/fstab` if compression in daily operation is also wanted (beware of serious performance penalties with random IO patterns and heavy compression algorithms!).
- **ROOT_FS_CREATE_ONLY** ( `FORCE` ): set to skip rootfs download and create locally
- **EXTRAWIFI** ( **yes** | no ): include several drivers for [WiFi adapters](https://github.com/armbian/build/blob/1914066729b7d0f4ae4463bba2491e3ec37fac84/lib/compilation-prepare.sh#L179-L507)
- **WIREGUARD** ( **yes** | no ): include Wireguard for kernels before it got upstreamed to mainline. Will lose functionality soon.
- **AUFS** ( **yes** | no ): Include support for [AUFS](https://en.wikipedia.org/wiki/Aufs)
