- **legacy** is either a vendor provided kernel or an old LTS mainline kernel. Use if either _current_ is not available or something does not work well.
- **current** is usually following current mainline LTS kernel and considered fully supported and can bring up features video acceleration for example
- **edge** is as the name implies cutting-edge and usually following the latest mainline kernel or 3rd party development branch. Untested, unstable, can break at any time, for experienced users only.
**Do not use** testing or edge images in a productive environment. We do appreciate your constructive [feedback to developers](https://forum.armbian.com/forum/4-development/).
All our images are digitally signed and therefore it is possible to check their authenticity. You need to issue these commands (Linux/macOS, you might need to install dependencies first, eg. `apt-get install gnupg ` on Debian/Ubuntu or `brew install gnupg ` on macOS. on windows install the current simple gnupg [Gnupg](https://gnupg.org/download/):
Since it might happen that your download got somehow corrupted we integrate a checksum/hash for the image. You can compare the image's SHA-256 hash with the one contained in the `sha256sum.sha` file.
On Windows, you can download and use the [QuickHash GUI](https://www.quickhash-gui.org/download/quickhash-v3-1-0-windows/) and follow the instructions in the gui.
**Important note:** Make sure you use a **good, reliable and fast** SD card. If you encounter boot or stability troubles in over 95 percent of the time it is either insufficient power supply or related to SD card (bad card, bad card reader, something went wrong when burning the image, card too slow to boot -- 'Class 10' highly recommended!). Armbian can simply not run on unreliable hardware so checking your SD card with either [F3](https://fight-flash-fraud.readthedocs.io/en/stable/) or [H2testw](https://www.heise.de/download/product/h2testw-50539) is mandatory if you run in problems. Since [counterfeit SD cards](https://www.happybison.com/reviews/how-to-check-and-spot-fake-micro-sd-card-8/) are still an issue checking with F3/H2testw directly after purchase is **highly recommended**.
Write the **.xz compressed image** with a tool [USBImager](https://gitlab.com/bztsrc/usbimager) or [balenaEtcher](https://www.balena.io/etcher/) on all platforms since, unlike other tools, either can validate written data **saving you from corrupted SD card contents**.
Also important: Most SD cards are only optimised for sequential reads/writes as it is common with digital cameras. This is what the *speed class* is about. The SD Association defined [*Application Performance Class*](https://www.sdcard.org/developers/overview/application/index.html) as a standard for random IO performance.
At the time of this writing A1 and A2 cards are only widely available from SanDisk. Armbian recommends A1 rated SD-Cards **only** now ([A2 rated cards need yet lacking driver support and therefore show lower overall and especially random IO performance](https://github.com/ThomasKaiser/Knowledge/blob/master/articles/A1_and_A2_rated_SD_cards.md)). For example:
In case you chose an SD card that was already in use before please consider resetting it back to 'factory default' performance with [SD Formatter](https://www.sdcard.org/downloads/formatter/) before burning Armbian to it ([explanation in the forum](https://forum.armbian.com/topic/3776-the-partition-is-not-resized-to-full-sd-card-size/&do=findComment&comment=27413)). Detailed information regarding ['factory default' SD card performance](https://forum.armbian.com/topic/954-sd-card-performance/page/3/&tab=comments#comment-49811).
First boot will log you automatically on HDMI or serial console while for SSH login you need to login as **root** and use password **1234**. You will be prompted to change this password. You will then be asked to create a normal user account that is sudo enabled (beware of default QWERTY keyboard settings at this stage). Please use [this tool](https://angryip.org/), to find your board IP address.
## How to upgrade distribution (like Focal to Jammy or Bullseye to Bookworm)?
Fire up `armbian-config` to freeze your firmware packages (if not frozen already, select `System` and `Freeze`).
Then follow generic upgrade instructions specific to your userspace:
- Like for Debian: [https://www.debian.org/releases/bookworm/arm64/release-notes/ch-upgrading.en.html](https://www.debian.org/releases/bookworm/arm64/release-notes/ch-upgrading.en.html)
- Or Ubuntu: launch `do-release-upgrade`
__Attention:__ Userspaces distribution upgrades are neither tested nor supported. Therefore Armbian cannot provide support if something goes wrong.
On Allwinner devices after switching to boot from NAND or eMMC clearing the boot loader signature on the SD card is recommended: `dd if=/dev/zero of=/dev/mmcblkN bs=1024 seek=8 count=1` (replace `/dev/mmcblkN` with the correct device node -- in case you run this directly after `armbian-install` without a reboot in between then it's `/dev/mmcblk0`). When booting from eMMC to get SD cards auto-detected on Allwinner legacy images please consider changing `mmc0`'s `sdc_detmode` from 3 to 1 in the board's fex file (see [here](https://forum.armbian.com/topic/1702-orange-pi-plus-2e-where-is-16ghz-and-sd/?tab=comments#comment-13163) for details).
## How to install to NAND?
While in theory writing to NAND should still be possible using `armbian-installer`, this requires running a very old 3.4.y kernel which Armbian as dropped support for several years ago. Therefore this feature is to be considered as deprecated and no support for either 3.4.y systems or NAND installations will be provided.
