- **.sha file** for download verification (optional)
- **.asc file** for image authentication (optional)
!!! question "How to check download authenticity?"
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. `sudo 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/):
It is safe to ignore the message `WARNING: This key is not certified with a trusted signature!`.
!!! question "How to check download integrity?"
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.
while on Linux/macOS, in the directory in which you have downloaded the files ,you would do this
- **edge** is as the name implies cutting-edge fresh / development / latest stable. It is only automatically tested and can break at any time. Recommended for experienced users.
- **legacy** is old stable current kernel. Use if either _current_ is not available or something does not work well with it.
The level of kernel support however always depends on the board family. If in your specific case something does not work well, you are always free to try an image with an other kernel included or change kernel within [armbian-config](/User-Guide_Armbian-Config).
Rolling releases are suitable for Linux enthusiasts who want cutting edge packages and have the skills to fix damage that a bad update might cause. If you want stability in a production environment or low headaches as a novice user, skip rolling releases. They are only at, build and ship, Debian testing / Arch / Manjaro / Suse Tumbleweed / Kali / Gentoo support quality level!
**Do not use** rollling or edge images in a productive environment. Their purpose is testing and providing constructive [feedback to developers](https://forum.armbian.com/forum/4-development/).
**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** to your microSD card. Using [USBImager](https://gitlab.com/bztsrc/usbimager) on all platforms is recommended since, unlike other tools, it can validate written data **saving you from corrupted SD card contents**. Due to known issues using BalenaEtcher is not recommended at this time.
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.
We recommend at least A1 rated SD-Cards ([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.
Armbian provides firmware package freeze to give you an option to upgrade all packages but firmware. This prevents unplesant surprises on functionality regressions that comes with kernel upgrades. To enable / disable this feature, look for `Enable Armbian kernel/firmware upgrades / Disable Armbian kernel upgrades` within [armbian-config](/User-Guide_Armbian-Config).
When a new userspace is out, we recommend to start with a fresh image. However, it is possible to upgrade, but the process is largerly in the domain of underlaying Debian or Ubuntu user space. However we provide experimental `Distribution upgrades` within [armbian-config](/User-Guide_Armbian-Config)
Follow bug reporting form available [here](https://armbian.com/bugs/) and learn how to collect necessary information and where provide to put your report depending on type of issue. Reports lacking fundamental diagnostics are ignored.
