fastboot get active slot fastboot flashes the current slot on an A/B device
fastboot get active slot active - Fastbootreboot recovery slot Mastering Fastboot Get Active Slot: A Comprehensive Guide for Android Developers and Enthusiasts
Fastbootd Navigating the intricacies of Android's A/B partition scheme and the fastboot command-line tool can be crucial for developers, enthusiasts, and anyone looking to maintain or modify their devices20181225—I am trying to boot from IMX6 bootloader, but couldn't able to automate theslotselection based on OTA update. A fundamental operation within this process is understanding how to get active slot information, which dictates which partition the device will boot from[Recovery] Switch slots on A/B device r/LineageOS This article will delve deep into the `fastboot getvar current-slot` command, its significance, common troubleshooting steps, and how it relates to the broader Android A/B update systemAndroid fastboot 查詢當使用的a/b槽
Understanding Android's A/B Partitioning and Slots
Android devices utilizing A/B partitioning employ a dual-slot system (Slot A and Slot B) to facilitate seamless Over-The-Air (OTA) updatesHow does android bootloader know it has to boot from Slot This means that while your device is running on one slot, the other slot can be updated in the backgroundRun fastboot getvar current-slotto get the active slot in fastboot. Run fastboot set_active {a or b} to change the active slot. Do not forget to erase the Once the update is complete, the device can then switch to the newly updated slot upon the next rebootThis page contains binary image files that allow you to restore your Nexus or Pixel device's original factory firmware. This approach significantly reduces downtime and the risk of a failed update bricking the deviceAfter the OTA update is successful, AOSP marks the targetslotB toactive. Now, when the next boot happens, the device boots fromslotB. The system intelligently manages which slot is active and will be used for bootingAndroid Fastboot Mode Commands with Examples
The `fastboot getvar current-slot` Command Explained
The primary command for querying the active boot partition is `fastboot getvar current-slot`After the OTA update is successful, AOSP marks the targetslotB toactive. Now, when the next boot happens, the device boots fromslotB. This command, when executed in a fastboot environment, queries the device's bootloader for information about the currently designated active slotGrapheneOS Frequently Asked Questions The output will typically be either `a` or `b`, indicating which of the two partitions (Slot A or Slot B) is currently set to boot202394—This command provides information about theactive slotfrom which the device is currently booting. user $fastbootgetvar current-slot. Dump
To use this command, your device needs to be in fastboot modeAndroid fastboot 查詢當使用的a/b槽 This is usually achieved by powering off your device and then booting it while holding down a specific key combination (often Volume Down + Power, but this can vary by manufacturer)After the OTA update is successful, AOSP marks the targetslotB toactive. Now, when the next boot happens, the device boots fromslotB. Once in fastboot mode, you can connect it to your computer via USB and execute the command in your terminal:
```bash
fastboot getvar current-slot
```
The result will be displayed directly in your terminal, for example:
```
current-slot: a
Finished2025122—By default,fastboot flashes the current slot on an A/B device. If the update package also contains images for the other, non-current slot, Total time: 0Installation | KernelSU001s
```
This indicates that your device is currently set to boot from Slot AThis page contains answers to frequently asked questions aboutGrapheneOS. It's not an overview of the project or a list of interesting topics about GrapheneOS. Users have also reported successful use of `fastboot getvar all` to retrieve a comprehensive list of variables, which includes the `current-slot`Android/Fastboot - Gentoo Wiki
Why Querying the Active Slot is Important
Understanding the active slot is vital for several scenarios:
* OTA Updates: After an OTA update is successfully installed, the system typically marks the target slot (eAndroid fastboot 查詢當使用的a/b槽gI was able to fix this withfastboot --set-active=afollowed immediately by fastboot flash boot boot.img and all the other partitions., Slot B if the update was performed on it) as activeThis page contains answers to frequently asked questions aboutGrapheneOS. It's not an overview of the project or a list of interesting topics about GrapheneOS. Knowing the current slot helps verify this process20201213—I tried everything factory reset, reinstall /e/ on the not workingslot, unlock, lock the bootloader, install /e/ withactive slotA, install /
* Troubleshooting Boot Issues: If your device is experiencing boot problems, particularly after an update or manual flashing, checking the active slot can reveal if the device is attempting to boot from a corrupted or misconfigured slotAndroid Fastboot Mode Commands with Examples This can lead to errors like "fastboot: error: Failed to identify current slot" or "current-slot:no bootable slotRun fastboot getvar current-slotto get the active slot in fastboot. Run fastboot set_active {a or b} to change the active slot. Do not forget to erase the "
* Manual Flashing: When manually flashing images, such as a boot image or recovery image, you might need to ensure you're flashing to the correct slot, especially if you intend to switch slots subsequentlyGrapheneOS Frequently Asked Questions
* System Stability: For devices running custom ROMs like GrapheneOS or LineageOS, properly managing and understanding the active slot is crucial for overall system stability and successful updatesHow does android bootloader know it has to boot from Slot
Common `fastboot` Commands Related to Slot Management
While `fastboot getvar current-slot` tells you which slot is active, other fastboot commands allow you to manage it:
* Setting the Active Slot:
* `fastboot --set-active=a` or `fastboot --set-active=b`: This command directly changes the active slotGrapheneOS Frequently Asked Questions For example, `fastboot --set-active=a` will set Slot A as the active boot partitionFactory Images for Nexus and Pixel Devices
* `fastboot set_active
* Flashing to the Current Slot: By default, fastboot flashes the current slot on an A/B deviceHyperOS 3.0 STABLE RELEASE | Page 24 - Xiaomi.eu This means if Slot A is active, a standard `fastboot flash boot boot20201213—I tried everything factory reset, reinstall /e/ on the not workingslot, unlock, lock the bootloader, install /e/ withactive slotA, install / img` command will write the `bootHyperOS 3.0 STABLE RELEASE | Page 24 - Xiaomi.euimg` to Slot A's boot partition[Recovery] Switch slots on A/B device r/LineageOS
* Switching Slots: While there isn't a direct `fastboot switch-slots` command, you can achieve this by first finding the non-active slot and then setting it as active20241031—Set Active Slot (for devices with A/B Partitions),fastboot –set-active=
Troubleshooting Common `fastboot` Slot Errors
Encountering errors when dealing with slots is not uncommon20201213—I tried everything factory reset, reinstall /e/ on the not workingslot, unlock, lock the bootloader, install /e/ withactive slotA, install / Here are a few common issues and their potential solutions:
* `fastboot: error: Failed to identify current slot` or `current-slot:no bootable slot`:
* Cause: This often occurs when the bootloader cannot determine a valid bootable slotFactory Images for Nexus and Pixel Devices This could be due to a corrupted A/B configuration or an incomplete updateYou can consider usingfastbootboot KernelSU's GKI kernel togettemporary root and install the manager, and then use this option. This is also the main way to
* Solution: Try explicitly setting an active slotAfter the OTA update is successful, AOSP marks the targetslotB toactive. Now, when the next boot happens, the device boots fromslotB. For example, if you suspect Slot A might be problematic, try setting Slot B as active: `fastboot --set-active=b`Cannot switch slots - Fairphone If that fails, attempt `fastboot --set-active=a`20241031—Set Active Slot (for devices with A/B Partitions),fastboot –set-active=
* `Bad Buffer Size` during `fastboot boot`:
* Cause: This error, encountered by some users on devices like Xiaomi, can occur when trying to temporarily boot an image (like TWRP) using `fastboot boot`You can consider usingfastbootboot KernelSU's GKI kernel togettemporary root and install the manager, and then use this option. This is also the main way to
* Solution: Making the other slot active before attempting to `fastboot boot` has been a reported fixGrapheneOS Frequently Asked Questions For instance, if Slot A is the default, try setting Slot B as active (`fastboot --set-active=b`) and then proceed with `fastboot boot`Kali NetHunter Pro | Kali Linux Documentation
* Updates Not Taking Effect:
* Cause: If you've performed an OTA update but the device doesn't boot into the new version, it might be that the wrong slot was marked as active20201213—I tried everything factory reset, reinstall /e/ on the not workingslot, unlock, lock the bootloader, install /e/ withactive slotA, install /
* Solution: Use `fastboot getvar current-slot` to check which slot is active20251016—In this comprehensive tutorial, we will show you detailed steps to fix thefastboot error Failed to identify currentslot. If it's not the one that was updated, use `fastboot --set-active=
Advanced Concepts and Related Tools
* `bootctl`: On newer Android versions, the `bootctl` command-line tool offers more granular control over boot slot management and can be used as an alternative or complementary tool in some scenariosFactory Images for Nexus and Pixel Devices It often provides more detailed information about the boot process and slot statusAndroid fastboot 查詢當使用的a/b槽
* `update_engine`: This is the system service responsible for handling OTA updates on devices with A/B partitionsInstallation | KernelSU It interacts with the bootloader and manages the slot switching logicThis page contains answers to frequently asked questions aboutGrapheneOS. It's not an overview of the project or a list of interesting topics about GrapheneOS.
* `fastbootd`: This is a user-space fastboot implementation that can be useful for flashing partitions that cannot be accessed in the traditional bootloader fastboot modeFactory Images for Nexus and Pixel Devices
Conclusion
Mastering the fastboot get active slot command and understanding the underlying A/B partitioning scheme is an essential skill for anyone engaging with Android's system-level operations[Recovery] Switch slots on A/B device r/LineageOS By correctly querying, setting, and managing your active slots, you can ensure smoother updates, more efficient troubleshooting, and a more robust Android experienceGrapheneOS Frequently Asked Questions Remember to always proceed with caution when using fastboot commands, as incorrect usage can potentially lead to device instabilityThis page contains answers to frequently asked questions aboutGrapheneOS. It's not an overview of the project or a list of interesting topics about GrapheneOS. Verifying the active slot before and after critical operations is a small step that can prevent significant issuesThis page contains binary image files that allow you to restore your Nexus or Pixel device's original factory firmware.