# Boot Linux operating system from the SD card You can boot up Qualcomm development kits from the SD card. 1. Prepare the SD card by flashing it with `efi.bin` and `rootfs.img`. 2. Insert the prepared SD card into the SD card slot of the development kit. The development kit boots up from the SD card, which contains a backup or redundant operating system to ensure continuous operation. To boot Qualcomm development kits from an SD card, do the following: **Prerequisites** Use a Linux desktop system to perform steps 1 through 5 and prepare a bootable SD card. **Procedure** 1. Verify the device node for the inserted SD card on any Linux system, for example, `/dev/mmcblk1` or `/dev/mmcblk2`. 2. To format the SD card, run the `mkfs.ext4 ` command on the Linux terminal. In the following example, the dev node for the SD card is `/dev/mmcblk1`. mkfs.ext4 /dev/mmcblk1 Copy to clipboard Output: mke2fs 1.46.5 (30-Dec-2021) Found a dos partition table in /dev/mmcblk1 Proceed anyway? (y,N) y Discarding device blocks: done Creating filesystem with 3889536 4k blocks and 972944 inodes Filesystem UUID: 069e04f8-0b72-4a94-aa93-f5ec03bea38d Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208 Allocating group tables: done Writing inode tables: done Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: done Copy to clipboard 3. Use the `fdisk` command to create two partitions on the SD card to copy `efi.bin` and `rootfs.img`. 1. Create the first partition with the `vfat` file system to copy `efi.bin`. To create the partition, run the following command (for example, the dev node is `/dev/mmcblk1`): In this example, leave the `First sector` field empty and ensure that `Last sector` is large enough to copy `efi.bin`. fdisk /dev/mmcblk1 Copy to clipboard Output: Welcome to fdisk (util-linux 2.37.4). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. The device contains 'ext4' signature and it will be removed by a write command. See fdisk(8) man page and --wipe option for more details. Device doesn't contain a recognized partition table. Created a new DOS disklabel with disk identifier 0xa5fa6b03. Command (m for help): n Partition type p primary (0 primary, 0 extended, 4 free) e extended (container for logical partitions) Select (default p): p Partition number (1-4, default 1): 1 First sector (2048-31116287, default 2048): Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-31116287, default 31116287): +512M Created a new partition 1 of type 'Linux' and of size 512 MiB. Command (m for help): w The partition table has been altered. Calling ioctl() to re-read partition table. Syncing disks. Copy to clipboard To convert the partition to the `vfat` file system, run the following command: mkfs.vfat /dev/mmcblk1p1 Copy to clipboard Output: mkfs.fat 4.2 (2021-01-31) Copy to clipboard 2. Create the second partition with the `ext4` file system to copy `rootfs.img` as follows: To create the partition, run the following command (for example, the dev node is `/dev/mmcblk1`): In this example, leave the `First sector` field empty and ensure that `Last sector` is large enough to copy `rootfs.img`. fdisk /dev/mmcblk1 Copy to clipboard Output: Welcome to fdisk (util-linux 2.37.4). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Command (m for help): n Partition type p primary (1 primary, 0 extended, 3 free) e extended (container for logical partitions) Select (default p): p Partition number (2-4, default 2): 2 First sector (1050624-31116287, default 1050624): Last sector, +/-sectors or +/-size{K,M,G,T,P} (1050624-31116287, default 31116287): +10G Created a new partition 2 of type 'Linux' and of size 10 GiB. Command (m for help): w The partition table has been altered. Calling ioctl() to re-read partition table. Syncing disks. Copy to clipboard To convert the partition to the `ext4` file system, run the following command: mkfs.ext4 /dev/mmcblk1p2 Copy to clipboard Output: mke2fs 1.46.5 (30-Dec-2021) Discarding device blocks: done Creating filesystem with 2621440 4k blocks and 655360 inodes Filesystem UUID: 9e470d01-77fe-4382-a273-ab8b022bdd8b Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632 Allocating group tables: done Writing inode tables: done Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: done Copy to clipboard 4. Verify the partitions were created: lsblk -f /dev/mmcblk1 Copy to clipboard Output: NAME FSTYPE FSVER LABEL UUID FSAVAIL FSUSE% MOUNTPOINTS mmcblk1 | |-mmcblk1p1 | vfat 1EAC-8FF8 `-mmcblk1p2 ext4 9e470d01-77fe-4382-a273-ab8b022bdd8b Copy to clipboard 5. Copy `efi.bin` and `rootfs.img` from the successfully built Qualcomm Linux image on the host computer to the partitions on the SD card. Run the following commands on the host computer: - `dd if=/efi.bin of= bs=4M` - `dd if=/rootfs.img of= bs=4M` To copy both images from the `/tmp` path, following is an example of how to copy them to the SD card: In this command, the dev node for the SD card is `/dev/mmcblk1`. dd if=/tmp/efi.bin of=/dev/mmcblk1p1 bs=4M dd if=/tmp/rootfs.img of=/dev/mmcblk1p2 bs=4M Copy to clipboard Note The `efi.bin` and `rootfs.img` images copied to the SD card must be built using either the `qcom-distro-sota` or `qcom-distro-catchall` distro configuration. **Result** The SD card is now ready to be used as boot media for a Qualcomm Linux development kit. When an SD card is inserted, it is used as fallback boot media only if the primary flash storage (UFS or eMMC) on the development kit is unbootable. To simulate an unbootable condition, erase the EFI partition on the UFS or eMMC storage to force a fallback boot from the SD card. Last Published: May 10, 2026 [Previous Topic Update firmware and OS on Qualcomm Linux using capsule and OSTree mechanisms](https://docs.qualcomm.com/bundle/publicresource/80-80022-27/topics/update_fw_and_os_qualcomm_linux_using_capsule_and_ostree_mechanisms.md) [Next Topic Manage UEFI environment variables using the efivar tool](https://docs.qualcomm.com/bundle/publicresource/80-80022-27/topics/manage_uefi_environment_variables_using_efivar_tool.md)