How to Boot from NVMe SSD?

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
,
16

Hi,
I have modified furushchev’s solution in “true” systemd way and become able to mount SSD drive as rootfs without overlay and reboot problems.

  1. Xavier was flashed and software was installed using SDKManager.
  2. Rootfs from eMMC was copied to SSD ( with one ext4 partition in my case): 
    #!/bin/bash
sudo mount /dev/nvme0n1p1 /mnt
sudo rsync -aAXv / --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found"} /mnt
  3. Then we need systemd unit, loading just after unmounting initrd image and mounting real rootfs, before any other targets running with systemd from real rootfs. Something like following: setssdroot.service: 
    [Unit]
Description=Change rootfs to SSD in M.2 key M slot (nvme0n1p1)
DefaultDependencies=no
Conflicts=shutdown.target
After=systemd-remount-fs.service
Before=local-fs-pre.target local-fs.target shutdown.target
Wants=local-fs-pre.target
ConditionPathExists=/dev/nvme0n1p1
ConditionVirtualization=!container

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/sbin/setssdroot.sh

[Install]
WantedBy=default.target

    I added condition to start only if SSD is installed ( /dev/nvme0n1p1 exists).

    setssdroot.sh:

    #!/bin/sh
NVME_DRIVE="/dev/nvme0n1p1"
CHROOT_PATH="/nvmeroot"

INITBIN=/lib/systemd/systemd
EXT4_OPT="-o defaults -o errors=remount-ro -o discard"

modprobe ext4
#modprobe fuse

mkdir -p ${CHROOT_PATH}
mount -t ext4 ${EXT4_OPT} ${NVME_DRIVE} ${CHROOT_PATH}

cd ${CHROOT_PATH}
/bin/systemctl --no-block switch-root ${CHROOT_PATH}
  4. New target was installed with following command: 
    #!/bin/sh
sudo cp setssdroot.service /etc/systemd/system
sudo cp setssdroot.sh /sbin
sudo chmod 777 /sbin/setssdroot.sh
systemctl daemon-reload
sudo systemctl enable setssdroot.service

As a result, after reboot systemd mounts /dev/nvme0n1p1 as “/”. We are working with system (except kernel and initrd) from SSD and have “recovery” system on eMMC.

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