MicroSD Card not visible on boot in linux
Table of Contents
I’m still using my chromebook with coreboot as a portable thinclient. Due to small built-in storage (only 16GB), i’m also using microSD card as a secondary storage for larger files and project. However i was strugeling with microSD card not being mounted at boot (waiting for device), my solution was to just physically eject and insert the card at boot, but it is pretty inconvient and is probably destroying the card pins.
The solution⌗
The solution was to create a systemd unit, that will run on boot before local-fs.target
# /etc/systemd/system/rescan-sd-card.service
[Unit]
Description=Remove and rescan MMC and PCI devices before mounting filesystems
DefaultDependencies=no
Before=local-fs.target
[Service]
Type=oneshot
ExecStart=/bin/sh -c 'echo 1 > /sys/class/mmc_host/mmc0/device/remove'
ExecStartPost=/bin/sh -c 'echo 1 > /sys/class/pci_bus/0000:00/rescan'
RemainAfterExit=yes
[Install]
WantedBy=local-fs.target
Note: check if on your device the sdcard is also mmc0 - you can check it just by looking at lsblk.
After creating the file at /etc/systemd/system/rescan-sd-card.service, we need to enable it
sudo systemctl enable rescan-sd-card.service
And now, on boot, the system will ‘remove’ the mmc device, and rescan pci bus. That solved the issue and now my OS is booting without user intervention.