6 Software
User Manual 78/374
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To activate the overlay filesystem, add the parameter "overlay_on" to the U-Boot bootargs:
setenv ubifsargs setenv bootargs console=ttyPSC3,115200 ubi.mtd=0 root=ubi0:rootfs rw
rootfstype=ubifs quiet overlay_on
After saving the U-Boot variables and booting the TC1 the overlay feature can be used.
Activate the overlay filesystem in the user space
To activate the overlay filesystem, add the parameter "overlay_on" to the user space:
fw_setenv ubifsargs setenv bootargs console=ttyPSC3,115200 ubi.mtd=0 root=ubi0:rootfs rw
rootfstype=ubifs quiet overlay_on
After restarting the TC1 the overlay feature can be used.
Examples
Example1:
If the user changes the /etc/init.d/rc.conf file, the changes will be stored to
/mnt/dataflash/stw/overlay/etc/init.d/rc.conf.
The original root filesystem remains unchanged.
If the user deletes the /mnt/dataflash/stw/overlay/etc/init.d/rc.conf file, the original /etc/init.d/rc.conf file from the
rootfs will be restored.
Example2:
If the user deletes the /etc/init.d/scripts/bt script in the root filesystem, then the TC1 behaves like the file is
gone. But the file is not really deleted. Only a flag in the corresponding overlay directory is set. In this case the
flag is set in the /mnt/dataflash/stw/overlay/etc/init.d/script directory.
# ls -al /mnt/dataflash/stw/overlay/etc/init.d/scripts/
total 3
drwxrwxr-x 2 root root 288 Nov 24 15:57 .
drwxrwxr-x 3 root root 360 Nov 19 15:41 ..
---------- 1 root root 0 Nov 24 15:57 .wh.bt
After removing the flag or deactivating the overlay, the file is restored in the root filesystem.
6.5.2 NAND Flash
The NAND flash is mounted to the path /mnt/dataflash.
It is recommended to store all the user data to /mnt/dataflash to avoid data loss.
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