How to Add Delay at Boot

Question

Running Raspbian on RPi 2B:

Perhaps foolishly I've chosen the RPi for a significant development that needs much more than its internal flash storage, so have attached a terabyte USB drive as sda1. During power-on boot the following is reported:

[10.872768] sd 0:0:0:0 [sda] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB) / failed

This is despite the following line having been inserted to /etc/fstab:

/dev/sda1 /mnt auto defaults,exec 0 2

Thereafter the drive cannot be accessed except by performing a commanded mount. Or a reboot. Obviously the problem occurs because the Western Digital "Bookcase" drive becomes operational from power-on slower than the RPi. A few seconds "sleep" added to the boot process almost anywhere before that failure would synchronize the two.

The question is, where and how to issue the sleep? Progress through the Raspbian boot sequence scripts in /etc is not at all clear.

Answer 1

There are two entries you can add to /boot/config.txt to delay boot.

boot_delay=x
Wait for x seconds in start.elf before loading kernel.
Default 1.

boot_delay_ms=x
Wait for x milliseconds in start.elf before loading kernel.
Default 0.

Boot delay = 1000 * boot_delay + boot_delay_ms.

See http://elinux.org/RPiconfig#Boot

Answer 2

To my knowledge, there's no way in which you can put a sleep mode in your fstab entry. If it's not possible to leave the RPi on all the time, I would mount the drive using the root user's crontab and the @reboot flag.

The key part you'll need is bash's sleep command.

Steps:

1. sudo crontab -e
2. add the line @reboot sleep {time in seconds} ; {mount cmd here}
3. save
4. exit
5. test it

Warning: Do not try to use a sleep call in an init script. Init scripts are processed sequentially, and if you sleep in one, all others will wait until that one finishes.

Answer 3

I think what you're looking for is a way to automatically mount a USB drive, see if usbmount works for you. Installation is:

sudo apt-get install -y usbmount

For more info, check out this answer.

Answer 4

I had the same problem. I wrote a quick and dirty "delay" (5 seconds) program in C. I called the program in rc.local, then ran mount -a (mount -a re-runs fstab) on the next line of rc.local. this allowed time for my hdd to spin up on my raspberry minidlna server.