CODEWITHSUNDEEP
embedded-linuxsystemd
sibrown
sibrown

Reputation: 35

Embedded linux application start script works better from command line

I'm running embedded linux on an Altera FPGA. It uses SystemD to run startup, and I have a script in the "multi-user.target.wants" section that runs my application.

When it runs from startup my code runs slower than when I run the identical script from an ssh shell.

I have checked that paths are the same, that permissions are correct on the scripts, that full paths are used in the scripts. Using 'top' I can see that priorities are set the same for the various threads started, yet somehow performance is completely different between the two ways of starting.

The script in full is:

#!/bin/sh
sleep 5s
mount /dev/mmcblk0p5 /home/root/linux
cd /home/root/linux/mem_driver
./memdev_load
cd /home/root/linux/gpio_driver
insmod ./gpiodev.ko
mknod /dev/gpiodev c 249 0
sleep 5s
cd /home/root/src/control
mysqld_safe &
up=0
while [ $up -ne 2 ] 
do
    up=$(pgrep mysql | wc -l);
    echo $up
done
sleep 3s
cd /home/root/studio_web/myapp
npm start &
sleep 1s
cd /home/root/src/control
#sleep 1s
./control > /home/root/linux/output.log

various sleep commands have been inserted to try and make sure things start up in the right order.

Any help in diagnosing why this behaves differently would be greatly appreciated.

Upvotes: 1

Views: 1036

Answers (1)

Brendan
Brendan

Reputation: 978

Is that the only shell script you are using? or do you have a systemd service file that executes that single shell script?

Using sleep is ineffective here. You should separate them into separate shell scripts and then use systemd to ensure that the shell scripts are run in order.

For example, we want to mount the directory first, because if this fails then nothing following will be successful. So we create a systemd mount service:

# home-root-linux.mount
[Unit] 
Description=Mount /home/root/linux
Before=gpiodev.service

[Mount]
What=/dev/mmcblk0p5 
Where=/home/root/linux 
Options=defaults

[Install] 
WantedBy=multi-user.target

Then we can create another systemd service which depends on the mount above before executing the three parts of the shell script which were previously separated by sleep to ensure that they were run in order.

# gpiodev.service
[Unit]
Description=Handle gpiodev kernel module
After=home-root-linux.mount
Before=mysqlsafe.service

[Service]
Type=oneshot
ExecStartPre=/home/root/linux/mem_driver/memdev_load
ExecStart=/sbin/insmod gpiodev.ko; /bin/mknod /dev/gpiodev c 249 0
WorkingDirectory=/home/root/linux/gpio_driver
RemainAfterExit=yes
StandardOutput=journal

[Install]
WantedBy=multi-user.target

Second part of the systemd service (following the sleep). We have a separate shellscript which is placed in /sbin/ in this example as it contains a while loop so it would be best to separate this:

# mysqlsafe.service
[Unit]
Description=MySQL safe
After=gpiodev.service
Before=npmoutput.service

[Service]
Type=oneshot
ExecStart=/sbin/mysqlsafe.sh
WorkingDirectory=/home/root/src/control
RemainAfterExit=yes
StandardOutput=journal

[Install]
WantedBy=multi-user.target

Second part of the shell script which is executed in the systemd service above (separated to a separate file due to the complexity):

# /sbin/mysqlsafe.sh
#!/bin/sh
mysqld_safe &
up=0
while [ $up -ne 2 ] 
do
    up=$(pgrep mysql | wc -l);
    echo $up
done

Third part of the systemd service (the third section of the original shell script which was separated by sleep):

# mpmoutput.service
[Unit]
Description=npm and output to log
After=mysqlsafe.service

[Service]
Type=oneshot
ExecStartPre=/usr/bin/npm &
ExecStart=/home/root/src/control > /home/root/linux/output.log
WorkingDirectory=/home/root/studio_web/myapp
RemainAfterExit=yes
StandardOutput=journal

[Install]
WantedBy=multi-user.target

The idea behind this approach is that systemd recognises the importance of each service and the reliance upon the following service i.e. if one service fails the following services in queue will not execute. You can then check this using systemctl and see logging in journalctl.

Just a quick copy, paste and edit. Could contain errors as it was not tested or checked.

More reading can be found here regarding systemd service files: https://www.freedesktop.org/software/systemd/man/systemd.service.html

Upvotes: 0

Related Questions