Enabling systemd service with preseed - linux

I'm trying to enable serial-getty#ttyS0.service to output getty to serial console as well as tty0.
I have tried running systemctl enable serial-getty#ttyS0 but I suspect that systemd might not be running when late_command is running.
Then I tried making the symlink manually with ln -s /lib/systemd/system/serial-getty#.service /etc/systemd/system/getty.target.wants/serial-getty#ttyS0.service and after the install getty.target.wants only contains getty#tty1.service.
I can't use console=tty0 console=ttyS0,115200n8 kernel parameter because then messages from the init system and the system logger will only appear on the first serial port and I want them to appear on tty0.
Does anyone have any experience or any idea on how to enable services in preseed config?
Thanks.

Related

program running a boot on BeagleBoneblack

I am having a problem with a small application I developed on the BBB running Debian Image 2017-03-19.
I connected a barcode scanner to the usb port and a 2x16 LCD display to the GPIO controlled by BBBioLib.
I developed an application in C to read a barcode label apply to a race tyre, which find a match on an SQLite table and show the racer name on the display.
Application work great but since the all assembly must work stand alone I need to run the program automatically at boot.
I follow all the instruction on creating a bash program and service but I am getting a strange behaviour.
The display after the welcome message hang up and never change but the application work correctly because all the printf to the consolle get logged correctly and once I exit the application I can check them on the log of the service.
If I restart the service manually everything work fine.
This is the bash script
#!/bin/bash
/root/read_barcode
This is the service code
[Unit]
Description=Barcode reader launch
After=syslog.target network.target
[Service]
Type=simple
ExecStart=/usr/bin/barcode.sh
[Install]
WantedBy=multi-user.target
Does anyone can help on solving this problem.
Thanks
Carlo
Run a .service file with sudo systemctl enable YourService.service at this location.
/etc/systemd/system/
Use the enable option for systemd .service files to make your source work on boot or a reboot.

Systemd service failing on startup

I'm trying to get a nodejs server to run on startup, so I created the following systemd unit file:
[Unit]
Description=TI SensorTag Communicator
After=network.target
[Service]
ExecStart=/usr/bin/node /home/pi/sensortag-comm/sensortag.js
User=root
[Install]
WantedBy=multi-user.target
I'm not sure what I'm doing wrong here. It seems to fail before the nodejs script even starts, as no logging occurs. My script is dependent on mysql 5.5 (I think this is where I'm running into an issue). Any insight, or even a different solution would be appreciated.
Also, it runs fine once I'm logged into the system.
Update
The service is enabled, and is logging through journalctl. I'll update with the results on 7/11/16.
Not sure why it didn't work the first time, but upon checking journalctl the issue was 100% that MySQL hadn't started. I once again changed it to After=MySQL.service and it worked perfectly!
If there is no mention of the service at all in the output of journalctl that could indicate that the service was not enabled to start at boot.
Make you run systemctl enable my-unit-name before your next boot test.
Also, since you depend on MySQL being up and running, you should declare that with something like: After=mysql.service. The exact service name may depend on your Linux distribution, which you didn't state.
Adding User=root adds nothing, as system units would be run by root by default anyway.
When you said "it fails", you didn't specify whether it was failing at boot time, or with a test run by systemctl start my-unit-name.
After attempting to start a service, there should be logging if you run journalctl -u my-unit.name.service.
You might also consider adding StandardOutput=journal to your unit file to make sure you capture output from the service you are running as well.

Run a script after Bluetooth is configured and running - Rasperry Pi 3

I'm trying to automatically call a program at boot that uses Bluetooth. However, the program is being called before Bluetooth is configured and running.
I've tried calling the program in two ways:
Using a script in init.d and registered with update-rc.d with this line in the init: # Required-Start: $all
Calling it from /etc/rc.local
Neither of these work as desired. They both start the program, but before Bluetooth is configured and running.
What is the best way to force a script or program to run after Bluetooth?
Below are some select lines from the boot sequence so you can see the issue I'm having:
[ OK ] Started Login Service.
[ OK ] Started Getty on tty1.
**Where my program is currently executing**
[ OK ] Started Configure Bluetooth Modems connected by UART.
[ OK ] Reached Target Bluetooth
**Where I want my program to be executing**
Raspbian GNU/Linux 8 tty1
login:
The new init system for Debian 8 "Jessie" is systemd. The old way in Debian 7 "Wheezy" was Sysv with runlevels and /etc/inittab. A drawback of using crontab to run your program will be, if the script execution crashes, it dies forever. Restarting a script automatically if its ends is called "respawn".
As you can see, the Bluetooth Service is running and prints that a "Target" is reached. To create your own service, which runs after bluetooth startup, and respawns with systemd just create a file in /etc/systemd/system/ i.e. my_program.service
[Unit]
Desription=my_program with systemd, respawn, after bluetooth
After=bluetooth.target
[Service]
ExecStart=node /home/pi/workspace/my_program
Restart=always
[Install]
WantedBy=multi-user.target
and activate it
systemctl enable my_program.service
reboot or start it manually
systemctl daemon-reload
systemctl start my_program.service
If one kills the process or reboots, my_program will be restarted automatically some seconds later.
For anyone running Raspbian 9 (stretch)
I tried out #andpei's answer and my application still wasn't waiting for bluetooth to start up. I was able to solve this by adding "Requires".
[Unit]
Desription=my_program with systemd, respawn, after bluetooth
After=bluetooth.target
Requires=bluetooth.target
Using crontab, I was able to make it work with the following line:
#reboot sleep 5 && node /home/pi/workspace/my_program
Not ideal but it works for now. I'm open to any better answers.

Effect of redirects on reboot command

I'm running linux on a mips based system (specifically openwrt on a router).
When I run the reboot (as supplied by busybox) i.e. just reboot on it's own, the system reboots, but some of the services (webserver, dhcp/dns, dsl stuff) don't start up.
However when I reboot via the web interface, all the services start normally. I looked at the code and saw that the web interface runs reboot > /dev/null 2>&1. Running this command also reboots and starts up0 the services properly.
My question is how does redirecting stdout and stderr to /dev/null affect the startup of services upon the next boot?
Also, I'm wondering, would reboot contain architecture specific code?
No, redirecting stdout/stderr must not be able to affect the boot process (and where would that be saved anyway?). There must be something else causing this.
Does "shutdown -r now" work?

How can I automatically start a node.js application in Amazon Linux AMI on aws?

Is there a brief guide to explain how to start up a application when the instance starts up and running? If it were one of the services installed through yum then I guess I can use /sbin/chkconfig to add it to the service. (To make it sure, is it correct?)
However, I just want to run the program which was not installed through yum. To run node.js program, I will have to run script sudo node app.js at home directory whenever the system boots up.
I am not used to Amazon Linux AMI so I am having little trouble finding a 'right' way to run some script automatically on every boot.
Is there an elegant way to do this?
One way is to create an upstart job. That way your app will start once Linux loads, will restart automatically if it crashes, and you can start / stop / restart it by sudo start yourapp / sudo stop yourapp / sudo restart yourapp.
Here are beginning steps:
1) Install upstart utility (may be pre-installed if you use a standard Amazon Linux AMI):
sudo yum install upstart
For Ubuntu:
sudo apt-get install upstart
2) Create upstart script for your node app:
in /etc/init add file yourappname.conf with the following lines of code:
#!upstart
description "your app name"
start on started mountall
stop on shutdown
# Automatically Respawn:
respawn
respawn limit 99 5
env NODE_ENV=development
# Warning: this runs node as root user, which is a security risk
# in many scenarios, but upstart-ing a process as a non-root user
# is outside the scope of this question
exec node /path_to_your_app/app.js >> /var/log/yourappname.log 2>&1
3) start your app by sudo start yourappname
You can use forever-service for provisioning node script as a service and automatically starting during boots. Following commands will do the needful,
npm install -g forever-service
forever-service install test
This will provision app.js in the current directory as a service via forever. The service will automatically restart every time system is restarted. Also when stopped it will attempt a graceful stop. This script provisions the logrotate script as well.
Github url: https://github.com/zapty/forever-service
As of now forever-service supports Amazon Linux, CentOS, Redhat support for other Linux distro, Mac and Windows are in works..
NOTE: I am the author of forever-service.
Quick solution for you would be to start your app from /etc/rc.local ; just add your command there.
But if you want to go the elegant way, you'll have to package your application in a rpm file,
have a startup script that goes in /etc/rc.d so that you can use chkconfig on your app, then install the rpm on your instance.
Maybe this or this help. (or just google for "creating rpm packages")
My Amazon Linux instance runs on Ubuntu, and I used systemd to set it up.
First you need to create a <servicename>.service file. (in my case cloudyleela.service)
sudo nano /lib/systemd/system/cloudyleela.service
Type the following in this file:
[Unit]
Description=cloudy leela
Documentation=http://documentation.domain.com
After=network.target
[Service]
Type=simple
TimeoutSec=0
User=ubuntu
ExecStart=/usr/bin/node /home/ubuntu/server.js
Restart=on-failure
[Install]
WantedBy=multi-user.target
In this application the node application is started. You will need a full path here. I configured that the application should simply restart if something goes wrong. The instances that Amazon uses have no passwords for their users by default.
Reload the file from disk, and then you can start your service. You need to enable it to make it active as a service, which automatically launches at startup.
ubuntu#ip-172-31-21-195:~$ sudo systemctl daemon-reload
ubuntu#ip-172-31-21-195:~$ sudo systemctl start cloudyleela
ubuntu#ip-172-31-21-195:~$ sudo systemctl enable cloudyleela
Created symlink /etc/systemd/system/multi-user.target.wants/cloudyleela.service → /lib/systemd/system/cloudyleela.service.
ubuntu#ip-172-31-21-195:~$
A great systemd for node.js tutorial is available here.
If you run a webserver:
You probably will have some issues running your webserver on port 80. And the easiest solution, is actually to run your webserver on a different port (e.g. 4200) and then to redirect that port to port 80. You can accomplish this with the following command:
sudo iptables -t nat -A PREROUTING -i -p tcp --dport 80 -j REDIRECT --to-port 4200
Unfortunately, this is not persistent, so you have to repeat it whenever your server restarts. A better approach is to also include this command in our service script:
ExecStartPre to add the port forwarding
ExecStopPost to remove the port forwarding
PermissionStartOnly to do this with sudo power
So, something like this:
[Service]
...
PermissionsStartOnly=true
ExecStartPre=/sbin/iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 4200
ExecStopPost=/sbin/iptables -t nat -D PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 4200
Don't forget to reload and restart your service:
[ec2-user#ip-172-31-39-212 system]$ sudo systemctl daemon-reload
[ec2-user#ip-172-31-39-212 system]$ sudo systemctl stop cloudyleela
[ec2-user#ip-172-31-39-212 system]$ sudo systemctl start cloudyleela
[ec2-user#ip-172-31-39-212 system]$
For microservices (update on Dec 2020)
The previously mentioned solution gives a lot of flexibility, but it does take some time to set it up. And for each additional application, you need to go through this entire process again. By the time you'll be installing your 5th node application, you'll certainly start wondering: "there has to be a shortcut".
The advantage of PM2 is that it's just 1 service to install. Next it's PM2 which manages the actual applications.
Even the initial setup of PM2 is easy, because it automatically installs the pm2 service for you.
npm install pm2 -g
And adding new services is even easier:
pm2 start index.js --name "foo"`.
When everything's up and running, you can save your setup, to have it automatically start on reboot.
pm2 save
If you want an overview of all your running node applications,
you can run pm2 list
And PM2 also offers an online (webbased) dashboard to monitor your application remotely. You may need a license to access some of the dashboard functionality though (which is a bit over-priced imho).
You can create a script that can start and stop your app and place it in /etc/init.d; make the script adhere to chkconfig's conventions (below), and then use chkconfig to set it to start when other services are started.
You can pick an existing script from /etc/init.d to use as an example; this article describes the requirements, which are basically:
An executable script that identifies the shell needed (i.e., #!/bin/bash)
A comment of the form # chkconfig: where is often 345, startprio indicates where in the order of services to start, and stopprio is where in the order of services to stop. I generally pick a similar service that already exists and use that as a guide for these values (i.e., if you have a web-related service, start at the same levels as httpd, with similar start and stop priorities).
Once your script is set up, you can use
chkconfig --add yourscript
chkconfig yourscript on
and you should be good to go. (Some distros may require you to manually symlink to the script to /etc/init.d/rc.d, but I believe your AWS distro will do that for you when you enable the script.
Use Elastic Beanstalk :) Provides support for auto-scaling, SSL termination, blue/green deployments, etc
If you want the salty sysadmin way for a RedHat based linux distro (Amazon Linux is a flavor of RedHat), learn systemd, as mentioned by #bvdb in the answer above:
https://en.wikipedia.org/wiki/Systemd
Set everything up as described on an EC2 instance, snapshot a custom AMI, and use this custom AMI as your base for EC2 instances hosting your apps. This way you don't have to go through all that setup multiple times. You'll probably want to get acquainted with load balancers too, if you are running in a production environment with uptime requirements.
Or, yes, as mentioned by #bvdb, you could also use pm2 to interface with systemd. Though I don't think pm2 helps with running your app across multiple EC2 instances, which is definitely recommended for production environments with uptime requirements.
All of which is a very steep learning curve. Since the OP seemed to be new to all this, Elastic Beanstalk, Google App Engine, and others are a great way to get code running in the cloud without all that.
These days I dev in TypeScript, deploying to serverless function execution in the cloud for most things, and don't have to think about package installs or app startup at all.
You can use screen. Run crontab -e and add this line:
#reboot screen -d -m bash -c "cd /home/user/yourapp/; node app"
Have been using forever on AWS and it does a good job. Install using
[sudo] npm install forever -g
To add an application use
forever start path_to_application
and to stop the application use
forever stop path_to_application
This is a useful article that helped me with setting it up.

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