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I am trying to run a cronjob inside a docker container that invokes a shell script.
Yesterday I have been searching all over the web and stack overflow, but I could not really find a solution that works.
How can I do this?
You can copy your crontab into an image, in order for the container launched from said image to run the job.
Important: as noted in docker-cron issue 3: use LF, not CRLF for your cron file.
See "Run a cron job with Docker" from Julien Boulay in his Ekito/docker-cron:
Let’s create a new file called "hello-cron" to describe our job.
# must be ended with a new line "LF" (Unix) and not "CRLF" (Windows)
* * * * * echo "Hello world" >> /var/log/cron.log 2>&1
# An empty line is required at the end of this file for a valid cron file.
If you are wondering what is 2>&1, Ayman Hourieh explains.
The following Dockerfile describes all the steps to build your image
FROM ubuntu:latest
MAINTAINER docker#ekito.fr
RUN apt-get update && apt-get -y install cron
# Copy hello-cron file to the cron.d directory
COPY hello-cron /etc/cron.d/hello-cron
# Give execution rights on the cron job
RUN chmod 0644 /etc/cron.d/hello-cron
# Apply cron job
RUN crontab /etc/cron.d/hello-cron
# Create the log file to be able to run tail
RUN touch /var/log/cron.log
# Run the command on container startup
CMD cron && tail -f /var/log/cron.log
But: if cron dies, the container keeps running.
(see Gaafar's comment and How do I make apt-get install less noisy?:
apt-get -y install -qq --force-yes cron can work too)
As noted by Nathan Lloyd in the comments:
Quick note about a gotcha:
If you're adding a script file and telling cron to run it, remember to
RUN chmod 0744 /the_script
Cron fails silently if you forget.
OR, make sure your job itself redirect directly to stdout/stderr instead of a log file, as described in hugoShaka's answer:
* * * * * root echo hello > /proc/1/fd/1 2>/proc/1/fd/2
Replace the last Dockerfile line with
CMD ["cron", "-f"]
But: it doesn't work if you want to run tasks as a non-root.
See also (about cron -f, which is to say cron "foreground") "docker ubuntu cron -f is not working"
Build and run it:
sudo docker build --rm -t ekito/cron-example .
sudo docker run -t -i ekito/cron-example
Be patient, wait for 2 minutes and your command-line should display:
Hello world
Hello world
Eric adds in the comments:
Do note that tail may not display the correct file if it is created during image build.
If that is the case, you need to create or touch the file during container runtime in order for tail to pick up the correct file.
See "Output of tail -f at the end of a docker CMD is not showing".
See more in "Running Cron in Docker" (Apr. 2021) from Jason Kulatunga, as he commented below
See Jason's image AnalogJ/docker-cron based on:
Dockerfile installing cronie/crond, depending on distribution.
an entrypoint initializing /etc/environment and then calling
cron -f -l 2
The accepted answer may be dangerous in a production environment.
In docker you should only execute one process per container because if you don't, the process that forked and went background is not monitored and may stop without you knowing it.
When you use CMD cron && tail -f /var/log/cron.log the cron process basically fork in order to execute cron in background, the main process exits and let you execute tailf in foreground. The background cron process could stop or fail you won't notice, your container will still run silently and your orchestration tool will not restart it.
You can avoid such a thing by redirecting directly the cron's commands output into your docker stdout and stderr which are located respectively in /proc/1/fd/1 and /proc/1/fd/2.
Using basic shell redirects you may want to do something like this :
* * * * * root echo hello > /proc/1/fd/1 2>/proc/1/fd/2
And your CMD will be : CMD ["cron", "-f"]
But: this doesn't work if you want to run tasks as a non-root.
For those who wants to use a simple and lightweight image:
FROM alpine:3.6
# copy crontabs for root user
COPY config/cronjobs /etc/crontabs/root
# start crond with log level 8 in foreground, output to stderr
CMD ["crond", "-f", "-d", "8"]
Where cronjobs is the file that contains your cronjobs, in this form:
* * * * * echo "hello stackoverflow" >> /test_file 2>&1
# remember to end this file with an empty new line
But apparently you won't see hello stackoverflow in docker logs.
What #VonC has suggested is nice but I prefer doing all cron job configuration in one line. This would avoid cross platform issues like cronjob location and you don't need a separate cron file.
FROM ubuntu:latest
# Install cron
RUN apt-get -y install cron
# Create the log file to be able to run tail
RUN touch /var/log/cron.log
# Setup cron job
RUN (crontab -l ; echo "* * * * * echo "Hello world" >> /var/log/cron.log") | crontab
# Run the command on container startup
CMD cron && tail -f /var/log/cron.log
After running your docker container, you can make sure if cron service is working by:
# To check if the job is scheduled
docker exec -ti <your-container-id> bash -c "crontab -l"
# To check if the cron service is running
docker exec -ti <your-container-id> bash -c "pgrep cron"
If you prefer to have ENTRYPOINT instead of CMD, then you can substitute the CMD above with
ENTRYPOINT cron start && tail -f /var/log/cron.log
But: if cron dies, the container keeps running.
There is another way to do it, is to use Tasker, a task runner that has cron (a scheduler) support.
Why ? Sometimes to run a cron job, you have to mix, your base image (python, java, nodejs, ruby) with the crond. That means another image to maintain. Tasker avoid that by decoupling the crond and you container. You can just focus on the image that you want to execute your commands, and configure Tasker to use it.
Here an docker-compose.yml file, that will run some tasks for you
version: "2"
services:
tasker:
image: strm/tasker
volumes:
- "/var/run/docker.sock:/var/run/docker.sock"
environment:
configuration: |
logging:
level:
ROOT: WARN
org.springframework.web: WARN
sh.strm: DEBUG
schedule:
- every: minute
task: hello
- every: minute
task: helloFromPython
- every: minute
task: helloFromNode
tasks:
docker:
- name: hello
image: debian:jessie
script:
- echo Hello world from Tasker
- name: helloFromPython
image: python:3-slim
script:
- python -c 'print("Hello world from python")'
- name: helloFromNode
image: node:8
script:
- node -e 'console.log("Hello from node")'
There are 3 tasks there, all of them will run every minute (every: minute), and each of them will execute the script code, inside the image defined in image section.
Just run docker-compose up, and see it working. Here is the Tasker repo with the full documentation:
http://github.com/opsxcq/tasker
Though this aims to run jobs beside a running process in a container via Docker's exec interface, this may be of interest for you.
I've written a daemon that observes containers and schedules jobs, defined in their metadata, on them. Example:
version: '2'
services:
wordpress:
image: wordpress
mysql:
image: mariadb
volumes:
- ./database_dumps:/dumps
labels:
deck-chores.dump.command: sh -c "mysqldump --all-databases > /dumps/dump-$$(date -Idate)"
deck-chores.dump.interval: daily
'Classic', cron-like configuration is also possible.
Here are the docs, here's the image repository.
VonC's answer is pretty thorough. In addition I'd like to add one thing that helped me. If you just want to run a cron job without tailing a file, you'd be tempted to just remove the && tail -f /var/log/cron.log from the cron command.
However this will cause the Docker container to exit shortly after running because when the cron command completes, Docker thinks the last command has exited and hence kills the container. This can be avoided by running cron in the foreground via cron -f.
If you're using docker for windows, remember that you have to change your line-ending format from CRLF to LF (i.e. from dos to unix) if you intend on importing your crontab file from windows to your ubuntu container. If not, your cron-job won't work. Here's a working example:
FROM ubuntu:latest
RUN apt-get update && apt-get -y install cron
RUN apt-get update && apt-get install -y dos2unix
# Add crontab file (from your windows host) to the cron directory
ADD cron/hello-cron /etc/cron.d/hello-cron
# Change line ending format to LF
RUN dos2unix /etc/cron.d/hello-cron
# Give execution rights on the cron job
RUN chmod 0644 /etc/cron.d/hello-cron
# Apply cron job
RUN crontab /etc/cron.d/hello-cron
# Create the log file to be able to run tail
RUN touch /var/log/hello-cron.log
# Run the command on container startup
CMD cron && tail -f /var/log/hello-cron.log
This actually took me hours to figure out, as debugging cron jobs in docker containers is a tedious task. Hope it helps anyone else out there that can't get their code to work!
But: if cron dies, the container keeps running.
I created a Docker image based on the other answers, which can be used like
docker run -v "/path/to/cron:/etc/cron.d/crontab" gaafar/cron
where /path/to/cron: absolute path to crontab file, or you can use it as a base in a Dockerfile:
FROM gaafar/cron
# COPY crontab file in the cron directory
COPY crontab /etc/cron.d/crontab
# Add your commands here
For reference, the image is here.
Unfortunately, none of the above answers worked for me, although all answers lead to the solution and eventually to my solution, here is the snippet if it helps someone. Thanks
This can be solved with the bash file, due to the layered architecture of the Docker, cron service doesn't get initiated with RUN/CMD/ENTRYPOINT commands.
Simply add a bash file which will initiate the cron and other services (if required)
DockerFile
FROM gradle:6.5.1-jdk11 AS build
# apt
RUN apt-get update
RUN apt-get -y install cron
# Setup cron to run every minute to print (you can add/update your cron here)
RUN touch /var/log/cron-1.log
RUN (crontab -l ; echo "* * * * * echo testing cron.... >> /var/log/cron-1.log 2>&1") | crontab
# entrypoint.sh
RUN chmod +x entrypoint.sh
CMD ["bash","entrypoint.sh"]
entrypoint.sh
#!/bin/sh
service cron start & tail -f /var/log/cron-2.log
If any other service is also required to run along with cron then add that service with & in the same command, for example: /opt/wildfly/bin/standalone.sh & service cron start & tail -f /var/log/cron-2.log
Once you will get into the docker container there you can see that testing cron.... will be getting printed every minute in file: /var/log/cron-1.log
But, if cron dies, the container keeps running.
Define the cronjob in a dedicated container which runs the command via docker exec to your service.
This is higher cohesion and the running script will have access to the environment variables you have defined for your service.
#docker-compose.yml
version: "3.3"
services:
myservice:
environment:
MSG: i'm being cronjobbed, every minute!
image: alpine
container_name: myservice
command: tail -f /dev/null
cronjobber:
image: docker:edge
volumes:
- /var/run/docker.sock:/var/run/docker.sock
container_name: cronjobber
command: >
sh -c "
echo '* * * * * docker exec myservice printenv | grep MSG' > /etc/crontabs/root
&& crond -f"
I decided to use busybox, as it is one of the smallest images.
crond is executed in foreground (-f), logging is send to stderr (-d), I didn't choose to change the loglevel.
crontab file is copied to the default path: /var/spool/cron/crontabs
FROM busybox:1.33.1
# Usage: crond [-fbS] [-l N] [-d N] [-L LOGFILE] [-c DIR]
#
# -f Foreground
# -b Background (default)
# -S Log to syslog (default)
# -l N Set log level. Most verbose 0, default 8
# -d N Set log level, log to stderr
# -L FILE Log to FILE
# -c DIR Cron dir. Default:/var/spool/cron/crontabs
COPY crontab /var/spool/cron/crontabs/root
CMD [ "crond", "-f", "-d" ]
But output of the tasks apparently can't be seen in docker logs.
When you deploy your container on another host, just note that it won't start any processes automatically. You need to make sure that 'cron' service is running inside your container.
In our case, I am using Supervisord with other services to start cron service.
[program:misc]
command=/etc/init.d/cron restart
user=root
autostart=true
autorestart=true
stderr_logfile=/var/log/misc-cron.err.log
stdout_logfile=/var/log/misc-cron.out.log
priority=998
From above examples I created this combination:
Alpine Image & Edit Using Crontab in Nano (I hate vi)
FROM alpine
RUN apk update
RUN apk add curl nano
ENV EDITOR=/usr/bin/nano
# start crond with log level 8 in foreground, output to stderr
CMD ["crond", "-f", "-d", "8"]
# Shell Access
# docker exec -it <CONTAINERID> /bin/sh
# Example Cron Entry
# crontab -e
# * * * * * echo hello > /proc/1/fd/1 2>/proc/1/fd/2
# DATE/TIME WILL BE IN UTC
Setup a cron in parallel to a one-time job
Create a script file, say run.sh, with the job that is supposed to run periodically.
#!/bin/bash
timestamp=`date +%Y/%m/%d-%H:%M:%S`
echo "System path is $PATH at $timestamp"
Save and exit.
Use Entrypoint instead of CMD
f you have multiple jobs to kick in during docker containerization, use the entrypoint file to run them all.
Entrypoint file is a script file that comes into action when a docker run command is issued. So, all the steps that we want to run can be put in this script file.
For instance, we have 2 jobs to run:
Run once job: echo “Docker container has been started”
Run periodic job: run.sh
Create entrypoint.sh
#!/bin/bash
# Start the run once job.
echo "Docker container has been started"
# Setup a cron schedule
echo "* * * * * /run.sh >> /var/log/cron.log 2>&1
# This extra line makes it a valid cron" > scheduler.txt
crontab scheduler.txt
cron -f
Let’s understand the crontab that has been set up in the file
* * * * *: Cron schedule; the job must run every minute. You can update the schedule based on your requirement.
/run.sh: The path to the script file which is to be run periodically
/var/log/cron.log: The filename to save the output of the scheduled cron job.
2>&1: The error logs(if any) also will be redirected to the same output file used above.
Note: Do not forget to add an extra new line, as it makes it a valid cron.
Scheduler.txt: the complete cron setup will be redirected to a file.
Using System/User specific environment variables in cron
My actual cron job was expecting most of the arguments as the environment variables passed to the docker run command. But, with bash, I was not able to use any of the environment variables that belongs to the system or the docker container.
Then, this came up as a walkaround to this problem:
Add the following line in the entrypoint.sh
declare -p | grep -Ev 'BASHOPTS|BASH_VERSINFO|EUID|PPID|SHELLOPTS|UID' > /container.env
Update the cron setup and specify-
SHELL=/bin/bash
BASH_ENV=/container.env
At last, your entrypoint.sh should look like
#!/bin/bash
# Start the run once job.
echo "Docker container has been started"
declare -p | grep -Ev 'BASHOPTS|BASH_VERSINFO|EUID|PPID|SHELLOPTS|UID' > /container.env
# Setup a cron schedule
echo "SHELL=/bin/bash
BASH_ENV=/container.env
* * * * * /run.sh >> /var/log/cron.log 2>&1
# This extra line makes it a valid cron" > scheduler.txt
crontab scheduler.txt
cron -f
Last but not the least: Create a Dockerfile
FROM ubuntu:16.04
MAINTAINER Himanshu Gupta
# Install cron
RUN apt-get update && apt-get install -y cron
# Add files
ADD run.sh /run.sh
ADD entrypoint.sh /entrypoint.sh
RUN chmod +x /run.sh /entrypoint.sh
ENTRYPOINT /entrypoint.sh
That’s it. Build and run the Docker image!
Here's my docker-compose based solution:
cron:
image: alpine:3.10
command: crond -f -d 8
depends_on:
- servicename
volumes:
- './conf/cron:/etc/crontabs/root:z'
restart: unless-stopped
the lines with cron entries are on the ./conf/cron file.
Note: this won't run commands that aren't in the alpine image.
Also, output of the tasks apparently won't appear in docker logs.
This question have a lot of answers, but some are complicated and another has some drawbacks. I try to explain the problems and try to deliver a solution.
cron-entrypoint.sh:
#!/bin/bash
# copy machine environment variables to cron environment
printenv | cat - /etc/crontab > temp && mv temp /etc/crontab
## validate cron file
crontab /etc/crontab
# cron service with SIGTERM support
service cron start
trap "service cron stop; exit" SIGINT SIGTERM
# just dump your logs to std output
tail -f \
/app/storage/logs/laravel.log \
/var/log/cron.log \
& wait $!
Problems solved
environment variables are not available on cron environment (like env vars or kubernetes secrets)
stop when crontab file is not valid
stop gracefully cron jobs when machine receive an SIGTERM signal
For context, I use previous script on Kubernetes with Laravel app.
this line was the one that helped me run my pre-scheduled task.
ADD mycron/root /etc/cron.d/root
RUN chmod 0644 /etc/cron.d/root
RUN crontab /etc/cron.d/root
RUN touch /var/log/cron.log
CMD ( cron -f -l 8 & ) && apache2-foreground # <-- run cron
--> My project run inside: FROM php:7.2-apache
But: if cron dies, the container keeps running.
When running on some trimmed down images that restrict root access, I had to add my user to the sudoers and run as sudo cron
FROM node:8.6.0
RUN apt-get update && apt-get install -y cron sudo
COPY crontab /etc/cron.d/my-cron
RUN chmod 0644 /etc/cron.d/my-cron
RUN touch /var/log/cron.log
# Allow node user to start cron daemon with sudo
RUN echo 'node ALL=NOPASSWD: /usr/sbin/cron' >>/etc/sudoers
ENTRYPOINT sudo cron && tail -f /var/log/cron.log
Maybe that helps someone
But: if cron dies, the container keeps running.
So, my problem was the same. The fix was to change the command section in the docker-compose.yml.
From
command: crontab /etc/crontab && tail -f /etc/crontab
To
command: crontab /etc/crontab
command: tail -f /etc/crontab
The problem was the '&&' between the commands. After deleting this, it was all fine.
Focusing on gracefully stopping the cronjobs when receiving SIGTERM or SIGQUIT signals (e.g. when running docker stop).
That's not too easy. By default, the cron process just got killed without paying attention to running cronjobs. I'm elaborating on pablorsk's answer:
Dockerfile:
FROM ubuntu:latest
RUN apt-get update \
&& apt-get -y install cron procps \
&& rm -rf /var/lib/apt/lists/*
# Copy cronjobs file to the cron.d directory
COPY cronjobs /etc/cron.d/cronjobs
# Give execution rights on the cron job
RUN chmod 0644 /etc/cron.d/cronjobs
# similarly prepare the default cronjob scripts
COPY run_cronjob.sh /root/run_cronjob.sh
RUN chmod +x /root/run_cronjob.sh
COPY run_cronjob_without_log.sh /root/run_cronjob_without_log.sh
RUN chmod +x /root/run_cronjob_without_log.sh
# Apply cron job
RUN crontab /etc/cron.d/cronjobs
# to gain access to environment variables, we need this additional entrypoint script
COPY entrypoint.sh /entrypoint.sh
RUN chmod +x /entrypoint.sh
# optionally, change received signal from SIGTERM TO SIGQUIT
#STOPSIGNAL SIGQUIT
# Run the command on container startup
ENTRYPOINT ["/entrypoint.sh"]
entrypoint.sh:
#!/bin/bash
# make global environment variables available within crond, too
printenv | grep -v "no_proxy" >> /etc/environment
# SIGQUIT/SIGTERM-handler
term_handler() {
echo 'stopping cron'
service cron stop
echo 'stopped'
echo 'waiting'
x=$(($(ps u -C run_cronjob.sh | wc -l)-1))
xold=0
while [ "$x" -gt 0 ]
do
if [ "$x" != "$xold" ]; then
echo "Waiting for $x running cronjob(s):"
ps u -C run_cronjob.sh
xold=$x
sleep 1
fi
x=$(($(ps u -C run_cronjob.sh | wc -l)-1))
done
echo 'done waiting'
exit 143; # 128 + 15 -- SIGTERM
}
# cron service with SIGTERM and SIGQUIT support
service cron start
trap "term_handler" QUIT TERM
# endless loop
while true
do
tail -f /dev/null & wait ${!}
done
cronjobs
* * * * * ./run_cronjob.sh cron1
*/2 * * * * ./run_cronjob.sh cron2
*/3 * * * * ./run_cronjob.sh cron3
Assuming you wrap all your cronjobs in a run_cronjob.sh script. That way, you can execute arbitrary code for which shutdown will wait gracefully.
run_cronjobs.sh (optional helper script to keep cronjob definitions clean)
#!/bin/bash
DIR_INCL="${BASH_SOURCE%/*}"
if [[ ! -d "$DIR_INCL" ]]; then DIR_INCL="$PWD"; fi
cd "$DIR_INCL"
# redirect all cronjob output to docker
./run_cronjob_without_log.sh "$#" > /proc/1/fd/1 2>/proc/1/fd/2
run_cronjob_without_log.sh
your_actual_cronjob_src()
Btw, when receiving a SIGKILL the container still shut downs immediately. That way you can use a command like docker-compose stop -t 60 cron-container to wait 60s for cronjobs to finish gracefully, but still terminate them for sure after the timeout.
All the answers require root access inside the container because 'cron' itself requests for UID 0.
To request root acces (e.g. via sudo) is against docker best practices.
I used https://github.com/gjcarneiro/yacron to manage scheduled tasks.
I occasionally tried to find a docker-friendly cron implementation. And this last time I tried, I've found a couple.
By docker-friendly I mean, "output of the tasks can be seen in docker logs w/o resorting to tricks."
The most promising I see at the moment is supercronic. It can be fed a crontab file, all while being docker-friendly. To make use of it:
docker-compose.yml:
services:
supercronic:
build: .
command: supercronic crontab
Dockerfile:
FROM alpine:3.17
RUN set -x \
&& apk add --no-cache supercronic shadow \
&& useradd -m app
USER app
COPY crontab .
crontab:
* * * * * date
A gist with a bit more info.
Another good one is yacron, but it uses YAML.
ofelia can be used, but they seem to focus on running tasks in separate containers. Which is probably not a downside, but I'm not sure why I'd want to do that.
And there's also a number of traditional cron implementations: dcron, fcron, cronie. But they come with "no easy way to see output of the tasks."
Just adding to the list of answers that you can also use this image:
https://hub.docker.com/repository/docker/cronit/simple-cron
And use it as a basis to start cron jobs, using it like this:
FROM cronit/simple-cron # Inherit from the base image
#Set up all your dependencies
COPY jobs.cron ./ # Copy your local config
Evidently, it is possible to run cron as a process inside the container (under root user) alongside other processes , using ENTRYPOINT statement in Dockerfile with start.sh script what includes line process cron start. More info here
#!/bin/bash
# copy environment variables for local use
env >> etc/environment
# start cron service
service cron start
# start other service
service other start
#...
If your image doesn't contain any daemon (so it's only the short-running script or process), you may also consider starting your cron from outside, by simply defining a LABEL with the cron information, plus the scheduler itself. This way, your default container state is "exited". If you have multiple scripts, this may result in a lower footprint on your system than having multiple parallel-running cron instances.
See: https://github.com/JaciBrunning/docker-cron-label
Example docker-compose.yaml:
version: '3.8'
# Example application of the cron image
services:
cron:
image: jaci/cron-label:latest
volumes:
- "/var/run/docker.sock:/var/run/docker.sock"
- "/etc/localtime:/etc/localtime:ro"
hello:
image: hello-world
restart: "no"
labels:
- "cron.schedule=* * * * * "
I wanted to share a modification to the typical off of some of these other suggestions that I found more flexible. I wanted to enable changing the cron time with an environment variable and ended up adding an additional script that runs within my entrypoint.sh, but before the call to cron -f
*updatecron.sh*
#!/bin/sh
#remove old cron files
rm -rf /etc/cron.*/*
#create a new formatted cron definition
echo "$crondef [appname] >/proc/1/fd/1 2>/proc/1/fd/2" >> /etc/cron.d/restart-cron
echo \ >> /etc/cron.d/restart-cron
chmod 0644 /etc/cron.d/restart-cron
crontab /etc/cron.d/restart-cron
This removes any existing cron files, creates a new cronfile using an ENV variable of crondef, and then loads it.
Our's was a nodejs application to be run as cron job and it was also dependent on environment variables.
The below solution worked for us.
Docker file:
# syntax=docker/dockerfile:1
FROM node:12.18.1
ENV NODE_ENV=production
COPY ["startup.sh", "./"]
# Removed steps to build the node js application
#--------------- Setup cron ------------------
# Install Cron
RUN apt-get update
RUN apt-get -y install cron
# Run every day at 1AM
#/proc/1/fd/1 2>/proc/1/fd/2 is used to redirect cron logs to standard output and standard error
RUN (crontab -l ; echo "0 1 * * * /usr/local/bin/node /app/dist/index.js > /proc/1/fd/1 2>/proc/1/fd/2") | crontab
#--------------- Start Cron ------------------
# Grant execution rights
RUN chmod 755 startup.sh
CMD ["./startup.sh"]
startup.sh:
!/bin/bash
echo "Copying env variables to /etc/environment so that it is available for cron jobs"
printenv >> /etc/environment
echo "Starting cron"
cron -f
With multiple jobs and various dependencies like zsh and curl, this is a good approach while also combining the best practices from other answers. Bonus: This does NOT require you to set +x execution permissions on myScript.sh, which can be easy to miss in a new environment.
cron.dockerfile
FROM ubuntu:latest
# Install dependencies
RUN apt-get update && apt-get -y install \
cron \
zsh \
curl;
# Setup multiple jobs with zsh and redirect outputs to docker logs
RUN (echo "\
* * * * * zsh -c 'echo "Hello World"' 1> /proc/1/fd/1 2>/proc/1/fd/2 \n\
* * * * * zsh /myScript.sh 1> /proc/1/fd/1 2>/proc/1/fd/2 \n\
") | crontab
# Run cron in forground, so docker knows the task is running
CMD ["cron", "-f"]
Integrate this with docker compose like so:
docker-compose.yml
services:
cron:
build:
context: .
dockerfile: ./cron.dockerfile
volumes:
- ./myScript.sh:/myScript.sh
Keep in mind that you need to docker compose build cron when you change contents of the cron.dockerfile, but changes to myScript.sh will be reflected right away as it's mounted in compose.
I have a docker container, for which I need to run the following command
php /var/www/html/artisan queue:work &
It starts a worker process that looks for jobs and executes them.
I can run it by doing exec -it when the container is running.
But I need to do it using Dockerfile so that when my container re-deploys, it starts this automatically. I have tried
RUN php /var/www/html/artisan queue:work
CMD ["php","/var/www/html/artisan","queue:work"]
ENTRYPOINT ["php","/var/www/html/artisan","queue:work"]
separately of course. but none of them work. In the case of CMD and ENTRYPOINT my container starts giving out a 502 error and my service becomes inaccessible.
What am I doing wrong?
You could do this in multiple ways.
You could write a shell script that starts the background process first and then starts your API.
CMD ["./start_server.sh"]
Contents of ./start_server.sh
#!/bin/bash
php /var/www/html/artisan queue:work &
exec php-server-serving-api
You could also do this through a docker entrypoint shell script
ENTRYPOINT ["./docker-entrypoint.sh"]
CMD ["php-server-serving-api"]
Contents of ./docker-entrypoint.sh
#!/bin/bash
php /var/www/html/artisan queue:work &
exec $#
However, what I recommend is, if they are separate type of workloads, run them in separate container. If the background processing task crashes, there is no one to restart it. If you run it as a separate container, you could use a system to restart it.
I am trying to run a cronjob inside a docker container that invokes a shell script.
Yesterday I have been searching all over the web and stack overflow, but I could not really find a solution that works.
How can I do this?
You can copy your crontab into an image, in order for the container launched from said image to run the job.
Important: as noted in docker-cron issue 3: use LF, not CRLF for your cron file.
See "Run a cron job with Docker" from Julien Boulay in his Ekito/docker-cron:
Let’s create a new file called "hello-cron" to describe our job.
# must be ended with a new line "LF" (Unix) and not "CRLF" (Windows)
* * * * * echo "Hello world" >> /var/log/cron.log 2>&1
# An empty line is required at the end of this file for a valid cron file.
If you are wondering what is 2>&1, Ayman Hourieh explains.
The following Dockerfile describes all the steps to build your image
FROM ubuntu:latest
MAINTAINER docker#ekito.fr
RUN apt-get update && apt-get -y install cron
# Copy hello-cron file to the cron.d directory
COPY hello-cron /etc/cron.d/hello-cron
# Give execution rights on the cron job
RUN chmod 0644 /etc/cron.d/hello-cron
# Apply cron job
RUN crontab /etc/cron.d/hello-cron
# Create the log file to be able to run tail
RUN touch /var/log/cron.log
# Run the command on container startup
CMD cron && tail -f /var/log/cron.log
But: if cron dies, the container keeps running.
(see Gaafar's comment and How do I make apt-get install less noisy?:
apt-get -y install -qq --force-yes cron can work too)
As noted by Nathan Lloyd in the comments:
Quick note about a gotcha:
If you're adding a script file and telling cron to run it, remember to
RUN chmod 0744 /the_script
Cron fails silently if you forget.
OR, make sure your job itself redirect directly to stdout/stderr instead of a log file, as described in hugoShaka's answer:
* * * * * root echo hello > /proc/1/fd/1 2>/proc/1/fd/2
Replace the last Dockerfile line with
CMD ["cron", "-f"]
But: it doesn't work if you want to run tasks as a non-root.
See also (about cron -f, which is to say cron "foreground") "docker ubuntu cron -f is not working"
Build and run it:
sudo docker build --rm -t ekito/cron-example .
sudo docker run -t -i ekito/cron-example
Be patient, wait for 2 minutes and your command-line should display:
Hello world
Hello world
Eric adds in the comments:
Do note that tail may not display the correct file if it is created during image build.
If that is the case, you need to create or touch the file during container runtime in order for tail to pick up the correct file.
See "Output of tail -f at the end of a docker CMD is not showing".
See more in "Running Cron in Docker" (Apr. 2021) from Jason Kulatunga, as he commented below
See Jason's image AnalogJ/docker-cron based on:
Dockerfile installing cronie/crond, depending on distribution.
an entrypoint initializing /etc/environment and then calling
cron -f -l 2
The accepted answer may be dangerous in a production environment.
In docker you should only execute one process per container because if you don't, the process that forked and went background is not monitored and may stop without you knowing it.
When you use CMD cron && tail -f /var/log/cron.log the cron process basically fork in order to execute cron in background, the main process exits and let you execute tailf in foreground. The background cron process could stop or fail you won't notice, your container will still run silently and your orchestration tool will not restart it.
You can avoid such a thing by redirecting directly the cron's commands output into your docker stdout and stderr which are located respectively in /proc/1/fd/1 and /proc/1/fd/2.
Using basic shell redirects you may want to do something like this :
* * * * * root echo hello > /proc/1/fd/1 2>/proc/1/fd/2
And your CMD will be : CMD ["cron", "-f"]
But: this doesn't work if you want to run tasks as a non-root.
For those who wants to use a simple and lightweight image:
FROM alpine:3.6
# copy crontabs for root user
COPY config/cronjobs /etc/crontabs/root
# start crond with log level 8 in foreground, output to stderr
CMD ["crond", "-f", "-d", "8"]
Where cronjobs is the file that contains your cronjobs, in this form:
* * * * * echo "hello stackoverflow" >> /test_file 2>&1
# remember to end this file with an empty new line
But apparently you won't see hello stackoverflow in docker logs.
What #VonC has suggested is nice but I prefer doing all cron job configuration in one line. This would avoid cross platform issues like cronjob location and you don't need a separate cron file.
FROM ubuntu:latest
# Install cron
RUN apt-get -y install cron
# Create the log file to be able to run tail
RUN touch /var/log/cron.log
# Setup cron job
RUN (crontab -l ; echo "* * * * * echo "Hello world" >> /var/log/cron.log") | crontab
# Run the command on container startup
CMD cron && tail -f /var/log/cron.log
After running your docker container, you can make sure if cron service is working by:
# To check if the job is scheduled
docker exec -ti <your-container-id> bash -c "crontab -l"
# To check if the cron service is running
docker exec -ti <your-container-id> bash -c "pgrep cron"
If you prefer to have ENTRYPOINT instead of CMD, then you can substitute the CMD above with
ENTRYPOINT cron start && tail -f /var/log/cron.log
But: if cron dies, the container keeps running.
There is another way to do it, is to use Tasker, a task runner that has cron (a scheduler) support.
Why ? Sometimes to run a cron job, you have to mix, your base image (python, java, nodejs, ruby) with the crond. That means another image to maintain. Tasker avoid that by decoupling the crond and you container. You can just focus on the image that you want to execute your commands, and configure Tasker to use it.
Here an docker-compose.yml file, that will run some tasks for you
version: "2"
services:
tasker:
image: strm/tasker
volumes:
- "/var/run/docker.sock:/var/run/docker.sock"
environment:
configuration: |
logging:
level:
ROOT: WARN
org.springframework.web: WARN
sh.strm: DEBUG
schedule:
- every: minute
task: hello
- every: minute
task: helloFromPython
- every: minute
task: helloFromNode
tasks:
docker:
- name: hello
image: debian:jessie
script:
- echo Hello world from Tasker
- name: helloFromPython
image: python:3-slim
script:
- python -c 'print("Hello world from python")'
- name: helloFromNode
image: node:8
script:
- node -e 'console.log("Hello from node")'
There are 3 tasks there, all of them will run every minute (every: minute), and each of them will execute the script code, inside the image defined in image section.
Just run docker-compose up, and see it working. Here is the Tasker repo with the full documentation:
http://github.com/opsxcq/tasker
Though this aims to run jobs beside a running process in a container via Docker's exec interface, this may be of interest for you.
I've written a daemon that observes containers and schedules jobs, defined in their metadata, on them. Example:
version: '2'
services:
wordpress:
image: wordpress
mysql:
image: mariadb
volumes:
- ./database_dumps:/dumps
labels:
deck-chores.dump.command: sh -c "mysqldump --all-databases > /dumps/dump-$$(date -Idate)"
deck-chores.dump.interval: daily
'Classic', cron-like configuration is also possible.
Here are the docs, here's the image repository.
VonC's answer is pretty thorough. In addition I'd like to add one thing that helped me. If you just want to run a cron job without tailing a file, you'd be tempted to just remove the && tail -f /var/log/cron.log from the cron command.
However this will cause the Docker container to exit shortly after running because when the cron command completes, Docker thinks the last command has exited and hence kills the container. This can be avoided by running cron in the foreground via cron -f.
If you're using docker for windows, remember that you have to change your line-ending format from CRLF to LF (i.e. from dos to unix) if you intend on importing your crontab file from windows to your ubuntu container. If not, your cron-job won't work. Here's a working example:
FROM ubuntu:latest
RUN apt-get update && apt-get -y install cron
RUN apt-get update && apt-get install -y dos2unix
# Add crontab file (from your windows host) to the cron directory
ADD cron/hello-cron /etc/cron.d/hello-cron
# Change line ending format to LF
RUN dos2unix /etc/cron.d/hello-cron
# Give execution rights on the cron job
RUN chmod 0644 /etc/cron.d/hello-cron
# Apply cron job
RUN crontab /etc/cron.d/hello-cron
# Create the log file to be able to run tail
RUN touch /var/log/hello-cron.log
# Run the command on container startup
CMD cron && tail -f /var/log/hello-cron.log
This actually took me hours to figure out, as debugging cron jobs in docker containers is a tedious task. Hope it helps anyone else out there that can't get their code to work!
But: if cron dies, the container keeps running.
I created a Docker image based on the other answers, which can be used like
docker run -v "/path/to/cron:/etc/cron.d/crontab" gaafar/cron
where /path/to/cron: absolute path to crontab file, or you can use it as a base in a Dockerfile:
FROM gaafar/cron
# COPY crontab file in the cron directory
COPY crontab /etc/cron.d/crontab
# Add your commands here
For reference, the image is here.
Unfortunately, none of the above answers worked for me, although all answers lead to the solution and eventually to my solution, here is the snippet if it helps someone. Thanks
This can be solved with the bash file, due to the layered architecture of the Docker, cron service doesn't get initiated with RUN/CMD/ENTRYPOINT commands.
Simply add a bash file which will initiate the cron and other services (if required)
DockerFile
FROM gradle:6.5.1-jdk11 AS build
# apt
RUN apt-get update
RUN apt-get -y install cron
# Setup cron to run every minute to print (you can add/update your cron here)
RUN touch /var/log/cron-1.log
RUN (crontab -l ; echo "* * * * * echo testing cron.... >> /var/log/cron-1.log 2>&1") | crontab
# entrypoint.sh
RUN chmod +x entrypoint.sh
CMD ["bash","entrypoint.sh"]
entrypoint.sh
#!/bin/sh
service cron start & tail -f /var/log/cron-2.log
If any other service is also required to run along with cron then add that service with & in the same command, for example: /opt/wildfly/bin/standalone.sh & service cron start & tail -f /var/log/cron-2.log
Once you will get into the docker container there you can see that testing cron.... will be getting printed every minute in file: /var/log/cron-1.log
But, if cron dies, the container keeps running.
Define the cronjob in a dedicated container which runs the command via docker exec to your service.
This is higher cohesion and the running script will have access to the environment variables you have defined for your service.
#docker-compose.yml
version: "3.3"
services:
myservice:
environment:
MSG: i'm being cronjobbed, every minute!
image: alpine
container_name: myservice
command: tail -f /dev/null
cronjobber:
image: docker:edge
volumes:
- /var/run/docker.sock:/var/run/docker.sock
container_name: cronjobber
command: >
sh -c "
echo '* * * * * docker exec myservice printenv | grep MSG' > /etc/crontabs/root
&& crond -f"
I decided to use busybox, as it is one of the smallest images.
crond is executed in foreground (-f), logging is send to stderr (-d), I didn't choose to change the loglevel.
crontab file is copied to the default path: /var/spool/cron/crontabs
FROM busybox:1.33.1
# Usage: crond [-fbS] [-l N] [-d N] [-L LOGFILE] [-c DIR]
#
# -f Foreground
# -b Background (default)
# -S Log to syslog (default)
# -l N Set log level. Most verbose 0, default 8
# -d N Set log level, log to stderr
# -L FILE Log to FILE
# -c DIR Cron dir. Default:/var/spool/cron/crontabs
COPY crontab /var/spool/cron/crontabs/root
CMD [ "crond", "-f", "-d" ]
But output of the tasks apparently can't be seen in docker logs.
When you deploy your container on another host, just note that it won't start any processes automatically. You need to make sure that 'cron' service is running inside your container.
In our case, I am using Supervisord with other services to start cron service.
[program:misc]
command=/etc/init.d/cron restart
user=root
autostart=true
autorestart=true
stderr_logfile=/var/log/misc-cron.err.log
stdout_logfile=/var/log/misc-cron.out.log
priority=998
From above examples I created this combination:
Alpine Image & Edit Using Crontab in Nano (I hate vi)
FROM alpine
RUN apk update
RUN apk add curl nano
ENV EDITOR=/usr/bin/nano
# start crond with log level 8 in foreground, output to stderr
CMD ["crond", "-f", "-d", "8"]
# Shell Access
# docker exec -it <CONTAINERID> /bin/sh
# Example Cron Entry
# crontab -e
# * * * * * echo hello > /proc/1/fd/1 2>/proc/1/fd/2
# DATE/TIME WILL BE IN UTC
Setup a cron in parallel to a one-time job
Create a script file, say run.sh, with the job that is supposed to run periodically.
#!/bin/bash
timestamp=`date +%Y/%m/%d-%H:%M:%S`
echo "System path is $PATH at $timestamp"
Save and exit.
Use Entrypoint instead of CMD
f you have multiple jobs to kick in during docker containerization, use the entrypoint file to run them all.
Entrypoint file is a script file that comes into action when a docker run command is issued. So, all the steps that we want to run can be put in this script file.
For instance, we have 2 jobs to run:
Run once job: echo “Docker container has been started”
Run periodic job: run.sh
Create entrypoint.sh
#!/bin/bash
# Start the run once job.
echo "Docker container has been started"
# Setup a cron schedule
echo "* * * * * /run.sh >> /var/log/cron.log 2>&1
# This extra line makes it a valid cron" > scheduler.txt
crontab scheduler.txt
cron -f
Let’s understand the crontab that has been set up in the file
* * * * *: Cron schedule; the job must run every minute. You can update the schedule based on your requirement.
/run.sh: The path to the script file which is to be run periodically
/var/log/cron.log: The filename to save the output of the scheduled cron job.
2>&1: The error logs(if any) also will be redirected to the same output file used above.
Note: Do not forget to add an extra new line, as it makes it a valid cron.
Scheduler.txt: the complete cron setup will be redirected to a file.
Using System/User specific environment variables in cron
My actual cron job was expecting most of the arguments as the environment variables passed to the docker run command. But, with bash, I was not able to use any of the environment variables that belongs to the system or the docker container.
Then, this came up as a walkaround to this problem:
Add the following line in the entrypoint.sh
declare -p | grep -Ev 'BASHOPTS|BASH_VERSINFO|EUID|PPID|SHELLOPTS|UID' > /container.env
Update the cron setup and specify-
SHELL=/bin/bash
BASH_ENV=/container.env
At last, your entrypoint.sh should look like
#!/bin/bash
# Start the run once job.
echo "Docker container has been started"
declare -p | grep -Ev 'BASHOPTS|BASH_VERSINFO|EUID|PPID|SHELLOPTS|UID' > /container.env
# Setup a cron schedule
echo "SHELL=/bin/bash
BASH_ENV=/container.env
* * * * * /run.sh >> /var/log/cron.log 2>&1
# This extra line makes it a valid cron" > scheduler.txt
crontab scheduler.txt
cron -f
Last but not the least: Create a Dockerfile
FROM ubuntu:16.04
MAINTAINER Himanshu Gupta
# Install cron
RUN apt-get update && apt-get install -y cron
# Add files
ADD run.sh /run.sh
ADD entrypoint.sh /entrypoint.sh
RUN chmod +x /run.sh /entrypoint.sh
ENTRYPOINT /entrypoint.sh
That’s it. Build and run the Docker image!
Here's my docker-compose based solution:
cron:
image: alpine:3.10
command: crond -f -d 8
depends_on:
- servicename
volumes:
- './conf/cron:/etc/crontabs/root:z'
restart: unless-stopped
the lines with cron entries are on the ./conf/cron file.
Note: this won't run commands that aren't in the alpine image.
Also, output of the tasks apparently won't appear in docker logs.
This question have a lot of answers, but some are complicated and another has some drawbacks. I try to explain the problems and try to deliver a solution.
cron-entrypoint.sh:
#!/bin/bash
# copy machine environment variables to cron environment
printenv | cat - /etc/crontab > temp && mv temp /etc/crontab
## validate cron file
crontab /etc/crontab
# cron service with SIGTERM support
service cron start
trap "service cron stop; exit" SIGINT SIGTERM
# just dump your logs to std output
tail -f \
/app/storage/logs/laravel.log \
/var/log/cron.log \
& wait $!
Problems solved
environment variables are not available on cron environment (like env vars or kubernetes secrets)
stop when crontab file is not valid
stop gracefully cron jobs when machine receive an SIGTERM signal
For context, I use previous script on Kubernetes with Laravel app.
this line was the one that helped me run my pre-scheduled task.
ADD mycron/root /etc/cron.d/root
RUN chmod 0644 /etc/cron.d/root
RUN crontab /etc/cron.d/root
RUN touch /var/log/cron.log
CMD ( cron -f -l 8 & ) && apache2-foreground # <-- run cron
--> My project run inside: FROM php:7.2-apache
But: if cron dies, the container keeps running.
So, my problem was the same. The fix was to change the command section in the docker-compose.yml.
From
command: crontab /etc/crontab && tail -f /etc/crontab
To
command: crontab /etc/crontab
command: tail -f /etc/crontab
The problem was the '&&' between the commands. After deleting this, it was all fine.
Focusing on gracefully stopping the cronjobs when receiving SIGTERM or SIGQUIT signals (e.g. when running docker stop).
That's not too easy. By default, the cron process just got killed without paying attention to running cronjobs. I'm elaborating on pablorsk's answer:
Dockerfile:
FROM ubuntu:latest
RUN apt-get update \
&& apt-get -y install cron procps \
&& rm -rf /var/lib/apt/lists/*
# Copy cronjobs file to the cron.d directory
COPY cronjobs /etc/cron.d/cronjobs
# Give execution rights on the cron job
RUN chmod 0644 /etc/cron.d/cronjobs
# similarly prepare the default cronjob scripts
COPY run_cronjob.sh /root/run_cronjob.sh
RUN chmod +x /root/run_cronjob.sh
COPY run_cronjob_without_log.sh /root/run_cronjob_without_log.sh
RUN chmod +x /root/run_cronjob_without_log.sh
# Apply cron job
RUN crontab /etc/cron.d/cronjobs
# to gain access to environment variables, we need this additional entrypoint script
COPY entrypoint.sh /entrypoint.sh
RUN chmod +x /entrypoint.sh
# optionally, change received signal from SIGTERM TO SIGQUIT
#STOPSIGNAL SIGQUIT
# Run the command on container startup
ENTRYPOINT ["/entrypoint.sh"]
entrypoint.sh:
#!/bin/bash
# make global environment variables available within crond, too
printenv | grep -v "no_proxy" >> /etc/environment
# SIGQUIT/SIGTERM-handler
term_handler() {
echo 'stopping cron'
service cron stop
echo 'stopped'
echo 'waiting'
x=$(($(ps u -C run_cronjob.sh | wc -l)-1))
xold=0
while [ "$x" -gt 0 ]
do
if [ "$x" != "$xold" ]; then
echo "Waiting for $x running cronjob(s):"
ps u -C run_cronjob.sh
xold=$x
sleep 1
fi
x=$(($(ps u -C run_cronjob.sh | wc -l)-1))
done
echo 'done waiting'
exit 143; # 128 + 15 -- SIGTERM
}
# cron service with SIGTERM and SIGQUIT support
service cron start
trap "term_handler" QUIT TERM
# endless loop
while true
do
tail -f /dev/null & wait ${!}
done
cronjobs
* * * * * ./run_cronjob.sh cron1
*/2 * * * * ./run_cronjob.sh cron2
*/3 * * * * ./run_cronjob.sh cron3
Assuming you wrap all your cronjobs in a run_cronjob.sh script. That way, you can execute arbitrary code for which shutdown will wait gracefully.
run_cronjobs.sh (optional helper script to keep cronjob definitions clean)
#!/bin/bash
DIR_INCL="${BASH_SOURCE%/*}"
if [[ ! -d "$DIR_INCL" ]]; then DIR_INCL="$PWD"; fi
cd "$DIR_INCL"
# redirect all cronjob output to docker
./run_cronjob_without_log.sh "$#" > /proc/1/fd/1 2>/proc/1/fd/2
run_cronjob_without_log.sh
your_actual_cronjob_src()
Btw, when receiving a SIGKILL the container still shut downs immediately. That way you can use a command like docker-compose stop -t 60 cron-container to wait 60s for cronjobs to finish gracefully, but still terminate them for sure after the timeout.
All the answers require root access inside the container because 'cron' itself requests for UID 0.
To request root acces (e.g. via sudo) is against docker best practices.
I used https://github.com/gjcarneiro/yacron to manage scheduled tasks.
When running on some trimmed down images that restrict root access, I had to add my user to the sudoers and run as sudo cron
FROM node:8.6.0
RUN apt-get update && apt-get install -y cron sudo
COPY crontab /etc/cron.d/my-cron
RUN chmod 0644 /etc/cron.d/my-cron
RUN touch /var/log/cron.log
# Allow node user to start cron daemon with sudo
RUN echo 'node ALL=NOPASSWD: /usr/sbin/cron' >>/etc/sudoers
ENTRYPOINT sudo cron && tail -f /var/log/cron.log
Maybe that helps someone
But: if cron dies, the container keeps running.
I occasionally tried to find a docker-friendly cron implementation. And this last time I tried, I've found a couple.
By docker-friendly I mean, "output of the tasks can be seen in docker logs w/o resorting to tricks."
The most promising I see at the moment is supercronic. It can be fed a crontab file, all while being docker-friendly. To make use of it:
docker-compose.yml:
services:
supercronic:
build: .
command: supercronic crontab
Dockerfile:
FROM alpine:3.17
RUN set -x \
&& apk add --no-cache supercronic shadow \
&& useradd -m app
USER app
COPY crontab .
crontab:
* * * * * date
A gist with a bit more info.
Another good one is yacron, but it uses YAML.
ofelia can be used, but they seem to focus on running tasks in separate containers. Which is probably not a downside, but I'm not sure why I'd want to do that.
And there's also a number of traditional cron implementations: dcron, fcron, cronie. But they come with "no easy way to see output of the tasks."
Just adding to the list of answers that you can also use this image:
https://hub.docker.com/repository/docker/cronit/simple-cron
And use it as a basis to start cron jobs, using it like this:
FROM cronit/simple-cron # Inherit from the base image
#Set up all your dependencies
COPY jobs.cron ./ # Copy your local config
Evidently, it is possible to run cron as a process inside the container (under root user) alongside other processes , using ENTRYPOINT statement in Dockerfile with start.sh script what includes line process cron start. More info here
#!/bin/bash
# copy environment variables for local use
env >> etc/environment
# start cron service
service cron start
# start other service
service other start
#...
If your image doesn't contain any daemon (so it's only the short-running script or process), you may also consider starting your cron from outside, by simply defining a LABEL with the cron information, plus the scheduler itself. This way, your default container state is "exited". If you have multiple scripts, this may result in a lower footprint on your system than having multiple parallel-running cron instances.
See: https://github.com/JaciBrunning/docker-cron-label
Example docker-compose.yaml:
version: '3.8'
# Example application of the cron image
services:
cron:
image: jaci/cron-label:latest
volumes:
- "/var/run/docker.sock:/var/run/docker.sock"
- "/etc/localtime:/etc/localtime:ro"
hello:
image: hello-world
restart: "no"
labels:
- "cron.schedule=* * * * * "
I wanted to share a modification to the typical off of some of these other suggestions that I found more flexible. I wanted to enable changing the cron time with an environment variable and ended up adding an additional script that runs within my entrypoint.sh, but before the call to cron -f
*updatecron.sh*
#!/bin/sh
#remove old cron files
rm -rf /etc/cron.*/*
#create a new formatted cron definition
echo "$crondef [appname] >/proc/1/fd/1 2>/proc/1/fd/2" >> /etc/cron.d/restart-cron
echo \ >> /etc/cron.d/restart-cron
chmod 0644 /etc/cron.d/restart-cron
crontab /etc/cron.d/restart-cron
This removes any existing cron files, creates a new cronfile using an ENV variable of crondef, and then loads it.
Our's was a nodejs application to be run as cron job and it was also dependent on environment variables.
The below solution worked for us.
Docker file:
# syntax=docker/dockerfile:1
FROM node:12.18.1
ENV NODE_ENV=production
COPY ["startup.sh", "./"]
# Removed steps to build the node js application
#--------------- Setup cron ------------------
# Install Cron
RUN apt-get update
RUN apt-get -y install cron
# Run every day at 1AM
#/proc/1/fd/1 2>/proc/1/fd/2 is used to redirect cron logs to standard output and standard error
RUN (crontab -l ; echo "0 1 * * * /usr/local/bin/node /app/dist/index.js > /proc/1/fd/1 2>/proc/1/fd/2") | crontab
#--------------- Start Cron ------------------
# Grant execution rights
RUN chmod 755 startup.sh
CMD ["./startup.sh"]
startup.sh:
!/bin/bash
echo "Copying env variables to /etc/environment so that it is available for cron jobs"
printenv >> /etc/environment
echo "Starting cron"
cron -f
With multiple jobs and various dependencies like zsh and curl, this is a good approach while also combining the best practices from other answers. Bonus: This does NOT require you to set +x execution permissions on myScript.sh, which can be easy to miss in a new environment.
cron.dockerfile
FROM ubuntu:latest
# Install dependencies
RUN apt-get update && apt-get -y install \
cron \
zsh \
curl;
# Setup multiple jobs with zsh and redirect outputs to docker logs
RUN (echo "\
* * * * * zsh -c 'echo "Hello World"' 1> /proc/1/fd/1 2>/proc/1/fd/2 \n\
* * * * * zsh /myScript.sh 1> /proc/1/fd/1 2>/proc/1/fd/2 \n\
") | crontab
# Run cron in forground, so docker knows the task is running
CMD ["cron", "-f"]
Integrate this with docker compose like so:
docker-compose.yml
services:
cron:
build:
context: .
dockerfile: ./cron.dockerfile
volumes:
- ./myScript.sh:/myScript.sh
Keep in mind that you need to docker compose build cron when you change contents of the cron.dockerfile, but changes to myScript.sh will be reflected right away as it's mounted in compose.
Read a lot of topics, but couldn't understand what's going on. All is working fine before I add ENTRYPOINT to my Dockerfile. Container stops immediately without demonizing php-fpm:
FROM php:5.6-fpm
// ..Some installation instructions
# Entrypoint script
COPY ./run.sh /run.sh
RUN chmod +x /run.sh
ENTRYPOINT ["/run.sh"]
CMD ["php-fpm"]
The content of run.sh:
# Install all dependencies
php -d allow_url_fopen=on /usr/local/bin/composer install
As I understand my entrypoint will be executed with run.sh and then exited. If I will remove it then default entrypoint will be starting nginx in background. What is the best solution to run shell scripts without redefining entrypoint? Or maybe I'm talking wrong things..
ENTRYPOINT and CMD are combined to create the final COMMAND that is run when the container is started. In your case this gives:
["/run.sh", "php-fpm"]
which means that php-fpm acts as an argument to the /run.sh script. That's obviously not what you want.
You can fix this by starting php-fpm inside your script AND making sure that it runs as PID1 using exec. Running the main process as Process ID 1 assures that it will receive SIGKILL and SIGTERM interrupts (Ctrl-C for instance) and exit gracefully if possible.
# Install all dependencies
php -d allow_url_fopen=on /usr/local/bin/composer install
exec php-fpm
Your CMD should then be empty (or removed, as specifying an ENTRYPOINT also resets the CMD):
CMD []
Then in your container you can specify arguments to php-fpm via the command. Eg:
docker run -d my_php_fpm_image --help
The problem is this:
starting nginx in background
You need a process running in the foreground. If there is none, the container will exit. I think you should keep nginx running in the foreground.
To do this, use:
php-fpm -F -R
From php-fpm help:
-F, --nodaemonize force to stay in foreground, and ignore daemonize option from config file
-R, --allow-to-run-as-root Allow pool to run as root (disabled by default)
Found the way to put composer in a separate container. So i will not touch my php-fpm at all, as the best practice is one process per container.
My app container that contains all project files (composer.json, .git etc.) will provide Dockerfile:
FROM composer/composer:php5
# Set application directory
WORKDIR /var/www/html
ENTRYPOINT /usr/local/bin/composer install
CMD ["true"]
After initiating docker-compose up -d this will bring all the dependencies from composer.json into mapped directory.
I have this Docker image -
FROM centos:7
MAINTAINER Me <me.me>
RUN yum update -y
RUN yum install -y git https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
RUN yum install -y ansible
RUN git clone https://github.com/.../dockerAnsible.git
RUN ansible-playbook dockerFileBootstrap.yml
RUN (cd /lib/systemd/system/sysinit.target.wants/; for i in *; do [ $i == systemd-tmpfiles-setup.service ] || rm -f $i; done); \
rm -f /lib/systemd/system/multi-user.target.wants/*;\
rm -f /etc/systemd/system/*.wants/*;\
rm -f /lib/systemd/system/local-fs.target.wants/*; \
rm -f /lib/systemd/system/sockets.target.wants/*udev*; \
rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
rm -f /lib/systemd/system/basic.target.wants/*;\
rm -f /lib/systemd/system/anaconda.target.wants/*;
VOLUME [ "/sys/fs/cgroup" ]
EXPOSE 80 443 3306
CMD ["/usr/sbin/httpd", "-D", "FOREGROUND"]
Basically, I want it so that php-fpm starts when the docker container starts. I have php-fpm working if I manually go into the container and turn it on with /usr/sbin/php-fpm.
I tried it inside of my ansible file with this command (it didn't work). I tried using the service module as well with no luck.-
- name: Start php fpm
command: /usr/sbin/php-fpm
How can I have php-fpm running along with apache?
You should use supervisor in order to launch several services
In your dockerfile, install supervisor, then you launch
COPY ./docker/supervisord.conf /etc/supervisord.conf
....
CMD ["/usr/bin/supervisord", "-n"]
And your docker/supervisord.conf contains all the services you want to start, so you can have something like that
[program:php-fpm]
command=/opt/remi/php70/root/usr/sbin/php-fpm -c /etc/php-fpm.conf
;command=/usr/sbin/php70-fpm -c /etc/php-fpm.d
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
[program:nginx]
command=/usr/sbin/nginx
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
Of course you should adapt with your path and php-fpm versions and your services (nginx in my example, apache for you etc...), but basically supervisor is the best way to manage the start of several services from one start point.
Here you can find the official doc of docker about supervisor
https://docs.docker.com/engine/admin/using_supervisord/
I came here looking for how to run php-fpm in the foreground so it could be PID 1 in a docker container. The solution is
php-fpm -F -R
Explanation
We can check the available options with php-fpm --help
-F, --nodaemonize
force to stay in foreground, and ignore daemonize option from config file
If you are running php-fpm in a docker container, there is a good chance you are running the process as root. php-fpm won't start as root without an extra flag:
-R, --allow-to-run-as-root
Allow pool to run as root (disabled by default)
I needed similar thing recently. For alpine linux images it sufficed to run both php-fpm and a web server as the container command. Defined in Dockerfile somewhat like this:
CMD /usr/bin/php-fpm -D; nginx
ie. to daemonize php-fpm and then run nginx in foreground.
On ubuntu/debian images there is also necessary to allow starting recently installed packages by running a Dockerfile RUN command like this:
RUN echo "exit 0" > /usr/sbin/policy-rc.d
and then restart the php-fpm within a CMD command
CMD /etc/init.d/php7.0-fpm restart && nginx -g "daemon off;"
More on policy-rc.d to be found in this askubuntu question
You may find this config useful if you'd like to run php-fpm and Apache (usually using MPM Event) in the same container:
[supervisord]
[program:php-fpm]
command=php-fpm -F -R
autostart=true
autorestart=true
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
[program:apachectl]
command=apachectl -D "FOREGROUND" -k start
autostart=true
autorestart=true
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
This works for me on Docker running Ubuntu 20.04 with nginx and php-fpm.
CMD /etc/init.d/php7.4-fpm start -F && nginx -g "daemon off;"
No supervisors or cron jobs are required.
I use rc.local to start services inside a container, and then run a command inside that container to execute rc.local. So here's a sample run command:
sudo docker run --restart=always -itd --name mycontainer -p 80:80 -p 443:443 myimage/name /bin/bash -c "/etc/rc.local && while true; do echo hello world; sleep 100; done"
And this is one of the rc.local files from /etc
#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
sleep 5
service mysql start
sleep 5
service php5-fpm start
sleep 5
service nginx start
exit 0
What this does is launch a container called "mycontainer" using the image "myimage/name" with ports 80 and 443 exposed. Once launched it calls mysql, php5-fpm, and nginx to start up, pausing between each for 5 seconds. In this manner you can call any service to start that you would want to run inside that container. Remember to add open ports for those services though.
This run command will also append "Hello World" into your log file every 100 seconds as a "pulse" that will let you know when it was running and when it was stopped.
I believe #ckeeney's answer above could be accepted as the correct answer but I was unable to get it working with my particular case.
use dumb-init
I have been able to proxy PID1 through dumb-init, and daemonize PHP-FPM with the following command : dumb-init /usr/sbin/php-fpm7.2 -F -R
https://engineeringblog.yelp.com/2016/01/dumb-init-an-init-for-docker.html