Override parent image docker container command to do something after - docker

Question

I want to change a user password and run a SQL script against a DB2 container image. How do I do whatever the parent image called for, but then run a few commands after that completed? I need this to run using docker compose because the database will be used to support an acceptance test. In my docker-compose.yml file, I have a command property, but I checked the container and do not see the result of the touch statement, so it never ran.
My docker-compose.yml file is:
version: "3.2"
services:
ssc-file-generator-db2-test:
container_name: "ssc-file-generator-db2-test"
image: ibmcom/db2:latest
command: /bin/bash -c "touch /command-run && echo \"db2inst1:db2inst1\" | chpasswd && su db2inst1 && db2 -tvf /db2-test-scaffolding/init.sql"
hostname: db2server
privileged: true
# entrypoint: ["/bin/sh -c ]
ports:
- 50100:50000
- 55100:55000
networks:
- back-tier
restart: "no"
volumes:
- db2-test-scaffolding:/db2-test-scaffolding
env_file:
- acceptance-run.environment
# ssc-file-generator:
# container_name: "ssc-file-generator_testing"
# image: ssc-file-generator
# depends_on: ["ssc-file-generator-db2-test]
# command:
# env_file: ["acceptance-run.environment"]
networks:
back-tier: {}
volumes:
db2-test-scaffolding:
driver: local
driver_opts:
o: bind
type: none
device: ./db2-test-scaffolding
acceptance-run.environment
BCUPLOAD_DATASOURCE_DIALECT=org.hibernate.dialect.DB2Dialect
BCUPLOAD_DATASOURCE_DRIVER=com.ibm.db2.jcc.DB2Driver
BCUPLOAD_DATASOURCE_PASSWORD=bluecost
BCUPLOAD_DATASOURCE_URL=jdbc:db2://localhost:50100/mydb:currentSchema=FILE_GENERATOR
BCUPLOAD_DATASOURCE_USERNAME=bluecost
B2INSTANCE=db2inst1
DB2INST1_PASSWORD=db2inst1
DBNAME=MYDB
DEBUG_SECRETS=true
file-generator.test.files.path=src/test/acceptance/resources/files/
# Needed for DB2 container
LICENSE=accept
The docker image is
ibmcom/db2:latest
For convenience, this is the docker inspect ibmcom/db2:latest
[
{
"Id": "sha256:e304e217603b80b31c989574081b2badf210b4466c7f74cf32087ee0a1ba6e04",
"RepoTags": [
"ibmcom/db2:latest"
],
"RepoDigests": [
"ibmcom/db2#sha256:77da4492bf18c49a1012aa6071a16aee0039dca9c0a2a492345b6b030714a54f"
],
"Parent": "",
"Comment": "",
"Created": "2021-03-29T18:54:36.94484751Z",
"Container": "e59bda8065b72a0e440d145d6d90ba77231a514e811e66651d4fa6da98a34910",
"ContainerConfig": {
"Hostname": "6125cd0dc6e6",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"ExposedPorts": {
"22/tcp": {},
"50000/tcp": {},
"55000/tcp": {},
"60006/tcp": {},
"60007/tcp": {}
},
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"container=oci",
"STORAGE_DIR=/database",
"HADR_SHARED_DIR=/hadr",
"DBPORT=50000",
"TSPORT=55000",
"SETUPDIR=/var/db2_setup",
"SETUPAREA=/tmp/setup",
"NOTVISIBLE=in users profile",
"LICENSE_NAME=db2dec.lic"
],
"Cmd": [
"/bin/sh",
"-c",
"#(nop) ",
"ENTRYPOINT [\"/var/db2_setup/lib/setup_db2_instance.sh\"]"
],
"Image": "sha256:e65b35603167c75a86515ef4af101a539cbbdf561bcb9efd656d17b8d867c7da",
"Volumes": {
"/database": {},
"/hadr": {}
},
"WorkingDir": "",
"Entrypoint": [
"/var/db2_setup/lib/setup_db2_instance.sh"
],
"OnBuild": [],
"Labels": {
"architecture": "x86_64",
"build-date": "2021-03-10T06:09:00.139818",
"com.redhat.build-host": "cpt-1007.osbs.prod.upshift.rdu2.redhat.com",
"com.redhat.component": "ubi7-container",
"com.redhat.license_terms": "https://www.redhat.com/en/about/red-hat-end-user-license-agreements#UBI",
"description": "The Universal Base Image is designed and engineered to be the base layer for all of your containerized applications, middleware and utilities. This base image is freely redistributable, but Red Hat only supports Red Hat technologies through subscriptions for Red Hat products. This image is maintained by Red Hat and updated regularly.",
"distribution-scope": "public",
"io.k8s.description": "The Universal Base Image is designed and engineered to be the base layer for all of your containerized applications, middleware and utilities. This base image is freely redistributable, but Red Hat only supports Red Hat technologies through subscriptions for Red Hat products. This image is maintained by Red Hat and updated regularly.",
"io.k8s.display-name": "Red Hat Universal Base Image 7",
"io.openshift.tags": "base rhel7",
"name": "ubi7",
"release": "338",
"summary": "Provides the latest release of the Red Hat Universal Base Image 7.",
"url": "https://access.redhat.com/containers/#/registry.access.redhat.com/ubi7/images/7.9-338",
"vcs-ref": "a4e710a688a6374670ecdd56637c3f683d11cbe3",
"vcs-type": "git",
"vendor": "Red Hat, Inc.",
"version": "7.9"
}
},
"DockerVersion": "19.03.6",
"Author": "db2_download_and_go",
"Config": {
"Hostname": "6125cd0dc6e6",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"ExposedPorts": {
"22/tcp": {},
"50000/tcp": {},
"55000/tcp": {},
"60006/tcp": {},
"60007/tcp": {}
},
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"container=oci",
"STORAGE_DIR=/database",
"HADR_SHARED_DIR=/hadr",
"DBPORT=50000",
"TSPORT=55000",
"SETUPDIR=/var/db2_setup",
"SETUPAREA=/tmp/setup",
"NOTVISIBLE=in users profile",
"LICENSE_NAME=db2dec.lic"
],
"Cmd": null,
"Image": "sha256:e65b35603167c75a86515ef4af101a539cbbdf561bcb9efd656d17b8d867c7da",
"Volumes": {
"/database": {},
"/hadr": {}
},
"WorkingDir": "",
"Entrypoint": [
"/var/db2_setup/lib/setup_db2_instance.sh"
],
"OnBuild": [],
"Labels": {
"architecture": "x86_64",
"build-date": "2021-03-10T06:09:00.139818",
"com.redhat.build-host": "cpt-1007.osbs.prod.upshift.rdu2.redhat.com",
"com.redhat.component": "ubi7-container",
"com.redhat.license_terms": "https://www.redhat.com/en/about/red-hat-end-user-license-agreements#UBI",
"description": "The Universal Base Image is designed and engineered to be the base layer for all of your containerized applications, middleware and utilities. This base image is freely redistributable, but Red Hat only supports Red Hat technologies through subscriptions for Red Hat products. This image is maintained by Red Hat and updated regularly.",
"distribution-scope": "public",
"io.k8s.description": "The Universal Base Image is designed and engineered to be the base layer for all of your containerized applications, middleware and utilities. This base image is freely redistributable, but Red Hat only supports Red Hat technologies through subscriptions for Red Hat products. This image is maintained by Red Hat and updated regularly.",
"io.k8s.display-name": "Red Hat Universal Base Image 7",
"io.openshift.tags": "base rhel7",
"name": "ubi7",
"release": "338",
"summary": "Provides the latest release of the Red Hat Universal Base Image 7.",
"url": "https://access.redhat.com/containers/#/registry.access.redhat.com/ubi7/images/7.9-338",
"vcs-ref": "a4e710a688a6374670ecdd56637c3f683d11cbe3",
"vcs-type": "git",
"vendor": "Red Hat, Inc.",
"version": "7.9"
}
},
"Architecture": "amd64",
"Os": "linux",
"Size": 2778060115,
"VirtualSize": 2778060115,
"GraphDriver": {
"Data": {
"LowerDir": "/var/lib/docker/overlay2/49d83ba2eb50cdbfc5a9e3a7b4baf907a9b4326aa0710689f602bb3cff01d820/diff:/var/lib/docker/overlay2/ba54659cc4ec10fa84edc49d5480ebe4897629f841d76ae79a4fb0c2edb791a5/diff:/var/lib/docker/overlay2/2238ae349d70686609b990b63c0066d6e51d94be59801a81c7f5b4d97da1fe02/diff:/var/lib/docker/overlay2/704708b72448f8a4750db3aabd43c12f23ad7e6d3f727aa5977bd7ac4db8e8cb/diff:/var/lib/docker/overlay2/1b47e1515517af553fd8b986c841e87d8ba813d53739344c9b7350ad36b54b0b/diff:/var/lib/docker/overlay2/0a580802a7096343aa5d8de5039cf5a011e66e481793230dced8769b024e5cd2/diff:/var/lib/docker/overlay2/4da91655770b0e94236ea8da2ea8ff503467161cf85473a32760f89b56d213ff/diff:/var/lib/docker/overlay2/401c640771a27c70f20abf5c48b0be0e2f42ed5b022f81f58ebc0810831283ea/diff:/var/lib/docker/overlay2/8985c59d1ab32b8d8eaf4c11890801cb228d47cc7437b3e9b4f585e7296e4b6a/diff:/var/lib/docker/overlay2/ec66f9872de7b5310bac2bd5fd59552574df56bb06dcd5dd61ff2b63002d77ed/diff:/var/lib/docker/overlay2/fcf40217c8477dcf4e5fafc8c83408c3c788f367ed67c78cb0bc312439674fcf/diff",
"MergedDir": "/var/lib/docker/overlay2/8bcf7bf60181d555a11fb8df79a28cb2f9d8737d28fe913a252694ba2165c1d1/merged",
"UpperDir": "/var/lib/docker/overlay2/8bcf7bf60181d555a11fb8df79a28cb2f9d8737d28fe913a252694ba2165c1d1/diff",
"WorkDir": "/var/lib/docker/overlay2/8bcf7bf60181d555a11fb8df79a28cb2f9d8737d28fe913a252694ba2165c1d1/work"
},
"Name": "overlay2"
},
"RootFS": {
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"Metadata": {
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}
}
]

Answer 1

I solved the problem by debugging the bash script and learning that it offers a custom directory which by which it runs scripts. I believe these get run after the db2 service starts. While I suspect that I could have specified an entrypoint, it would not necessarily work well with the ibmcom/db2 container. Posted below is my docker compose file showing volume mounts which I used for this particular container.
Note I think this defines mounts in a "bind" format, I believe, as opposed to a more common volume. My approach allowed me to pick where the source data is stored, whereas had I specified a volume, it would have picked some bizarre place on my WSL system to persist the volume data. There's probably a better approach, but I'm still learning Docker builds.
version: "3.2"
services:
ssc-file-generator-db2-test:
container_name: "ssc-file-generator-db2-test"
image: ibmcom/db2:latest
hostname: db2server
privileged: true
ports:
- 50100:50000
- 55100:55000
networks:
- back-tier
restart: "no"
volumes:
- setup-sql:/setup-sql
- db2-shell-scripts:/var/custom
- host-dirs:/host-dirs
# Uncomment below to use database outside the container
# - database:/database
env_file:
- acceptance-run.environment
networks:
back-tier: {}
volumes:
setup-sql:
driver: local
driver_opts:
o: bind
type: none
device: ./setup-sql
db2-shell-scripts:
driver: local
driver_opts:
o: bind
type: none
device: ./db2-shell-scripts
host-dirs:
driver: local
driver_opts:
o: bind
type: none
device: ./host-dirs