I have an Azure Container Instance that has a non root user as default. For debugging and experimentation, I'd like to exec into the container like you would with a normal docker container: docker exec -u root ..., so that I have sudo permissions in the container. As detailed in Interacting with a container in Azure Container Instances, you can run exec commands through az container exec ..., but as was mentioned in Christian's answer, https://stackoverflow.com/a/50334426/17129046, there doesn't seem to be a way to add extra parameters, not just for the program being run, but there also doesn't seem to be support for any of the additional options you'd have with docker exec, including the -u option to change the user that logs in to the container when running docker exec -u root ... '/bin/bash'.
I have tried using su in the container, but it prompts for a password, and I don't know what that password would be, since the dockerfile that created the image this ACI uses doesn't set a password as far as I know (The image is created via bentoml). The default user is called bentoml. Result from running id:
uid=1034(bentoml) gid=1034(bentoml) groups=1034(bentoml)
Is there a workaround for this? Maybe a way to ssh into the container as root?
I tried to reproduce the issue and got the below output
I have pulled the docker image from the docker hub using below command
docker pull <image_name>
While pulling the image from docker we need to give the credentials if it ask
I have run the image using below command
docker run -it <image_id> /bin/bash
Here the container is running and I am not able to use root user commands
For accessing container as root use the below command
docker run -u 0 -it image_id /bin/bash
Here I can able to install all root packages now
You can use this docker file for setting the no password then it won't ask any password
RUN apt-get update \
&& apt-get install -y sudo
RUN adduser --disabled-password --gecos '' docker
RUN adduser docker sudo
RUN echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
USER docker
I have a working oracle image, which I can use run then use docker exec to get into the running container and execute sqlplus command with no issue.
Now I am trying to create a new image with some initial data using this image. Here is my docker file.
FROM oracle:12.2
USER root
COPY /testingData /testingData
RUN chown -R oracle:oinstall /testingData
RUN chmod -R 755 /testingData
USER oracle
RUN /testingData/runInitSQLScript.sh
And here is my sh file
#!/bin/bash
sqlplus -s /nolog << EOF
CONNECT sys as SYSDBA/testpass;
whenever sqlerror exit sql.sqlcode;
set echo off
set heading off
#/sql/mytestingData.sql
exit;
EOF
It kept telling me sqlplus command not found
When I try to use the full path of the sqlplus like this #ORACLE_HOME/bin/sqlplus, it still says the same. Then I tried to check on the path, I realize I can only get into one layer under the root directory, for example, if my ORACLE_HOME is /u01/app/oracle/product/12.2.0/dbhome_1/, I can only cd into /u01, when I do cd /u01/app, it start to say that directory not found. Please help. Thanks.
If you image is similar to official images, it installs Oracle software and creates database only after the start of container. So at the moment when you create image, ORACLE_HOME directory doesn't exist yet.
In case of official images, I'd suggest you to put your scripts into one of these 2 special folders:
-v /opt/oracle/scripts/startup | /docker-entrypoint-initdb.d/startup
Optional: A volume with custom scripts to be run after database startup.
For further details see the "Running scripts after setup and on startup" section below.
-v /opt/oracle/scripts/setup | /docker-entrypoint-initdb.d/setup
Optional: A volume with custom scripts to be run after database setup.
For further details see the "Running scripts after setup and on startup" section below.
More about this: https://github.com/oracle/docker-images/tree/master/OracleDatabase/SingleInstance
update:
As per #Sayan comment the sqlplus exist on $ORACLE_HOME/bin/sqlplus path.
OR
the other option is to use below docker image to connect with Oracle database container
docker run --interactive guywithnose/sqlplus sqlplus {CONNECTION_STRING}
or use legacy linking to better to use docker network
docker run --it --link db guywithnose/sqlplus sqlplus {CONNECTION_STRING}
Now you can use db as host name for db connection.
https://github.com/sflyr/docker-sqlplus
I have a very simple dockerfile with only one row, namely "FROM ubuntu". I created an image from this dockerfile by the command docker build -t ubuntu_ .
I know that I can create a new docker container from this image an run it interactively with the command
docker run -it my_new_container
I can later start this new container with the command
start my_new container
As I understand it, I should also be able to use this container it interactively by
start -i my_new container
But, it does not work. It just runs and exits. I don't get to the container's command prompt as I do when I use run. What am I doing wrong?
If i understood correctly, you want to see the logs from container in terminal, same as when you run the image with docker run. If that's the case, then try with
docker start -a my_docker_container
You can enter a running container with:
docker exec -it <container name> /bin/bash
example:
docker exec -it my_new_container /bin/bash
you can replace bash with sh if bash is not available in the container.
and if you need to explicitly use a UID , like root = UID 0, you can specify this:
docker exec -it -u 0 my_new_container /bin/bash
which will log you as root
Direct answer:
To run an interactive shell for a non-running container, first find the image that the container is based on.
Then:
docker container run -it [yourImage] bash
If your eventual container is based on an alpine image, replace bash with sh.
Technically, this will create a NEW container, but it gets the job done.
EDIT [preferred method]:
An even better way is to give the container something irrelevant to do. A nice solution from the VSCode docs is to put the following command into your service definition of the docker-compose.yml file:
services:
my-app-service:
command: ["sleep", "infinity"]
# other relevant parts of your service def...
The idea here is that you're telling your container to sleep for some time (infinite amount of time). Ironically, this your container will have to maintain this state, forcing the container to keep running.
This is how I run containers. Best wishes to whomever needs this nugget of info. We're all learning :)
You cannot get a shell into a container in its stopped state, or restart it directly with another entry point. If the container keeps exiting and you need to examine it, the only option I know of is to commit the container as a new image and then start a new container with such image, as per a related answer.
If you don't need that container anymore and just want it to stay up, you should run it with a process that will not exit. An example with an Ubuntu image would be (you don't need a Dockerfile for this):
docker run -d ubuntu --name carrot tail -f /dev/null
You will see that this container stays up and you can now run bash on it, to access the CLI:
docker exec -ti carrot bash
If the container has stopped for whatever reason, such as a machine restart, you can bring it back up:
docker start carrot
And it will continue to stay up again.
I've noticed with docker that I need to understand what's happening inside a container or what files exist in there. One example is downloading images from the docker index - you don't have a clue what the image contains so it's impossible to start the application.
What would be ideal is to be able to ssh into them or equivalent. Is there a tool to do this, or is my conceptualisation of docker wrong in thinking I should be able to do this.
Here are a couple different methods...
A) Use docker exec (easiest)
Docker version 1.3 or newer supports the command exec that behave similar to nsenter. This command can run new process in already running container (container must have PID 1 process running already). You can run /bin/bash to explore container state:
docker exec -t -i mycontainer /bin/bash
see Docker command line documentation
B) Use Snapshotting
You can evaluate container filesystem this way:
# find ID of your running container:
docker ps
# create image (snapshot) from container filesystem
docker commit 12345678904b5 mysnapshot
# explore this filesystem using bash (for example)
docker run -t -i mysnapshot /bin/bash
This way, you can evaluate filesystem of the running container in the precise time moment. Container is still running, no future changes are included.
You can later delete snapshot using (filesystem of the running container is not affected!):
docker rmi mysnapshot
C) Use ssh
If you need continuous access, you can install sshd to your container and run the sshd daemon:
docker run -d -p 22 mysnapshot /usr/sbin/sshd -D
# you need to find out which port to connect:
docker ps
This way, you can run your app using ssh (connect and execute what you want).
D) Use nsenter
Use nsenter, see Why you don't need to run SSHd in your Docker containers
The short version is: with nsenter, you can get a shell into an
existing container, even if that container doesn’t run SSH or any kind
of special-purpose daemon
UPDATE: EXPLORING!
This command should let you explore a running docker container:
docker exec -it name-of-container bash
The equivalent for this in docker-compose would be:
docker-compose exec web bash
(web is the name-of-service in this case and it has tty by default.)
Once you are inside do:
ls -lsa
or any other bash command like:
cd ..
This command should let you explore a docker image:
docker run --rm -it --entrypoint=/bin/bash name-of-image
once inside do:
ls -lsa
or any other bash command like:
cd ..
The -it stands for interactive... and tty.
This command should let you inspect a running docker container or image:
docker inspect name-of-container-or-image
You might want to do this and find out if there is any bash or sh in there. Look for entrypoint or cmd in the json return.
NOTE: This answer relies on commen tool being present, but if there is no bash shell or common tools like ls present you could first add one in a layer if you have access to the Dockerfile:
example for alpine:
RUN apk add --no-cache bash
Otherwise if you don't have access to the Dockerfile then just copy the files out of a newly created container and look trough them by doing:
docker create <image> # returns container ID the container is never started.
docker cp <container ID>:<source_path> <destination_path>
docker rm <container ID>
cd <destination_path> && ls -lsah
see docker exec documentation
see docker-compose exec documentation
see docker inspect documentation
see docker create documentation
In case your container is stopped or doesn't have a shell (e.g. hello-world mentioned in the installation guide, or non-alpine traefik), this is probably the only possible method of exploring the filesystem.
You may archive your container's filesystem into tar file:
docker export adoring_kowalevski > contents.tar
Or list the files:
docker export adoring_kowalevski | tar t
Do note, that depending on the image, it might take some time and disk space.
Before Container Creation :
If you to explore the structure of the image that is mounted inside the container you can do
sudo docker image save image_name > image.tar
tar -xvf image.tar
This would give you the visibility of all the layers of an image and its configuration which is present in json files.
After container creation :
For this there are already lot of answers above. my preferred way to do
this would be -
docker exec -t -i container /bin/bash
The most upvoted answer is working for me when the container is actually started, but when it isn't possible to run and you for example want to copy files from the container this has saved me before:
docker cp <container-name>:<path/inside/container> <path/on/host/>
Thanks to docker cp (link) you can copy directly from the container as it was any other part of your filesystem.
For example, recovering all files inside a container:
mkdir /tmp/container_temp
docker cp example_container:/ /tmp/container_temp/
Note that you don't need to specify that you want to copy recursively.
The file system of the container is in the data folder of docker, normally in /var/lib/docker. In order to start and inspect a running containers file system do the following:
hash=$(docker run busybox)
cd /var/lib/docker/aufs/mnt/$hash
And now the current working directory is the root of the container.
you can use dive to view the image content interactively with TUI
https://github.com/wagoodman/dive
Try using
docker exec -it <container-name> /bin/bash
There might be possibility that bash is not implemented. for that you can use
docker exec -it <container-name> sh
On Ubuntu 14.04 running Docker 1.3.1, I found the container root filesystem on the host machine in the following directory:
/var/lib/docker/devicemapper/mnt/<container id>/rootfs/
Full Docker version information:
Client version: 1.3.1
Client API version: 1.15
Go version (client): go1.3.3
Git commit (client): 4e9bbfa
OS/Arch (client): linux/amd64
Server version: 1.3.1
Server API version: 1.15
Go version (server): go1.3.3
Git commit (server): 4e9bbfa
In my case no shell was supported in container except sh. So, this worked like a charm
docker exec -it <container-name> sh
The most voted answer is good except if your container isn't an actual Linux system.
Many containers (especially the go based ones) don't have any standard binary (no /bin/bash or /bin/sh). In that case, you will need to access the actual containers file directly:
Works like a charm:
name=<name>
dockerId=$(docker inspect -f {{.Id}} $name)
mountId=$(cat /var/lib/docker/image/aufs/layerdb/mounts/$dockerId/mount-id)
cd /var/lib/docker/aufs/mnt/$mountId
Note: You need to run it as root.
I use another dirty trick that is aufs/devicemapper agnostic.
I look at the command that the container is running e.g. docker ps
and if it's an apache or java i just do the following:
sudo -s
cd /proc/$(pgrep java)/root/
and voilá you're inside the container.
Basically you can as root cd into /proc/<PID>/root/ folder as long as that process is run by the container. Beware symlinks will not make sense wile using that mode.
Only for LINUX
The most simple way that I use was using proc dir, the container must be running in order to inspect the docker container files.
Find out the process id (PID) of the container and store it into some variable
PID=$(docker inspect -f '{{.State.Pid}}' your-container-name-here)
Make sure the container process is running, and use the variable name to get into the container folder
cd /proc/$PID/root
If you want to get through the dir without finding out the PID number, just use this long command
cd /proc/$(docker inspect -f '{{.State.Pid}}' your-container-name-here)/root
Tips:
After you get inside the container, everything you do will affect the actual process of the container, such as stopping the service or changing the port number.
Hope it helps
Note:
This method only works if the container is still running, otherwise, the directory wouldn't exist anymore if the container has stopped or removed
None of the existing answers address the case of a container that exited (and can't be restarted) and/or doesn't have any shell installed (e.g. distroless ones). This one works as long has you have root access to the Docker host.
For a real manual inspection, find out the layer IDs first:
docker inspect my-container | jq '.[0].GraphDriver.Data'
In the output, you should see something like
"MergedDir": "/var/lib/docker/overlay2/03e8df748fab9526594cfdd0b6cf9f4b5160197e98fe580df0d36f19830308d9/merged"
Navigate into this folder (as root) to find the current visible state of the container filesystem.
This will launch a bash session for the image:
docker run --rm -it --entrypoint=/bin/bash
On newer versions of Docker you can run docker exec [container_name] which runs a shell inside your container
So to get a list of all the files in a container just run docker exec [container_name] ls
I wanted to do this, but I was unable to exec into my container as it had stopped and wasn't starting up again due to some error in my code.
What worked for me was to simply copy the contents of the entire container into a new folder like this:
docker cp container_name:/app/ new_dummy_folder
I was then able to explore the contents of this folder as one would do with a normal folder.
For me, this one works well (thanks to the last comments for pointing out the directory /var/lib/docker/):
chroot /var/lib/docker/containers/2465790aa2c4*/root/
Here, 2465790aa2c4 is the short ID of the running container (as displayed by docker ps), followed by a star.
For docker aufs driver:
The script will find the container root dir(Test on docker 1.7.1 and 1.10.3 )
if [ -z "$1" ] ; then
echo 'docker-find-root $container_id_or_name '
exit 1
fi
CID=$(docker inspect --format {{.Id}} $1)
if [ -n "$CID" ] ; then
if [ -f /var/lib/docker/image/aufs/layerdb/mounts/$CID/mount-id ] ; then
F1=$(cat /var/lib/docker/image/aufs/layerdb/mounts/$CID/mount-id)
d1=/var/lib/docker/aufs/mnt/$F1
fi
if [ ! -d "$d1" ] ; then
d1=/var/lib/docker/aufs/diff/$CID
fi
echo $d1
fi
This answer will help those (like myself) who want to explore the docker volume filesystem even if the container isn't running.
List running docker containers:
docker ps
=> CONTAINER ID "4c721f1985bd"
Look at the docker volume mount points on your local physical machine (https://docs.docker.com/engine/tutorials/dockervolumes/):
docker inspect -f {{.Mounts}} 4c721f1985bd
=> [{ /tmp/container-garren /tmp true rprivate}]
This tells me that the local physical machine directory /tmp/container-garren is mapped to the /tmp docker volume destination.
Knowing the local physical machine directory (/tmp/container-garren) means I can explore the filesystem whether or not the docker container is running. This was critical to helping me figure out that there was some residual data that shouldn't have persisted even after the container was not running.
If you are using Docker v19.03, you follow the below steps.
# find ID of your running container:
docker ps
# create image (snapshot) from container filesystem
docker commit 12345678904b5 mysnapshot
# explore this filesystem
docker run -t -i mysnapshot /bin/sh
For an already running container, you can do:
dockerId=$(docker inspect -f {{.Id}} [docker_id_or_name])
cd /var/lib/docker/btrfs/subvolumes/$dockerId
You need to be root in order to cd into that dir. If you are not root, try 'sudo su' before running the command.
Edit: Following v1.3, see Jiri's answer - it is better.
another trick is to use the atomic tool to do something like:
mkdir -p /path/to/mnt && atomic mount IMAGE /path/to/mnt
The Docker image will be mounted to /path/to/mnt for you to inspect it.
My preferred way to understand what is going on inside container is:
expose -p 8000
docker run -it -p 8000:8000 image
Start server inside it
python -m SimpleHTTPServer
If you are using the AUFS storage driver, you can use my docker-layer script to find any container's filesystem root (mnt) and readwrite layer :
# docker-layer musing_wiles
rw layer : /var/lib/docker/aufs/diff/c83338693ff190945b2374dea210974b7213bc0916163cc30e16f6ccf1e4b03f
mnt : /var/lib/docker/aufs/mnt/c83338693ff190945b2374dea210974b7213bc0916163cc30e16f6ccf1e4b03f
Edit 2018-03-28 :
docker-layer has been replaced by docker-backup
The docker exec command to run a command in a running container can help in multiple cases.
Usage: docker exec [OPTIONS] CONTAINER COMMAND [ARG...]
Run a command in a running container
Options:
-d, --detach Detached mode: run command in the background
--detach-keys string Override the key sequence for detaching a
container
-e, --env list Set environment variables
-i, --interactive Keep STDIN open even if not attached
--privileged Give extended privileges to the command
-t, --tty Allocate a pseudo-TTY
-u, --user string Username or UID (format:
[:])
-w, --workdir string Working directory inside the container
For example :
1) Accessing in bash to the running container filesystem :
docker exec -it containerId bash
2) Accessing in bash to the running container filesystem as root to be able to have required rights :
docker exec -it -u root containerId bash
This is particularly useful to be able to do some processing as root in a container.
3) Accessing in bash to the running container filesystem with a specific working directory :
docker exec -it -w /var/lib containerId bash
Often times I only need to explore the docker filesystem because my build won't run, so docker run -it <container_name> bash is impractical. I also do not want to waste time and memory copying filesystems, so docker cp <container_name>:<path> <target_path> is impractical too.
While possibly unorthodox, I recommend re-building with ls as the final command in the Dockerfile:
CMD [ "ls", "-R" ]
I've found the easiest, all-in-one solution to View, Edit, Copy files with a GUI app inside almost any running container.
mc editing files in docker
inside the container install mc and ssh: docker exec -it <container> /bin/bash, then with prompt install mc and ssh packages
in same exec-bash console, run mc
press ESC then 9 then ENTER to open menu and select "Shell link..."
using "Shell link..." open SCP-based filesystem access to any host with ssh server running (including the one running docker) by it's IP address
do your job in graphical UI
this method overcomes all issues with permissions, snap isolation etc., allows to copy directly to any machine and is the most pleasant to use for me
I had an unknown container, that was doing some production workload and did not want to run any command.
So, I used docker diff.
This will list all files that the container had changed and therefore good suited to explore the container file system.
To get only a folder you can just use grep:
docker diff <container> | grep /var/log
It will not show files from the docker image. Depending on your use case this can help or not.
Late to the party, but in 2022 we have VS Code