OpenJDK 9: Limitations/shortcomings of the Jshell

Jshell is a quite powerful tool to do some quick explorations and to write some scripts.

If found the following limitations:

• No syntax highlighting
• Only comments with // are allowed
  if you open a script file with
   /**
    *  My comments
    */
  this will work only many warnings.
  

  |  Error:
  |  illegal start of expression
  |   * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.
  |   ^
  |  Error:
  |  illegal start of expression
  |   *
  |   ^

• The usage of public, static, ... is quite different:
  

  -> public class MyClass {
  >> public int a;
  >> };
  |  Warning:
  |  Modifier 'public'  not permitted in top-level declarations, ignored
  |  public class MyClass {
  |  ^----^
  |  Added class MyClass this error is corrected:
  |      Modifier 'public'  not permitted in top-level declarations, ignored
  |      public class MyClass {
  |      ^----^

  
  
• If you want to load a scipt with /open then tab completion does not work. The complete path including filename has to be typed / pasted.
• If you load some example snippet, main(String[] args) is not run by default.
  Just tried with the swing tutorial from oracle:
  

  jshell Downloads/HelloWorldSwing.java  

  -> String[] mystringarray;
  |  Added variable mystringarray of type String[]
  
  -> HelloWorldSwing.main(mystringarray); 

• .. 

to be continued...

Docker-CE: Creating a small Linux as base OS for running a Docker cluster

After some first steps with docker i wanted to run more than one docker node. The problem is, that i have very limited resources on my laptop.

• CoreOS (see here)
  consumes about 600MB diskspace
• UbuntuCore (see here)
  consumes about 1.9GB diskspace

To setup CoreOS you have to learn ignition - otherwise every change is lost after a reboot. For UbuntuCore you have to use an UbuntuOne account to get it running.

I heard, that Alpine Linux is an OS with a very small footprint, so i downloaded the "virtual" image and

 

mounted it in my virtualbox:

After a short startup i got the following:

This is completely different to all other installation procedures i know. No configuration dialog just a

localhost login:

You have to enter "root" and without a password you get a banner with one important information:

You can setup the system with the command: setup-alpine

This will guide you through a 11 step setup (read the manual). To get a installation with persistent homes, etc. you have to choose the "sys" mode.

And then after a reboot, i have a Linux VM with 170MB.
For my next steps (installing docker, cloning some nodes) this should be the right choice.

[Installing docker is quite easy: remove the # before "edge/community" in /etc/apk/repositories and the run "apk update" and "apk add docker".]



Related posts:

• Docker on Ubuntu 
• Running through a tutorial / investigating the processes
• Creating a small linux for my docker cluster (Alpine Linux) 
• How to build a docker swarm 
• Creating a minimal webserver container and deploying it to docker swarm
• Setting up a tomcat with docker  
• Running a swarm with multiple managers 
• Mysql inside a docker container - persistency with docker volumes 
• How to change the configuration of a standard docker container(e.g. changing tomcats memory settings)

Docker-CE: Get Started Tutorial - processes / files / HTTP headers

Inside my docker installation on ubuntu server i performed the official docker tutorial part 2: "containers"

Ok. Not really interesting, because the tutorial describes all steps very well (except the point, that you have to install python3-pip and you have to run pip3 and not pip).

Here the interesting part:

After i started the container ("docker run -p 4000:80 friendlyhello") i got the following:

root@ubuntuserver:/var/lib/docker/image# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                  NAMES
6f187950452f        friendlyhello       "python app.py"     2 hours ago         Up 2 hours          0.0.0.0:4000->80/tcp   keen_bartik

and the OS displayed

root@ubuntuserver:/var/lib/docker/image# ps x |grep docker
 5852 ?        Ssl    0:18 /usr/bin/dockerd -H fd://
 5867 ?        Ssl    0:10 docker-containerd --config /var/run/docker/containerd/containerd.toml
17100 ?        Sl     0:00 /usr/bin/docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 4000 -container-ip 172.17.0.2 -container-port 80
17105 ?        Sl     0:00 docker-containerd-shim --namespace moby --workdir /var/lib/docker/containerd/daemon/io.containerd.runtime.v1.linux/moby/6f187950452f501cf18d7efd673e8305d6c9752c58acfb14918ae37341952a11 --address /var/run/docker/containerd/docker-containerd.sock --runtime-root /var/run/docker/runtime-runc

So the containerid is part of the directory which is loaded with "--workdir"

The HTTP headers showup the following:

So the process "docker-proxy-proto" does only a portforwarding from port 4000 to port 80 and the webserver is provided by python:

Content-Type: text/html; charset=utf-8
Content-Length: 118
Server: Werkzeug/0.12.2 Python/2.7.14
Date: Sun, 19 Nov 2017 12:20:42 GMT

Here the process tree:

# pstree -al
systemd
  ├─dockerd -H fd://
  │   ├─docker-containe --config /var/run/docker/containerd/containerd.toml
  │   │   ├─docker-containe --namespace moby --workdir /var/lib/docker/containerd/daemon/io.containerd.runtime.v1.linux/moby/6f187950452f501cf18d7efd673e8305d6c9752c58acfb14918ae37341952a11 --address /var/run/docker/containerd/docker-containerd.sock --runtime-root /var/run/docker/runtime-runc
  │   │   │   ├─python app.py
  │   │   │   └─9*[{docker-containe}]
  │   │   └─7*[{docker-containe}]
  │   ├─docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 4000 -container-ip 172.17.0.2 -container-port 80
  │   │   └─4*[{docker-proxy}]
  │   └─9*[{dockerd}]

Note that this container has the ip 172.17.0.2. This is part of a private network and the ubuntu server has the ip
# ip address show docker0

3: docker0: mtu 1500 qdisc noqueue state UP group default
    link/ether 02:42:f4:04:06:3d brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 scope global docker0
       valid_lft forever preferred_lft forever

If you start the container twice

root@ubuntuserver:~/dockerapp# docker run -d -p 4000:80 friendlyhello
aebe1a25dd2dda1c36c5cdd46bbdc138099711c885a7fb270b9981301a66fbd9
root@ubuntuserver:~/dockerapp# docker run -d -p 4001:80 friendlyhello
59276d1e15d7a636dbcf4eb599f7a948365eed656d93d47097999bee9b25db6b

there are two docker-proxies running:

# ps aux|grep docker-proxy
root      1286  0.0  0.3 304928  3084 ?        Sl   16:16   0:00 /usr/bin/docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 4000 -container-ip 172.17.0.2 -container-port 80
root      1385  0.0  0.2 304928  2880 ?        Sl   16:16   0:00 /usr/bin/docker-proxy -proto tcp -host-ip 0.0.0.0 -host-port 4001 -container-ip 172.17.0.3 -container-port 80

Related posts:

• Docker on Ubuntu 
• Running through a tutorial / investigating the processes
• Creating a small linux for my docker cluster (Alpine Linux) 
• How to build a docker swarm 
• Creating a minimal webserver container and deploying it to docker swarm
• Setting up a tomcat with docker  
• Running a swarm with multiple managers 
• Mysql inside a docker container - persistency with docker volumes 
• How to change the configuration of a standard docker container(e.g. changing tomcats memory settings)

Docker-CE: initial configuration

After installing docker to a ubuntu server i was keen what kind of processes and files are there.

# ps x|grep docker
 5852 ?        Ssl    0:05 /usr/bin/dockerd -H fd://
 5867 ?        Ssl    0:04 docker-containerd --config /var/run/docker/containerd/containerd.toml

So the inital configuration is not stored in /etc.

The configuration file looks like this:

# cat /var/run/docker/containerd/containerd.toml
root = "/var/lib/docker/containerd/daemon"
state = "/var/run/docker/containerd/daemon"
subreaper = false
oom_score = -500

[grpc]
  address = "/var/run/docker/containerd/docker-containerd.sock"
  uid = 0
  gid = 0

[debug]
  address = "/var/run/docker/containerd/docker-containerd-debug.sock"
  uid = 0
  gid = 0
  level = "info"

[metrics]
  address = ""

[cgroup]
  path = ""

[plugins]
  [plugins.linux]
    shim = "docker-containerd-shim"
    runtime = "docker-runc"
    runtime_root = "/var/lib/docker/runc"
    no_shim = false
    shim_debug = false
    shim_no_newns = false

The directory /var/run/docker/containerd/daemon seems to be important, so let's take a look:

# find /var/run/docker/containerd/daemon
/var/run/docker/containerd/daemon
/var/run/docker/containerd/daemon/io.containerd.runtime.v1.linux
/var/run/docker/containerd/daemon/io.containerd.runtime.v1.linux/moby

But theese entries are only directories...

So what about /var/lib? Here we go:

# find /var/lib/docker/ -maxdepth 1
/var/lib/docker/
/var/lib/docker/overlay2
/var/lib/docker/swarm
/var/lib/docker/image
/var/lib/docker/tmp
/var/lib/docker/runtimes
/var/lib/docker/trust
/var/lib/docker/plugins
/var/lib/docker/containerd
/var/lib/docker/containers
/var/lib/docker/builder
/var/lib/docker/volumes
/var/lib/docker/network

Within the directory containers you can find information about the containers which run / ran on your docker system:

# ls -l
insgesamt 12
drwx------ 4 root root 4096 Nov 16 22:12 0c7567bb965449f5f2f3dfadfc38f0226bdb42cc6d46daa4641042090e0405c7
drwx------ 4 root root 4096 Nov 16 22:57 28b7f70147aabc94bd174ce7ad7f5d48ed5610ffaa21733d3549ee6e998ee7c3
drwx------ 4 root root 4096 Nov 16 21:59 2db1c3ed1dafc85369536c382e02b6a23e5d134d2ba3d56a738f3441fb624b04

 The first characters of the directories match the container-id:

# docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                  PORTS               NAMES
28b7f70147aa        hello-world         "/hello"            2 days ago          Exited (0) 2 days ago                       trusting_bartik
0c7567bb9654        hello-world         "/hello"            2 days ago          Exited (0) 2 days ago                       festive_wozniak
2db1c3ed1daf        hello-world         "/hello"            2 days ago          Exited (0) 2 days ago                       epic_tesla

Related posts:

• Docker on Ubuntu 
• Running through a tutorial / investigating the processes
• Creating a small linux for my docker cluster (Alpine Linux) 
• How to build a docker swarm 
• Creating a minimal webserver container and deploying it to docker swarm
• Setting up a tomcat with docker  
• Running a swarm with multiple managers 
• Mysql inside a docker container - persistency with docker volumes 
• How to change the configuration of a standard docker container(e.g. changing tomcats memory settings)