Python

• install
• dnf install -y python-devel
• dnf install libtiff-devel libjpeg-devel libzip-devel freetype-devel lcms2-devel libwebp-devel tcl-devel tk-devel
• graph
• PIL: pip install Image
• dnf install tkinter
• pip install matplotlib
• subprocess.Popen
• def subprocess_Popen(cmd, wait = True):
•     pipe = subprocess.Popen(cmd, shell = True, stdin = subprocess.PIPE, stdout = subprocess.PIPE, stderr = subprocess.PIPE)
•     outs, errs = pipe.communicate()
•     if (outs):
•         print(outs)
•     if (errs):
•         print(errs)
• Django
• http://pythonstudy.xyz/python/article/312-Django-%ED%85%9C%ED%94%8C%EB%A6%BF-%ED%99%95%EC%9E%A5
• 
  

Docker

• Installation
• dnf install docker
• systemctl start docker
• systemctl enable docker
• sudo groupadd docker
• sudo gpasswd -a ${USER} docker
• sudo systemctl restart docker
• docker pull fedora
• docker save -o <save image to pathj> <image name>
• docker load -i <path to image tar file>
• docker images, docker ps, docker rmi, docker rm
• docker run -v /home:/home --rm=true -i -t docker.io/fedora /bin/bash
• docker run --rm -it docker_test_1 /bin/bash
• docker commit <image> <image_name>
• docker history <image_name>
• Remove all stopped containers
• docker rm $(docker ps -a -q)
• Remove all noname images
• docker rmi $(docker images -f "dangling=true" -q)
• docker upgrade to CE
• dnf remove docker docker-common docker-selinux docker-engine-selinux docker-engine
• dnf -y install dnf-plugins-core
• dnf config-manager --add-repo https://download.docker.com/linux/fedora/docker-ce.repo
• dnf -y install docker-ce
• add user to docker
• sudo groupadd docker
• sudo gpasswd -a yjpark docker
• sudo usermod -aG yjpark
• docker-compose upgrade
• curl -L https://github.com/docker/compose/releases/download/1.17.0/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose
• replace /usr/bin/docker-compose
• docker registry
• docker pull registry:2
• docker run -d -p 5000:5000 --restart always --name registry registry

vi /etc/docker/daemon.json

{

  "insecure-registries" : ["10.0.0.211:5000"]

}

• push docker
• docker tag docker_test_1 10.0.0.211:5000/docker_test_1
• docker push 10.0.0.211:5000/docker_test_1
• pull docker image from repository
• CE:

vi /etc/docker/daemon.json

{

  "insecure-registries" : ["10.4.38.164:5000"]

}

• Older:

vi /etc/sysconfig/docker

INSECURE_REGISTRY='--insecure-registry 10.4.38.164:5000'

• docker pull 10.4.38.164:5000/utcit-image
• docker tag  10.4.38.164:5000/utcit-image   utcit-image
• lookup
• curl 'http://10.0.0.211:5000/v2/_catalog'
• stop registry
• docker stop registry
• cleanup registry
• docker rm -v registry

• Docker Swarm Cheatsheet

  Cluster Status

  Use the following command to get the status of a cluster. This can only be run from a manager node.

  docker node ls
  
  
  Copy to clipboard
  
  

  
  1. This node is the "primary" manager that actually manages the cluster. The other managers are replicas there for redundancy.
  2. This node is "drained" meaning that it is not running any services, nor will any services be deployed to it in future. This is can be good for managers as it means they are dedicated to managing.
  3. This node is unreachable, meaning it has likely gone offline.
  4. This star indicates the node that you ran the query on.
  You may notice that one of the nodes has a blank under the manager status. This means that it is a worker node and not a manager.

  Node Management

  Add A Node

  When you created the cluster, you should have been given the command that you need to give to other nodes in order to join the cluster. If you don't have this command anymore, you can retrieve it by executing:

  docker swarm join-token worker
  
  
  Copy to clipboard
  
  

  If you want to get the command to join nodes as managers, you can execute:

  docker swarm join-token manager
  
  
  Copy to clipboard
  
  

  The output of both of these commands will be similar to below:

  To add a manager to this swarm, run the following command:
  
      docker swarm join \
      --token SWMTKN-1-154zu01lysyz6qbqxhm5i27b591gg8ffhce2jq438damwelgz6-2qve6pcf9y6j5t3d9dmqnl5kg \
      10.1.0.48:2377
  
  
  Copy to clipboard
  
  

  Scale the service in the swarm Now that you have the relevant command, simply execute it from the node that you wish to have join the swarm. Make sure not to have more than 7 managers, but you can have as many workers as you like.

  Remove A Node

  To gracefully remove a node from a cluster, use the following command on the node itself:

  docker swarm leave
  
  
  Copy to clipboard
  
  

  If the node is currently a manager, you will need to demote it before trying to leave the swarm.
  The node will still show in the list of nodes in the cluster, but its status will be Down and its availability will be Active.
  To now remove the node from the cluster, run the following command on the manager.

  docker node rm $NODE_ID
  
  
  Copy to clipboard
  
  

  Inspect Node

  docker node inspect --pretty $NODE_ID
  
  
  Copy to clipboard
  
  

  Drain Node

  If you want to gracefully remove any containers from a node, and prevent services from running on that node in future then you want to drain it. This could be a useful step to run before updating and rebooting nodes.

  docker node update \
  --availability drain \
  $NODE_ID
  
  
  Copy to clipboard
  
  

  Draining your manager nodes may be a good idea to keep them dedicated to managing the cluster. You may wish to maintain a few tiny, dedicated management nodes for redundancy/reliability and have larger worker nodes for hosting the services.
  To undo this change, execute:

  docker node update --availability active $NODE_ID
  
  
  Copy to clipboard
  
  

  Refer here for more info on draining nodes.

  Demote Node

  To demote a node from a manager to a "follower" node, use the command below:

  docker node demote $NODE_ID
  
  
  Copy to clipboard
  
  

  Promote Node

  To promote a node from a worker to a manager, execute:

  docker node promote $NODE_ID
  
  
  Copy to clipboard
  
  

  Make sure to have an odd number of managers, and no more than 7. All managers should have minimal downtime and have static IPs.

  Services

  To deploy your application to a swarm cluster, you deploy it as a service. By being a service, it has the ability to:
  • be deployed to any of the nodes.
  • be automatically re-deployed if it dies.
  • can be scaled to be run any number of times simultaneously across the cluster.
  • have requests be load-balanced across running containers of the service.

  Create Service

  To deploy your application as a service run:

  docker service create $IMAGE
  
  
  Copy to clipboard
  
  

  Chances are that you probably want to give your service a name to reference it by, and you may want to specify the number of instances/replicas:

  docker service create --name my_web --replicas 3 $IMAGE
  
  
  Copy to clipboard
  
  

  Please refer here for the full list of optional parameters.

  Remove Service

  When you want to remove a service from your cluster, use the following command:

  docker service rm $SERVICE_ID
  
  
  Copy to clipboard
  
  

  List Services

  To see which services are running on your cluster:

  docker service ls
  
  
  Copy to clipboard
  
  

  Scale Service

  If you want to scale up/down after a service has already been deployed...

  docker service scale $SERVICE_ID=$NUM_INSTANCES
  
  
  Copy to clipboard
  
  

  For example

  docker service scale whoami=3
  
  
  Copy to clipboard
  
  

  List Service Processes

  When there are multiple instances of a single service running, you can see them with:

  docker service ps $SERVICE_ID
  
  
  Copy to clipboard
  
  

  This will indicate which nodes the service's containers are running on.

  ID                         NAME          SERVICE     IMAGE   LAST STATE          DESIRED STATE  NODE
  8p1vev3fq5zm0mi8g0as41w35  helloworld.1  helloworld  alpine  Running 7 minutes   Running        worker2
  c7a7tcdq5s0uk3qr88mf8xco6  helloworld.2  helloworld  alpine  Running 24 seconds  Running        worker1
  6crl09vdcalvtfehfh69ogfb1  helloworld.3  helloworld  alpine  Running 24 seconds  Running        worker1
  auky6trawmdlcne8ad8phb0f1  helloworld.4  helloworld  alpine  Running 24 seconds  Accepted       manager1
  ba19kca06l18zujfwxyc5lkyn  helloworld.5  helloworld  alpine  Running 24 seconds  Running        worker2
  
  
  Copy to clipboard
  
  

  Overlay Networks

  Containers deployed on the same overlay network can communicate with each other, even when they are on different nodes. For more information pleas refer here.

  Create Overlay Network

  The command below will create an overlay network called my-network.

  docker network create \
  --driver overlay \
  --subnet 10.0.9.0/24 \
  --opt encrypted \
  my-network
  
  
  Copy to clipboard
  
  

  Remove Overlay Network

  docker network rm $NETWORK_ID
  
  
  Copy to clipboard
  
  

  Deploy Service To Specific Network

  Use the --network [overlay network ID] option when creating a service if you wish to specify which network to join.

  List Networks

  docker network ls
  
  
  Copy to clipboard
  
  

  Example output:

  NETWORK ID          NAME                DRIVER              SCOPE
  a924a6335935        bridge              bridge              local               
  0eb588929cb3        docker_gwbridge     bridge              local               
  6520f47d6e19        host                host                local               
  8puto62h939d        ingress             overlay             swarm               
  064db85ed9e3        none                null                local               
  0fv9x8scsntd        traefik-net         overlay             swarm
  
  
  Copy to clipboard
  
  

  Inspect Network

  docker network inspect $NETWORK_ID
  
  
  Copy to clipboard
  
  

• delete volumes

  // see: https://github.com/chadoe/docker-cleanup-volumes
  
  $ docker volume rm $(docker volume ls -qf dangling=true)
  $ docker volume ls -qf dangling=true | xargs -r docker volume rm
  

  delete networks

  $ docker network ls  
  $ docker network ls | grep "bridge"   
  $ docker network rm $(docker network ls | grep "bridge" | awk '/ / { print $1 }')
  

  remove docker images

  // see: http://stackoverflow.com/questions/32723111/how-to-remove-old-and-unused-docker-images
  
  $ docker images
  $ docker rmi $(docker images --filter "dangling=true" -q --no-trunc)
  
  $ docker images | grep "none"
  $ docker rmi $(docker images | grep "none" | awk '/ / { print $3 }')
  

  remove docker containers

  // see: http://stackoverflow.com/questions/32723111/how-to-remove-old-and-unused-docker-images
  
  $ docker ps
  $ docker ps -a
  $ docker rm $(docker ps -qa --no-trunc --filter "status=exited")
  

  Resize disk space for docker vm

  
  

  $ docker-machine create --driver virtualbox --virtualbox-disk-size "40000" default

• Test swarm:
• Dockerfile

FROM fedora:24

# Clean the new Docker image and update all packages to latest.

RUN dnf clean all

# View and update repositories.

RUN dnf repolist

RUN cat /etc/dnf/dnf.conf

# Install additional packages

RUN dnf install -y tar

RUN dnf install -y python-devel

RUN dnf install -y gcc-c++

RUN dnf install -y make

RUN dnf install -y npm

RUN dnf install -y bzip2

# Install Javascript packages.

RUN npm cache clean -f

RUN npm install n -g

RUN npm install npm@latest -g

RUN n stable

RUN npm install swagger -g

RUN npm install pm2 -g

RUN mkdir /code

WORKDIR /code/

ADD ./ /code/

• docker build -t ci_vote .
• docker tag ci_vote 10.0.0.211:5000/ci_vote
• docker push 10.0.0.211:5000/ci_vote

• docker volume create --name mongoconfig1
• docker volume create --name mongodata1
• docker network create --driver overlay --internal mongo
• docker service create --replicas 1 --detach=false --name mongodb --network mongo --mount type=bind,source=`pwd`/mongodb/db,target=/data/db -p 27017:27017 mongo:latest mongod --smallfiles --logpath=/dev/null # --quiet
• docker service create --replicas 1 --network mongo --mount type=volume,source=mongodata1,target=/data/db --mount type=volume,source=mongoconfig1,target=/data/configdb --constraint 'node.labels.mongo.replica == 1' --name mongo1 --detach=false mongo:3.2 mongod

• git clone https://github.com/kotarac/rockmongo-docker.git
• docker build -t rockmongo .
• docker tag rockmongo 10.0.0.211:5000/rockmongo
• docker push 10.0.0.211:5000/rockmongo

• docker service create --replicas 1 --detach=false --name mongodb --mount type=bind,source=/home/yjpark/perforce/workspace/ci/mongodb/db,target=/data/db --env MONGO_DATA_DIR=/data/db --env MONGO_LOG_DIR=/dev/null -p 27017:27017 mongo:latest mongod --smallfiles --logpath=/dev/null # --quiet
• docker service create --replicas 1 --detach=false --name rockmongo --env MONGO_HOST=10.0.0.211 -p 27018:80 10.0.0.211:5000/rockmongo
• docker service create --replicas 1 --detach=false --name ci_vote --mount type=bind,source=/home/yjpark/perforce/workspace/ci/vote,target=/code:rw -p 9100:9100 10.0.0.211:5000/ci_vote /bin/bash -c "/usr/local/bin/npm install; /usr/local/bin/node app.js"
• docker service create --name=visualizer --publish=8280:8080/tcp --constraint=node.role==manager --mount=type=bind,src=/var/run/docker.sock,dst=/var/run/docker.sock --detach=false dockersamples/visualizer

• Jenkins
• mkdir jenkins
• docker run -p 8080:8080 -p 50000:50000 -v /home/yjpark/perforce/workspace/ci/jenkins:/var/jenkins_home -d --restart always jenkins/jenkins:lts
• 
  

Fedora Commands

• Linux version
• uname -a
• HDD capacity
• df -h
• Memory
• free -m
• Hostname
• vi /etc/hostname
• hostname -F /etc/hostname
• Shell
• cat /etc/shells
• echo $SHELL
• chsh: permanently change shell for user
• Prompt
• export PS1="[\\u@\\h:\\w:]\\$ "
• Size of a directory
• du -sh .
• User
• useradd userid -d <home-dir>
• passwd userid
• userdel -r userid
• /etc/sudoers: add "user_id ALL=(ALL) NOPASSWD: ALL"
• dnf install sudo
• id username
• Reset profile
• dracut --regenerate-all --force
• sync 
• Extend the HDD
• lvextend -l +100%FREE /dev/mapper/fedora-root
• resize2fs /dev/mapper/fedora-root
• Disk image backup & restore: disks and gparted
• Manage start applications
• by gnome-tweak-tool (can be installed in Software)
• Manage services
• systemctl status smb.service
• To show gateway
• ip route show
• nis
• stop & disable firewalld.service
• edit /etc/sysconfig/selinux to disabled 
• dnf install ypbind rpcbind
• /etc/nfsmount.conf
• Defaultvers=3
• ypdomainname hq.k.grp
• /etc/sysconfig/authconfig
• USENIS=yes
• /etc/yp.conf
• domain hq.k.grp server 10.4.50.16
• domain hq.k.grp server 10.4.50.17
• /etc/nsswitch.conf
• passwd: add nis
• shadow: comment out
• group: add nis
• netgroup: nis sss
• automount: files nis sss
• systemctl enable rpcbind ypbind and reboot
• autofs
• dnf install autofs
• /etc/sysconfig/autofs
• BROWSE_MODE="yes"
• /etc/auto.master
• auto.master.mtvlnx
• /etc/resolv.conf
• search hq.k.grp
• nameserver 10.4.40.7
• nameserver 10.4.20.46
• systemctl enable & start autofs.service
• nfs
• NFS mount
• create /mnt/platform
• mount -t nfs 10.73.1.118:/platform /mnt/platform
• vi /etc/fstab
• 10.73.1.118:/platform /mnt/platform nfs defaults 0 0
• With username, password
• mount -t cifs -o username=username,password=password //10.4.38.58/stormtest/flash/build /mnt/stormtest
• vi /etc/fstab
• //10.4.38.58/stormtest/flash/build /mnt/stormtest cifs username=username,password=password 0 0
• NFS export
• /etc/exports
• /home/yjpark *(rw,no_root_squash)
• systemctl start rpcbind nfs-server
• samba
• yum install samba
• system-config-samba or
• vi /etc/samba/smb.conf

     [global]

     workgroup = HQ

     server string = yjpark_linux

          security = user 

          [homes]
          comment = Home Directories
          valid users = %S, %D%w%S
          browseable = Yes
          writable = yes
          inherit acls = Yes

     [yjpark] => doesn't seem to need it

     comment = Yongjin's linux PC

     path = /local/yjpark

     public = yes

     writable = yes

          browseable = Yes

• service smb restart
• smbpasswd -a yjpark
• firewall-cmd --permanent --add-service=samba
• service firewalld restart
• http
• systemctl enable/start httpd.service
• telnet
• yum install telnet-server
• systemctl start telnet.socket or systemctl enable telnet.socket
• firewall-cmd --permanent --add-service=telnet
• service firewalld restart
• ftp
• yum install vsftpd
• /etc/vsftpd/vsftpd.conf

         local_enable=yes

• service vsftpd start
• tftp
• dnf install tftp-server
• systemctl enable & start tftp.socket
• cd /; ln -s /var/lib/tftpboot
• change home: /lib/systemd/system/tftp.service
• libs
• dnf
• sudo, procps, passwd, python-devel, libxslt-devel, libxml2-devel, redhat-rpm-config, python-pip, pandoc, nodejs, npm, daemonize, libXScrnSaver, libXScrnSaver-devel, GConf2, fontconfig, cairo, cairo-devel, cairomm-devel, libjpeg-turbo-devel, pango, pango-devel, pangomm, pangomm-devel, giflib-devel, libXi, libXcursor
• pip
• --upgrade pip, lxml, beautifulsoup4, junit_xml
• npm
• npm@latest -g, selenium-webdriver -g, selenium-webdriver (as localadmin)
• OTV5-CI docker node setup:
• create /home/jk for localadmin:localadmin
• cp /users/yjpark/p4/p4 to /usr/local/bin
• dnf update
• dnf install docker, enable & start
• docker load -i /users/yjpark/docker/*
• pip install --upgrade pip, lxml, bs4, junit_xml
• firewall
• firewall-cmd --add-port=80/tcp --permanent
• firewall-cmd --reload
• service firewalld stop
• query service ports
• vi /etc/services
• or sudo nmap -sT -O localhost
• or netstat -anp
• Apach2
• dnf install httpd
• version: httpd -v
• systemctl start httpd.service
• default index file: touch /var/www/html/index.html
• PHP
• dnf install php
• image handling module: dnf install php-gd
• multi language: dnf install php-mbstring
• MySQL
• dnf install mariadb
• dnf install mariadb-server
• systemcdtl start mariadb.service
• /usr/bin/mysql_secure_installation
• Setup root password, etc
• dnf install php-mysql (FC24)
• dnf install php-pdo_mysql (FC25)
• dnf install MySQL-python
• vi /etc/my.cnf

         [mysqld]

                :

         character-set-server = utf8mb4

         collation-server = utf8mb4_unicode_ci

• systemctl restart mariadb.service
• mkdir www
• exit
• phpMyAdmin
• dnf install phpmyadmin
• vi /etc/httpd/conf.d/phpMyAdmin.conf

   AddDefaultCharset UTF-8

   <IfModule mod_authz_core.c>

     # Apache 2.4

     <RequireAny>

       #ADD following line:

       Require all granted

       Require ip 127.0.0.1

       Require ip ::1

     </RequireAny>

   </IfModule>

   <IfModule !mod_authz_core.c>

     # Apache 2.2

     #CHANGE following 2 lines:

     Order Allow,Deny

     Allow from All

     Allow from 127.0.0.1

     Allow from ::1

   </IfModule>

</Directory>

• ffmpeg
• rpm -Uvh http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-stable.noarch.rpm
• In case need GPG key:
• https://rpmfusion.org/keys?action=AttachFile&do=view&target=RPM-GPG-KEY-rpmfusion-free-fedora-20
• sudo rpm --import key_above
• dnf install ffmpeg
• nginx
• dnf install nginx
• systemctl enable nginx
• vi /etc/nginx/nginx.conf:

          listen 8090 default_server;

          root /home/yjpark/www

• semanage port -l | grep http_port_t
• semanage port -a -t http_port_t -p tcp 8090
• systemctl start nginx
• getenforce
• setenforce Permissive
• systemctl stop nginx; systemctl start nginx
• chcon -Rt httpd_sys_content_t /home/yjpark/perforce/workspace/www/nginx
• nginx: install from source
• openssl:
• wget http://www.openssl.org/source/openssl-1.0.2f.tar.gz
• cd openssl-1.0.2f
• ./Configure linux-x86_64 --prefix=/usr
• make; sudo make install
• pcre
• wget ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/pcre-8.40.tar.gz
• ./configure; make; sudo make install
• wget http://zlib.net/zlib-1.2.11.tar.gz
• ./configure; make; sudo make install
• download https://github.com/arut/nginx-rtmp-module
• wget http://nginx.org/download/nginx-1.11.9.tar.gz
• ./configure --add-module=../nginx-rtmp-module-master --with-http_ssl_module
• make; sudo make install
•   mkdir /tmp/HLS/cam
• In /usr/local/nginx/conf/nginx.conf:

rtmp {

    server {

        listen 1935;

        allow play all;

        chunk_size 4000;

        # video on demand for flv files

        application cam {

            allow play all;

            live on;

            hls on;

            hls_nested on;

            hls_path /tmp/HLS/cam;

            hls_fragment 10s;

            exec_static ffmpeg -i rtmps://stream-delta.dropcam.com/nexus/a203d89605a4454a94caed1b16024f79 -c:v libx264 -an -f flv rtmp://localhost:1935/cam/nest;
            exec_static ffmpeg -i rtmps://stream-delta.dropcam.com/nexus/a203d89605a4454a94caed1b16024f79 -g 1 -s 320x240 -vcodec libx264 -vprofile baseline -acodec libmp3lame -ar 44100 -ac 1 -f flv rtmp://localhost:1935/cam/nest;

        }

        # video on demand for mp4 files

        application vod {

            allow play all;

            play /home/yjpark/www/nginx/mp4s;

        }

        application hls {

            live on;

            hls on;

            hls_path /tmp/HLS;

        }

    }

}

http {

    include       mime.types;

    default_type  application/octet-stream;

    #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '

    #                  '$status $body_bytes_sent "$http_referer" '

    #                  '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  logs/access.log  main;

    sendfile        on;

    #tcp_nopush     on;

    #keepalive_timeout  0;

    keepalive_timeout  65;

    #gzip  on;

    server {

        listen       8090;

        server_name  localhost;

        #charset koi8-r;

        #access_log  logs/host.access.log  main;

        location / {

            root /home/yjpark/www/nginx/html;

            index index.html index.htm;

        }

        #creates the http-location for our full-resolution (desktop) HLS stream - "http://my-ip/cam/nest/index.m3u8"

        location /cam {

            types {

                application/vnd.apple.mpegurl m3u8;

                video/mp2t ts;

            }

            alias /tmp/HLS/cam;

            add_header Cache-Control no-cache;

        }

        #error_page  404              /404.html;

        # redirect server error pages to the static page /50x.html

        #

        error_page   500 502 503 504  /50x.html;

        location = /50x.html {

            root   html;

        }

        # proxy the PHP scripts to Apache listening on 127.0.0.1:80

        #

        #location ~ \.php$ {

        #    proxy_pass   http://127.0.0.1;

        #}

        # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000

        #

        #location ~ \.php$ {

        #    root           html;

        #    fastcgi_pass   127.0.0.1:9000;

        #    fastcgi_index  index.php;

        #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;

        #    include        fastcgi_params;

        #}

        # deny access to .htaccess files, if Apache's document root

        # concurs with nginx's one

        #

        #location ~ /\.ht {

        #    deny  all;

        #}

    }

}

• sudo /usr/local/nginx/sbin/nginx -s stop;  sudo /usr/local/nginx/sbin/nginx

• Server/client certificates
• http://theheat.dk/blog/?p=1023
• https://engineering.circle.com/https-authorized-certs-with-node-js-315e548354a2
• Perforce
• Download p4d from https://www.perforce.com/downloads/helix-versioning-engine-p4d
• vi /etc/systemd/system/p4d.service

• # Example Perforce systemd file (p4d.service):
  #
  # This service file will start Perforce at boot, and
  # provide everything needed to use systemctl to control
  # the Perforce server process.
  
  [Unit]
  # Note that descriptions are limited to 80 characters:
  Description=Perforce Server
  
  # Starts Perforce only after the network services are 
  # ready:
  #After=network.target
  After=network-online.target
  
  [Service]
  # The type should always be set to "forking" to support
  # multiple Perforce processes:
  Type=forking
  
  # Set the system user used to launch this process (usually
  # 'perforce':
  User=perforce
  
  # The command used to start Perforce:
  ExecStart=/usr/bin/p4d -r /home/yjpark/p4d/p4d -p 10.0.0.211:1666 -d
  
  [Install]
  # Describes the target for this service -- this will always
  # be 'multi-user.target':
  WantedBy=multi-user.target

• service start p4d
• service enable p4d
• a symbolic link to p4d.service file will be created in /etc/systemd/system/multi-user.target.wants
• Download p4v from https://www.perforce.com/downloads/helix-visual-client-p4v
• dual boot order
• /etc/default/grub
• change GRUB_DEFAULT=<number>
• grub2-mkconfig -o /boot/grub2/grub.cfg
•   Nomachine for Fedora 26+
• Until we add support for Wayland protocol you should disable Wayland in the gdm configuration by adding the following key in /etc/gdm/custom.conf:
• WaylandEnable=false
•