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thimslugga/hashicorp_nomad_single_node.md

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Nomad Single Node Deployment
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hashicorp_nomad_single_node.md

Hashicorp Nomad (Single Node Deployment)

Overview

Nomad is designed to be a highly-available, quorum-based cluster scheduler. Nomad deployments should ideally have three or more server nodes and one or more client nodes.

However, Nomad does provide a mode, which you can use to run Nomad with a single agent process.

Note: Nomad dev agents do behave slightly different than non-dev agents. To create a more authentic feeling experience, you might want to run Nomad with a configuration that runs both the client and server processes.

This configuration will enable you to run a single-node Nomad "cluster".

Running Nomad in this configuration comes with several tradeoffs and caveats.

For Example:

  • The node has zero high availability -- the main drive for a scheduler.
  • If the state is damaged, you will have to wipe it and start over.
  • If your IP address changes, you have to perform peers.json recovery or wipe the state.
  • You can't run more than one instance of a workload that uses static ports.

Setup

cat <<EOF >> /etc/hosts

172.25.100.50 nomad-master
172.25.100.51 nomad-minion

EOF

echo "49152 65535" > /proc/sys/net/ipv4/ip_local_port_range

echo 1 > /proc/sys/net/bridge/bridge-nf-call-arptables
echo 1 > /proc/sys/net/bridge/bridge-nf-call-ip6tables
echo 1 > /proc/sys/net/bridge/bridge-nf-call-iptables

cat <<EOF > /etc/sysctl.d/98-hashicorp-nomad.conf
net.bridge.bridge-nf-call-arptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1

EOF

sysctl --system

cat /proc/sys/net/ipv4/ip_local_port_range

Create the nomad user and necessary directories

mkdir -p /opt/cni/bin
mkdir -p /opt/nomad/{plugins,data}

mkdir -p /etc/nomad.d
chmod 700 /etc/nomad.d
touch /etc/nomad.d/{nomad,server,client}.hcl

groupadd -r nomad
useradd --system --home /etc/nomad.d -s /bin/false nomad
#useradd -Mr -g nomad -s /usr/sbin/nologin nomad

Ubuntu:

apt-get update \
  && apt-get upgrade -y
  
sudo apt-get install -y \
    ca-certificates \
    curl \
    wget \
    gnupg \
    lsb-release \
    git \
    ufw \
    seccomp \
    jq \
    unzip \
    vim

Ubuntu repos:

#curl -fsSL https://apt.releases.hashicorp.com/gpg | apt-key add -
apt-add-repository "deb [arch=amd64] https://apt.releases.hashicorp.com $(lsb_release -cs) main"

apt-get update \
  && apt-get install -y nomad

RHEL based systems:

yum update

yum install -y \
  yum-utils \
  curl \
  wget \
  jq \
  unzip \
  firewald \
  vim \
  git

Repos for RHEL based systems:

yum-config-manager --add-repo https://rpm.releases.hashicorp.com/RHEL/hashicorp.repo

yum update \
  && yum -y install nomad

Manually download binaries:

export NOMAD_VERSION="1.1.0"

curl -sL --remote-name 'https://releases.hashicorp.com/nomad/${NOMAD_VERSION}/nomad_${NOMAD_VERSION}_linux_amd64.zip' \
  -o nomad_linux_amd64.zip
  
unzip nomad_linux_amd64.zip

sudo chown root:root nomad
sudo mv nomad /usr/local/bin/

nomad version
#nomad -v

nomad -autocomplete-install
complete -C /usr/local/bin/nomad nomad

nomad podman driver

curl -sL https://releases.hashicorp.com/nomad-driver-podman/0.5.1/nomad-driver-podman_0.5.1_linux_amd64.zip \
  nomad-driver-podman_linux_amd64.zip
unzip nomad-driver-podman_linux_amd64.zip

#mv nomad-driver-podman /var/nomad/plugins/
mv nomad-driver-podman /opt/nomad/plugins/

cni driver:


curl -sL -o cni-plugins.tgz https://github.com/containernetworking/plugins/releases/download/v1.3.0/cni-plugins-linux-amd64-v1.3.0.tgz
tar -C /opt/cni/bin -xzf cni-plugins.tgz

Ubuntu firewall

ufw allow 4646:4647/tcp
ufw allow 4648
ufw reload
ufw status verbose

RHEL based host firewall:

sudo firewall-cmd --permanent --zone=public --add-port=4646/tcp --add-port=4647/tcp  --add-port=4648/tcp  --add-port=4648/udp
sudo firewall-cmd --reload
sudo firewall-cmd --zone=public --list-ports

Systemd service:

cat <<EOF > /etc/systemd/system/nomad.service
[Unit]
Description=Nomad
Documentation=https://www.nomadproject.io/docs/
Wants=network-online.target
After=network-online.target

# When using Nomad with Consul it is not necessary to start Consul first. These
# lines start Consul before Nomad as an optimization to avoid Nomad logging
# that Consul is unavailable at startup.
#Wants=consul.service
#After=consul.service

[Service]

# Nomad server should be run as the nomad user. Nomad clients
# should be run as root
User=nomad
Group=nomad

ExecReload=/bin/kill -HUP $MAINPID
ExecStart=/usr/local/bin/nomad agent -config /etc/nomad.d
KillMode=process
KillSignal=SIGINT
LimitNOFILE=65536
LimitNPROC=infinity
Restart=on-failure
RestartSec=2

## Configure unit start rate limiting. Units which are started more than
## *burst* times within an *interval* time span are not permitted to start any
## more. Use `StartLimitIntervalSec` or `StartLimitInterval` (depending on
## systemd version) to configure the checking interval and `StartLimitBurst`
## to configure how many starts per interval are allowed. The values in the
## commented lines are defaults.

# StartLimitBurst = 5

## StartLimitIntervalSec is used for systemd versions >= 230
# StartLimitIntervalSec = 10s

## StartLimitInterval is used for systemd versions < 230
# StartLimitInterval = 10s

TasksMax=infinity
OOMScoreAdjust=-1000

[Install]
WantedBy=multi-user.target
EOF

Nomad agent configuration, start Nomad with nomad agent -config=/etc/nomad.d.

cat <<EOF > /etc/nomad.d/nomad.conf
FLAGS=-bind 0.0.0.0 -dev
EOF

cat <<EOF > /etc/nomad.d/nomad.hcl
## https://www.nomadproject.io/docs/agent/configuration

datacenter = "iad1"

#name = "nomad-master"

bind_addr = "0.0.0.0"

data_dir = "/opt/nomad/data"
plugin_dir = "/opt/nomad/plugins"

disable_update_check = true

leave_on_interrupt = true
leave_on_terminate = true 

## https://www.nomadproject.io/docs/agent/configuration/index.html#log_level
## [WARN|INFO|DEBUG]
log_level = "INFO"
#enable_syslog = true 
#log_file = "/var/log/nomad.log"
#log_rotate_bytes = 10485760
#log_rotate_max_files = 5

#addresses {
#  http = "0.0.0.0"
#}

#server {
#  enabled = true
#  bootstrap_expect = 1
#}

#client {
#  enabled = true
#  servers = ["127.0.0.1"]
#}

#acl {
#  enabled = true
#}

#ui {
#  enabled = false
#}

EOF

Server

cat <<EOF > /etc/nomad.d/server.hcl
server {
  enabled = true
  bootstrap_expect = 1
  #encrypt = "<nomad_key>"

  #server_join {
    #retry_join = ["<server_ip>"]
    #retry_max  = 0
}

EOF

Client

cat <<EOF > /etc/nomad.d/client.hcl
client {
  enabled = true
  servers = ["127.0.0.1"]
  #servers = ["nomad-master"]
}

#plugin "nomad-driver-podman" {
#    config {
#        socket_path = "unix:///var/run/podman.sock"
#    }
#}

EOF

Enable and start the systemd service:

systemctl unmask nomad
systemctl enable --now nomad
systemctl status nomad

Verify:

nomad server members
nomad server members -detailed
nomad node status
nomad agent-info

Admin tasks

nomad monitor
nomad node eligibility -disable {node-id}
nomad node drain -enable {node-id}

nomad job init

vim example.nomad

cat <<EOF > redis.nomad
job "redis" {
  datacenters = ["iad1"]
  group "cache" {
    network {
      port "redis" { to = "6379" }
    }
  task "redis" {
      driver = "podman"
      config {
        image = "redis:6.2"
        ports = ["redis"]
      }
      resources {
        cpu    = 500
        memory = 256
      }
    }
  }
}

EOF

cat <<EOF > http-echo.nomad
job "http-echo" {
  datacenters = ["iad1"]
  group "echo" {
    network {
      mode = "bridge" 
      port "http" {
        static = 8080
        to = 80
      }
    }
    count = 2
    task "server" {
      driver = "docker"
      config {
        image = "nginx"
        ports = ["http"]
      }
    }
  }
}

EOF

nomad job run example.nomad
nomad status example

nomad alloc status <allocation_id>
nomad alloc logs <allocation_id> redis

nomad job plan example.nomad

nomad job stop example
nomad job status example
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