Increases swap in azure linux machine

In Azure to create a swap file in the directory that's defined by the ResourceDisk.MountPoint parameter, you can update the /etc/waagent.conf file by setting the following three parameters:

ResourceDisk.Format=y
ResourceDisk.EnableSwap=y
ResourceDisk.SwapSizeMB=xx

Note The xx placeholder represents the desired number of megabytes (MB) for the swap file.
Restart the WALinuxAgent service by running one of the following commands, depending on the system in question:

Ubuntu: service walinuxagent restart
Red Hat/Centos: service waagent restart

Run one of the following commands to show the new swap apace that's being used after the restart:

dmesg | grep swap
swapon -s
cat /proc/swaps
file /mnt/resource/swapfile
free| grep -i swap

If the swap file isn't created, you can restart the virtual machine by using one of the following commands:

shutdown -r now
init 6

Docker Clustering with Swarm in Centos7

Docker Clustering with Swarm in Centos7 is a process of creating a cluster of Docker hosts using the Docker Swarm feature in the CentOS 7 operating system. The Swarm feature is a native clustering and orchestration tool within Docker that enables users to create and manage a cluster of Docker hosts. This process involves setting up a Docker Swarm manager and one or more Docker Swarm nodes, configuring the network and storage for the cluster, and deploying and scaling Docker services across the cluster. The benefits of clustering Docker hosts with Swarm in CentOS 7 include increased scalability, high availability, and load balancing of Docker services, as well as simplified management and deployment of containerized applications.

Installing Docker

mkdir /install-files ; cd /install-files

wget https://yum.dockerproject.org/repo/main/centos/7/Packages/docker-engine-1.13.1-1.el7.centos.x86_64.rpm
wget https://yum.dockerproject.org/repo/main/centos/7/Packages/docker-engine-selinux-1.13.1-1.el7.centos.noarch.rpm

Package for docker-engine-selinux

yum install -y policycoreutils-python
rpm -i docker-engine-selinux-1.13.1-1.el7.centos.noarch.rpm

Package for docker-engine

yum install -y libtool-ltdl libseccomp
rpm -i docker-engine-1.13.1-1.el7.centos.x86_64.rpm

Remove rpm packages

rm docker-engine-* -f

Enable systemd service

systemctl enable docker

Start docker

systemctl start docker

Firewalld Enabling Firewall Rules

firewall-cmd --get-active-zones
firewall-cmd --list-all
firewall-cmd --zone=public --add-port=2377/tcp --permanent
firewall-cmd --permanent --add-source=192.168.56.0/24
firewall-cmd --permanent --add-port=2377/tcp
firewall-cmd --permanent --add-port=7946/tcp
firewall-cmd --permanent --add-port=7946/udp
firewall-cmd --permanent --add-port=4789/udp
firewall-cmd --reload

Enable and Restart systemd service

systemctl enable docker;
systemctl restart docker

Docker Cluster Env

docker swarm init --advertise-addr=192.168.56.105

Swarm initialized: current node (b4b79zi3t1mq1572r0iubxdhc) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join \
    --token SWMTKN-1-1wcz7xfyvhewvj3dd4wcbhufw4lub3b1vgpuoybh90myzookbf-4ksxoxrilifb2tmvuligp9krs \
    192.168.56.101:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

To join as a Swarm manager

docker swarm join-token manager

  docker swarm join \
    --token SWMTKN-1-10cqx6yryq5kyfe128m2xhyxzplsc90lzksqggmscv1nfipsbb-bfdbvfhuw9sg8mx2i1a4rkvlv \
    192.168.56.101:2377

Creating CSR with multiple Domains With Openssl

Creating a CSR (Certificate Signing Request) with multiple domains using OpenSSL involves generating a private key and a CSR file, which includes the details of the domain(s) to be included in the certificate. The process involves the following steps:

Generate a private key using the openssl command with the following syntax:

openssl genrsa -out domain.key 2048

This generates a private key file named "domain.key" with 2048 bits of encryption.

Create a configuration file (e.g. domain.conf) that contains the details of the domains to be included in the certificate. This file should contain the following details:

[req]

default_bits       = 2048

default_keyfile    = domain.key

distinguished_name = req_distinguished_name

req_extensions     = req_ext

[req_distinguished_name]

countryName             = Country Name (2 letter code)

stateOrProvinceName     = State or Province Name (full name)

localityName            = Locality Name (eg, city)

organizationName        = Organization Name (eg, company)

commonName              = Common Name (e.g. server FQDN or YOUR name)

emailAddress            = Email Address

[req_ext]

subjectAltName          = @alt_names

[alt_names]

DNS.1                  = example.com

DNS.2                  = www.example.com

DNS.3                  = subdomain.example.com

In the example above, "example.com", "www.example.com", and "subdomain.example.com" are included as the alternate domain names.

Generate a CSR file using the openssl command with the following syntax:

openssl req -new -sha256 -key domain.key -out domain.csr -config domain.conf

This generates a CSR file named "domain.csr" that contains the details of the private key and the alternate domain names specified in the configuration file.

Submit the CSR file to a Certificate Authority (CA) to obtain a signed SSL certificate that can be installed on the server.

Overall, this process allows for the creation of a CSR file with multiple domain names that can be used to obtain a signed SSL certificate to secure those domains.