Mobile

Converting Android Device Into Linux Server¶

Centos¶

1. Pre-requisites

   • Identify an Android mobile phone
   • Factory reset to remove any unwanted apps and data
   • Remove any apps or services from the device to free up space and memory
   • Install Termux and AnLinux from Playstore

2. Installation

   • Start AnLinux and search for the distro. Select Centos
   • Copy the installation command
   • Open Termux terminal and paste the command
   • Begin installation

3. Access Mobile

   • Configure Static Ip to Mobile
   • Add Ip address and remote-hostname to Laptop's hosts file.
   • Install SSH on Termux apt install openssh
   • Start the ssh server sshd. This will also generate the private and public keys.
   • Test the service locally ssh localhost -p 8022. Accept the public key.
   • ssh-copy-id copies the local-host’s public key to the remote-host’s authorized_keys file. ssh-copy-id -i ~/.ssh/id_rsa.pub <remote-hostname> -p 8022. Enter remote user password to complete transaction.
   • Login from Laptop ssh <hostname> -p 8022. Enter the passphrase.
   • Install Python

4. Configuring Centos

   • Update Centos with latest patches yum install update -y && yum install upgrade -y
   • Verify the OS Version cat /etc/os-releases
   • net-tools package provides the ifconfig command yum install net-tools -y
   • Init Centos yum -y install initscripts & yum clean all
   • Change Root Password passwd root
   • Install Sudo yum install sudo -y
   • The difference between wheel and sudo.

   In CentOS, a user belonging to the wheel group can execute su and directly ascend to root. Meanwhile, a sudo user would have use the sudo su first. Essentially, there is no real difference except for the syntax used to become root, and users belonging to both groups can use the sudo command. *

   Adding Non Root User

   • bmmnb

   Add and Delete Users

5. Securing Server

   Security based on articles mentioned here or here or DigitalOcean

   Configures a Hostname Reconfigures the Timezone Updates the entire System Creates a New Admin user so you can manage your server safely without the need of doing remote connections with root. Helps user Generate Secure RSA Keys, so that remote access to your server is done exclusive from your local pc and no Conventional password Configures, Optimize and secures the SSH Server (Some Settings Following CIS Benchmark) Configures IPTABLES Rules to protect the server from common attacks Disables unused FileSystems and Network protocols Protects the server against Brute Force attacks by installing a configuring fail2ban Installs and Configure Artillery as a Honeypot, Monitoring, Blocking and Alerting tool Installs PortSentry Installs RootKit Hunter Secures Root Home and Grub Configuration Files Installs Unhide to help Detect Malicious Hidden Processes Installs Tiger, A Security Auditing and Intrusion Prevention system Restrict Access to Apache Config Files Disables Compilers Creates Daily Cron job for System Updates Kernel Hardening via sysctl configuration File (Tweaked) /tmp Directory Hardening PSAD IDS installation Enables Process Accounting Enables Unattended Upgrades MOTD and Banners for Unauthorized access Disables USB Support for Improved Security (Optional) Configures a Restrictive Default UMASK Configures and enables Auditd Configures Auditd rules following CIS Benchmark Sysstat install ArpWatch install Additional Hardening steps following CIS Benchmark Secures Cron Automates the process of setting a GRUB Bootloader Password Secures Boot Settings Sets Secure File Permissions for Critical System Files