blxrep

blxrep is a powerful tool designed for live data replication of disks over a network. It operates in two modes: dispatcher and agent, allowing for efficient and flexible disaster recovery setup. blxrep tracks the changes that happen on disk at sector level using eBPF tracepoints.

Table of Contents

• Overview
• Installation
• Configuration
• Usage
  • Starting blxrep
  • Dispatcher Commands
• Modes of Operation
• TUI mode

Overview

Traditionally, companies have relied on kernel modules for change block tracking and bitmap-based incremental backups. While functional, this approach has several limitations:

1. Complex kernel module development and maintenance requiring deep kernel expertise
2. Challenging debugging process due to kernel space operations
3. Limited testing capabilities in kernel space
4. Scalability constraints due to kernel-level implementation
5. Steep learning curve for kernel module development
6. System reboots required for kernel module loading and updates
7. Potential for system instability and security vulnerabilities due to unrestricted kernel access

blxrep modernizes this approach by leveraging eBPF tracepoints to track disk changes at the sector level. This brings several advantages:

1. Simplified development through eBPF's modern tooling, extensive documentation, and active community support
2. Enhanced debugging capabilities with user-space tools and eBPF maps
3. Comprehensive testing framework support
4. Better scalability through efficient event processing
5. More approachable learning curve with high-level eBPF programming interfaces
6. Dynamic loading without system reboots
7. Improved safety through eBPF's verifier and sandboxed execution environment

Installation

For Debian/Ubuntu based systems (.deb)

1. Download the package:

wget https://github.com/xmigrate/blxrep/releases/download/v0.1.0/blxrep-0.1.0-amd64.deb

2. Install the package:

sudo dpkg -i blxrep-0.1.0-amd64.deb

Note: If you get an error about missing dependencies, you can install them with:

sudo apt-get install -f

For Redhat/CentOS based systems (.rpm)

1. Download the package:

wget https://github.com/xmigrate/blxrep/releases/download/v0.1.0/blxrep-0.1.0-x86_64.rpm

2. Install the package:

sudo rpm -i blxrep-0.1.0-x86_64.rpm

Verify the installation:

sudo blxrep --help

Configuration file is located at /etc/blxrep/config.yaml by default. Policy directory is located at /etc/blxrep/policies by default.

Policy Configuration

Default Policy configuration is located at /etc/blxrep/policies/default.yaml by default.

name: "default-backup-policy" # name of the policy
description: "Backup policy for all servers" # description of the policy
archive_interval: 48h # archive interval
snapshot_frequency: "daily" # snapshot frequency
snapshot_time: "12:00" # snapshot time
bandwidth_limit: 100 # bandwidth limit
snapshot_retention: 30 # snapshot retention
live_sync_frequency: 2m # live sync frequency
transition_after_days: 30 # transition after days
delete_after_days: 90 # delete after days

targets:
  # Range pattern
  - pattern: "*" # pattern of the targets which is mentioned on agent /etc/blxrep/config.yaml
    disks_excluded: 
      - "/dev/xvda" # disks excluded from the policy

You can create your own policy by creating a new yaml file in the /etc/blxrep/policies directory.

Post Installation

After installation, enable and start the blxrep service:

sudo systemctl enable blxrep
sudo systemctl start blxrep

After starting the blxrep service, you can see the status of the blxrep service with the following command:

sudo systemctl status blxrep

Uninstallation

To uninstall blxrep, use the following command:

For Debian/Ubuntu:

sudo dpkg -r blxrep

For Redhat/CentOS:

sudo rpm -e blxrep

Configuration

blxrep uses a configuration file located at /etc/blxrep/config.yaml by default. You can specify a different configuration file using the --config flag.

Example configuration for agent:

mode: "agent"
id: "hostname"
dispatcher-addr: "localhost:8080"
data-dir: "/data"

Example configuration for dispatcher:

mode: "dispatcher"
data-dir: "/data"
policy-dir: "/etc/blxrep/policies"

Usage

Starting blxrep

To start blxrep, use the start command:

blxrep start [flags]

Flags:

Flag	Description	Required For
--mode	Start mode ('dispatcher' or 'agent')	Both
--id	Agent ID	Agent mode
--dispatcher-addr	Dispatcher address (format: host:port)	Agent mode
--data-dir	Data directory	Dispatcher mode
--policy-dir	Policy directory	Dispatcher mode
--config	Configuration file	Optional

Modes of Operation

Dispatcher Mode

In dispatcher mode, blxrep manages the overall replication process. It acts as a central collector for replicating disk data from multiple servers. It requires a data directory and policy directory to be specified. All types of disk backups are collected and stored in the specified data directory. Policy directory is used to specify the policy for the disk backups for each agent.

Agent Mode

In agent mode, blxrep runs on individual servers to send snapshot backups and live changes to the dispatcher. It requires an agent ID, dispatcher address, and device to be specified. We need the agent ID to be unique if we are connecting multiple servers to the same dispatcher. Device is the disk that needs to be backed up and monitored for live changes.

TUI mode

blxrep uses tcell for the TUI. It is a terminal UI library for Go that is easy to use and highly customizable. It is used to interact with the dispatcher and agents. With TUI mode, you can navigate throught the agegnts that are connected to the dispatcher and see the status of the disk backups. You can also mount the disk backups to any available point in time and restore the files or partitions with the help of the TUI.

To start the TUI, use the tui command:

blxrep tui --data-dir=<data_directory>