snap-slack

Snap-Slack: Btrfs Snapshot Manager with Elilo Bootloader Integration

Snap-Slack is a Python-based utility for managing Btrfs snapshots on Slackware Linux. It provides functionality to create snapshots, manage existing snapshots, clean up old snapshots, and adopt snapshots as the new root subvolume. The tool also integrates with the Elilo bootloader, updating the configuration automatically to include snapshots.

Features

• Create Btrfs snapshots before system upgrades or custom tasks
• List snapshots with creation date and age information
• Manage snapshots by removing old ones based on retention policy
• Boot into snapshots directly from the Elilo bootloader menu
• Adopt a snapshot as the new root subvolume, allowing easy rollback
• Verify system configuration to ensure proper setup
• Detailed logging for troubleshooting
• Automatic recovery in case of errors during critical operations

Prerequisites

• Python 3.x
• Btrfs installed and set up on your root filesystem
• Elilo bootloader configured on your system
• toml Python package (for configuration file parsing)
• Slackware or Slackware-based system

Installation

From SlackBuild

1. Download the snap-slack.SlackBuild script and associated files

2. Run the SlackBuild script:

   ./snap-slack.SlackBuild
   

3. Install the package:

   sudo installpkg /tmp/snap-slack-2.0-x86_64-1_SBo.txz
   

This will install the script to /usr/bin/snap-slack and place the configuration file at /etc/snap-slack/config.toml.

Configuration

The script reads its configuration from /etc/snap-slack/config.toml. You should edit this file to match your system's settings before using snap-slack.

Here is an explanation of the configuration parameters:

[snapshot] Section

• snapshot_dir: Directory where Btrfs snapshots are stored (e.g., /.snapshots)
• snapshot_prefix: Prefix for snapshot names (e.g., snapshot-)
• btrfs_mount_point: Mount point for the Btrfs volume (usually /)
• root_subvolume: Name of the current root subvolume (usually @ in Slackware)
• retention_days: Number of days to retain snapshots before automatic deletion

[bootloader] Section

• type: Specify either elilo or grub depending on your system's bootloader

[elilo] Section (when using ELILO bootloader)

• elilo_conf: Path to elilo.conf (e.g., /boot/efi/EFI/Slackware/elilo.conf)
• root_partition: Device name for the root partition (e.g., /dev/sda2)
• extra_boot_options: Additional kernel parameters (e.g., quiet splash)

[grub] Section (when using GRUB bootloader)

• use_custom_file: Set to true to use a custom file in /etc/grub.d/ (recommended)
• custom_entries_file: Path to the custom file (e.g., /etc/grub.d/60_snap-slack)
• config_file: Path to GRUB configuration file (e.g., /boot/grub/grub.cfg)
• root_partition: Device name for the root partition (e.g., /dev/sda2)
• kernel_path: Path to the kernel image (e.g., /boot/vmlinuz)
• initrd_path: Path to the initrd image (e.g., /boot/initrd.gz)
• extra_boot_options: Additional kernel parameters (e.g., quiet splash)

[boot] Section

• boot_dir: Path to the boot directory (e.g., /boot)
• hostname: System hostname (used for snapshot descriptions)

Usage

Once installed and configured, you can use the snap-slack command to manage Btrfs snapshots and integrate them with Elilo.

Verify System Configuration

Before using snap-slack, verify that your system is properly configured:

snap-slack verify

This will check that your system has Btrfs installed, the root filesystem is Btrfs, and other necessary prerequisites are met.

Create a Snapshot

To create a new Btrfs snapshot of the root subvolume:

snap-slack create

The script will:

• Create a new read-only snapshot with a timestamp
• Add the snapshot to the elilo.conf bootloader configuration

List Snapshots

To list all existing snapshots with details:

snap-slack list

This will display a table of all snapshots, their creation dates, and ages.

Manage Snapshots

To manage existing snapshots (clean up old snapshots and update elilo.conf):

snap-slack manage

This will:

• Remove snapshots older than the retention period specified in the configuration
• Ensure that elilo.conf has entries for all valid snapshots

Configure a Snapshot for Booting

To configure a specific snapshot for booting:

snap-slack boot --snapshot snapshot-20240424-123456

This will ensure that the snapshot is properly configured in elilo.conf for booting.

Adopt a Snapshot as the New Root Subvolume

If you want to adopt a specific snapshot as the new root subvolume (rollback to a previous state):

snap-slack adopt --snapshot snapshot-20240424-123456

This will:

• Create a backup of the current root subvolume
• Delete the current root subvolume
• Create a new root subvolume based on the selected snapshot
• Provide instructions for booting into the new root filesystem

Recovery Process

Booting into a Snapshot

When you want to boot into a snapshot to test it before adoption:

1. Create or select a snapshot: snap-slack list
2. Configure it for booting: snap-slack boot --snapshot <snapshot-name>
3. Reboot your system
4. In the ELILO boot menu, select the entry with the snapshot name
5. Test the system

Rolling Back to a Snapshot

If you want to permanently make a snapshot your new root filesystem:

1. Boot into your normal system (not the snapshot)
2. Run: snap-slack adopt --snapshot <snapshot-name>
3. Reboot
4. The system will now boot with the adopted snapshot as the root filesystem

Emergency Recovery

If something goes wrong during the adoption process:

1. Reboot your system
2. In the ELILO bootloader menu, select any working snapshot
3. After booting, you can attempt the adoption process again or troubleshoot the issue

Advanced Usage Scenarios

Creating a Snapshot Before System Upgrade

# Create a snapshot before upgrading
snap-slack create
# Perform your upgrade
slackpkg update
slackpkg upgrade-all

Creating a Weekly Snapshot with Cron

Add this to your crontab to create a weekly snapshot:

0 2 * * 0 /usr/bin/snap-slack create
0 3 * * 0 /usr/bin/snap-slack manage

Logging

Snap-slack logs all operations to /var/log/snap-slack.log. Check this file for troubleshooting if you encounter any issues.

Known Issues and Limitations

• The system doesn't support encrypted Btrfs volumes out of the box
• You must have enough disk space for snapshots
• The adopt operation requires a reboot to take effect
• Be careful when setting a very short retention period as it might delete snapshots you still need

Contributing

If you'd like to contribute to Snap-Slack, feel free to open an issue or submit a pull request on the project's repository.

License

This project is licensed under the MIT License.

Support

For help or support, feel free to open an issue on the repository.

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