Exploring Backup Structure

This tutorial helps Virtualmin users understand what’s inside a Virtualmin backup file, explaining how backup files are named, what each file represents, and how file structures differ depending on your chosen backup format.

Virtualmin backups store your server data in a single downloadable file, which, when extracted, reveals multiple smaller files. Knowing how these files are organized makes troubleshooting, manual restores, or accessing specific data easier.

Backup file formats

Virtualmin creates backup archives using different compression formats based on your selection:

• TAR with GZ: Creates .tar.gz files using GNU Tar with gzip compression
• TAR with BZIP2: Creates .tar.bz2 files with better compression but slower processing
• TAR: Creates uncompressed .tar archives with no compression
• ZIP: Creates .zip files with compression, compatible with most systems
• TAR with ZSTD: Creates .tar.zst files with modern, efficient compression

Understanding the file structure

When you extract a Virtualmin backup, you’ll see lots of files with names like domain.tld_* or virtualmin_*. These files are divided into two main groups: those related to your domain and those for the global Virtualmin system configuration. Let’s break it down.

Domain-specific files

Each virtual server (domain) has its own set of files, all prefixed with the domain name. For example, if your domain is domain.tld, you’ll see files ending with an underscore followed by the Virtualmin feature name, for example:

domain.tld_dir

Contains the entire home directory of the domain, including all website files, user data, and mail directories. This is typically the largest file in the backup.

domain.tld_dns

Stores DNS configuration for the domain, including zone file settings and nameserver records.

domain.tld_logrotate

Log rotation configuration that determines how your server logs (like webserver access and error logs) are rotated and stored.

domain.tld_mail_*

Multiple files handling email configuration.

domain.tld_mysql

Database server configuration.

domain.tld_mysql_[dbname]

Individual database dumps. Each database gets its own file containing all tables and data.

domain.tld_spam_*

Spam filtering configurations including SpamAssassin rules and user preferences.

domain.tld_ssl_*

SSL certificate files.

domain.tld_virtualmin

Contains domain-specific configuration, including domain user and group, assigned IP addresses, enabled features, and other domain-related settings.

domain.tld_virtualmin-[plugin]

Configuration or actual backup files for Virtualmin plugins like AWStats or WP Workbench.

domain.tld_web

Apache webserver configuration for the domain.

domain.tld_web_[ae]log

Access and error log files.

domain.tld_webmin

Webmin access permission settings for the domain owner for different Webmin modules.

Global configuration files

Virtualmin system-wide settings are stored in files beginning with virtualmin_, for example:

virtualmin_config

Main Virtualmin module config containing global settings and feature defaults.

virtualmin_templates

Server templates that define default settings for new domains.

virtualmin_templates_plans

Account plans with resource limits and feature sets.

virtualmin_mailserver_*

Global mail server configuration for Postfix, OpenDKIM, and other mail-related settings.

virtualmin_resellers

Reseller account information and permissions.

virtualmin_scheds

Scheduled backup configurations.

virtualmin_scripts

Script installer data and configurations.

virtualmin_email

Email templates for automated messages.

Backup modes and file organization

Virtualmin offers two backup modes that organize your backup files a little differently within the main archive.

• Single archive file mode

  This is the standard backup mode. All components are stored as separate files in the main archive, as described above, for example:

  backup-file.tar.gz
  ├── domain.tld_dir
  ├── domain.tld_dns
  ├── domain.tld_mysql
  ├── domain.tld_web
  ├── virtualmin_config
  └── [other component files]
  

• One file per server mode

  This mode reorganizes the backup for direct access to website files. The home directory contents are placed directly at the archive root. All other components are moved to a .backup directory. For example:

  backup-file.tar.gz
  ├── .backup/
  │   ├── domain.tld_dir (empty)
  │   ├── domain.tld_dns
  │   ├── domain.tld_mysql
  │   ├── domain.tld_web
  │   ├── virtualmin_config
  │   └── [other component files]
  ├── Maildir/
  ├── bin/
  ├── cgi-bin/
  ├── domains/
  ├── etc/
  ├── homes/
  ├── logs/
  ├── public_html/
  ├── tmp/
  ├── .bash_history
  ├── .bash_logout
  ├── .bash_profile
  └── .bashrc
  

The internal file names and content stay the same in both modes; only the organization within the archive changes.

Compression format of nested archives

The format of nested archives within the backup matches your chosen compression method, but regardless of whether “tar” or “zip” is used, these nested archives remain uncompressed, as they simply group files together without reducing their size. The internal structure stays consistent; only the archive handling varies based on your selection.

Conclusion

Virtualmin backup files have a clear structure that makes managing your data easy. Files starting with your domain name contain specific data and settings, like website files, DNS records, or databases, while other files contain settings that apply globally across the entire Virtualmin system.

No matter which compression method you choose, the internal organization stays consistent.