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# Operations Explained

AutoArchive can execute several commands. Besides the backup creation—its main function—it can show list of configured and orphaned archives displaying various information about them, or perform a cleaning action that wipes the orphaned archive data. The operation is chosen by specifying the corresponding command as a program’s argument. For list of all commands see the Usage section.

## Configuring the Archive

One of the actions that is actually not handled by the AutoArchive is the configuration of the archive. In order to be able to create a backup AutoArchive has to be provided by an archive specification file. It needs to be created manually and placed to archive specifications directory or path to it passed as the program’s argument. Archive specification file is a plain text file with simple structure which is described in the Configuration File section. Sample files are distributed with the program and an example is provided also in the Configuring the Archive Example section.

## Backup Creation

Main AutoArchive’s function is the backup creation. It is the default operation so no command needs to be specified in order to create one. Name or path to an archive specification file is required unless `--all` option is given. By default non-incremental tar.gz backup is created in the current directory. This can be changed with options on the command line, configuration files or the archive specification file itself. A simple example of the backup creation is shown in the Backup Creation Example section. See also Usage, Configuration File and Archive Specification File sections for all possible configuration options.

### Incremental Backup Creation

Passing `-i` option on the commandline or specifying corresponding configuration option in a configuration file causes creation of incremental backups. In this case a single full backup is created upon first execution. Subsequent executions will create diff backups with increasing backup level. To restore a backup the full backup plus all increments (or all increment up to the desired restoration point) are required. Options for manual or automatic restarting to a particular lower level are available. When restarting is applied option `--remove-obsolete-backups` can be specified to remove backups that becomes obsolete due to the restart.

### Keeping old backups

In order to reduce risk of losing a valuable older backup AutoArchive can keep backups which are going to be removed or overwritten during a new backup creation. This feature makes possible to have desired number of older backups always available with or without using the incremental archiving. To enable it use `-k` option and to specify desired number of kept backups use the `--number-of-old-backups=NUM` option. The option `--remove-obsolete-backups` can be used to automatically remove kept backups which may become obsolete due to lowering the `--number-of-old-backups=NUM` value.

Each kept backup (or series of kept backup increments in case of incremental archiving) has its own keeping ID. The most recent kept backup gets keeping ID ‘aa’, second most recent gets ‘ab’ and so on up to maximal value ‘zz’ (which is by default further limited by `--number-of-old-backups=NUM`). When a new backup is going to be kept back all existing kept backup are shifted so that they get higher keeping ID. Backups with keeping ID ‘aa’ will get ‘ab’, those with ‘ab’ gets ‘ac’ and so on. When number of kept backups would exceed value of the `--number-of-old-backups=NUM` option the last kept backup (with highest keeping ID) is removed.

Refer to Backup Keeping section for an example.

## Listing Archives

In order to list all archives and show information about them the `--list` command is provided. By default it shows all archives that are known to AutoArchive and orphaned archives. Note that “archive” here means the “archive configuration”, which is represented by the archive specification file, not the result of the backup creation (the *.tar.gz file). If one or more names or paths to archive specification files are passed as arguments it lists only those.

The output has two forms: normal and verbose.

### Normal output

The structure of the normal `--list` output is following:

    <Name> <Root> <Destination directory> <Current backup level/next/max.>

An archive per line is listed.

### Verbose output

If `--verbose` option is specified alongside with `--list` the verbose form is printed. It shows following information:

    Name:
    Root:
    Archiver type:
    Destination directory:
    Current backup level/next/max.:
    Target backup level for non-full restart:
    Upcoming restart reason:
    Restart count/max.:
    Days since last restart/max.:
    Days since last full restart/max.:

The meaning of the particular fields is:

Name
  Archive name as determined from archive specification file name or the `name` option.
Root
  Archive’s root path as configured with `path` option.
Archiver type
  Type of the archiver as configured with the `archiver` option.
Destination directory
  Directory where the backup will be created as configured with the `dest-dir` option.
Current backup level/next/max.
  Corresponds to “Current backup level/Next backup level/Maximal backup level”. Current backup level is the backup level that was created in last backup creation. Next backup level is the backup level that will be created in next backup creation (if restarting is enabled it will not be always the next level in a row). Maximal backup level is the value configured with the `restart-after-level` option.
Target backup level for non-full restart
  Backup level to which will be restarted to in case of non-full backup level restart (for example if `restart-after-level` value is reached. It is typically 1 but can be higher due to `max-restart-level-size` option.
Upcoming restart reason
  Show the reason of following backup level restart.
Restart count/max.
  Number of non-full backup level restarts and maximal number of restarts as configured with the `full-restart-after-count` option.
Days since last restart/max.
  Number of days since last non-full backup level restart occurred and maximal number of days without a restart as configured with the `restart-after-age` option.
Days since last full restart/max.
  Number of days since last full backup level restart occurred and maximal number of days without a full restart as configured with the `full-restart-after-age` option.

### Value format

If the value is enclosed in square brackets ([]) it means that it is not relevant to the current archive configuration. For example if an archive was previously configured as incremental and some incremental backups were already created, and its configuration was changed to non-incremental later, then the actual backup levels are shown but they are enclosed in square brackets. In case of orphaned archives the name is enclosed in square brackets.

If the value is not applicable or not available a dash (-) is printed instead.

Sometimes a question mark (?) is printed instead of the value which means that the value could not be determined while it is expected to be available. This happens mostly for orphaned archives where only a limited number of information is available.

## Cleaning Orphaned Information

Orphaned archives shown in the `--list` output with their names enclosed in square brackets does not have a corresponding archive specification file. It is just leftover information saved in a previous backup creation operation (it is not the backup itself). This information can be removed with the `--purge` command. It may be provided with the orphaned archive name in order to remove information about that particular archive or with the `--all` option in order to remove information about all orphaned archives.

Note that the `--purge` command does not remove created backups.

## Restoration of the Backup

AutoArchive does not handle backup restoration by itself. Backups can be restored by using standard GNU tar archiver or any other tar-compatible archiver. Please see the GNU tar documentation for more information or the Backup Restoration Example section for examples on restoring backups.

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