User configuration 


An administrator can change user account properties, Protected Item, Storage Vault, Device, and Policy settings via the Comet Server web interface.

A user can change their own Protected Item and Storage Vault settings via the Comet Backup client application and the web interface.

The descriptions in this section apply to both situations.



Usernames must be at least six characters long, using only the characters a-z, A-Z, 0-9, underscore (_), period (.), at (@), and hyphen (-).

Usernames are case-sensitive.

Changes to username support 

Certain versions of Comet expanded the list of characters allowed in usernames. Usernames that are valid for newer versions of Comet may be invalid when used with older versions of Comet. This may impact certain scenarios including software downgrades and/or mixed-server-version replication.

If you have usernames that would be invalid under older versions of Comet, please take care to ensure that all your Comet infrastructure is upgraded past the point of conversion, to prevent any potential issues that may occur.

Future versions of Comet may allow characters from international alphabets in usernames (subject to Unicode normalization).


Passwords must be at least eight characters long.

The password must be on one line (no CR/LF bytes are permitted).

Any other characters are permitted, including spaces, special characters, symbols, and characters from international alphabets.


The user is able to set their own language.

As of Comet 18.12.0, the following languages are supported:

Language Code First introduced
English en_US
Spanish es_ES Comet Beta 1.0.0
Portuguese (Brazil) pt_BR Comet 17.3.2
Dutch nl_NL Comet 17.3.4
Italian it_IT Comet 17.9.0
German de_DE Comet 17.9.2
French fr_FR Comet 17.9.2
Croatian hr_HR Comet 17.12.6
Russian ru_RU Comet 18.5.0
Hebrew he_IL Comet 18.6.0
Portuguese (Europe) pt_PT Comet 18.12.0

Help translate Comet 

Our company is committed to making Comet available in multiple languages. Our staff mostly only speak English, so we contract translation companies to perform this work.

However, the best-quality translations come from our customers, who better understand the software and the backup industry. We would really appreciate any translation assistance you can offer.

If you want to correct a translation in Comet, or if you want to translate Comet into a new language, further information is available via CometBackup/translations at GitHub.


The Comet Backup client app resets the user's timezone automatically, to match the user's operating system timezone. An administrator can set the user's timezone to any valid IANA tzdata timezone. The default timezone for new accounts is always Etc/UTC.

The user's local timezone is used to calculate schedule times (e.g. a scheduled backup for "Friday 7 AM" means a different UTC instant depending on the customers' configured timezone).

Email addresses 

Comet Server has some built-in features to send email reports to customers. You can configure any number of email addresses for a user account.

Email addresses can be configured via Comet Server and via the Comet Backup client. An administrator can set an account policy to control whether users are allowed to modify their own email addresses.

Custom email reports 

The default backup report is an immediate email as soon as any backup job finishes.

Comet supports customising the email reports received by customers.

The following custom reports are available:

Report type Available in Schedule Description
Immediate job notification >= 18.9.3 Immediately when a job has completed The report contains the full job log
Summary table >= 18.9.4 Any schedule A table of jobs matching your custom search

Reports can be filtered to choose what jobs will be considered for the report. You can filter on a large number of criteria including but not limited to the job's type classification, status, start time, duration, Protected Item, and Storage Vault. For advanced queries, the search system supports boolean logic (AND/OR) and arbitrary-depth clause grouping.

You can send multiple reports for a single email address. This allows you to combine multiple report criteria.

For report templates allowing custom schedules, you can use any schedule supported by Comet's normal backup scheduler. Scheduled times are relative to each customer's configured local timezone.

  • Send jobs only on failure
    • Report 1
      • Type: "Immediate job notification"
      • Filter: "Status" "not equal" "Success"
  • Send reports for different Protected Items to different email addresses
    • Email address 1
      • Report 1
        • Type "Immediate job notification"
        • Filter: "Protected Item ID" "equal" "{one Protected Item}"
    • Email address 2
      • Report 1
        • Type "Immediate job notification"
        • Filter: "Protected Item ID" "equal" "{another Protected Item}"
  • Send only a daily summary of jobs
    • Report 1
      • Type: "Summary table"
      • Schedule: Daily at 07:00
      • Filter: "Time since job start" "less or equal" "24 hours"
  • Send only a weekly summary of jobs, but, also send immediate notifications on failure
    • Report 1
      • Type: "Immediate job notification"
      • Filter: "Status" "not equal" "Success"
    • Report 2
      • Type: "Summary table"
      • Schedule: Weekly on Friday at 12:00
      • Filter: "Time since job start" "less or equal" "7 days"


Comet Backup supports Quota restrictions based on different types of data measurements.

All Protected Items Quota 

You can set a limit on the maximum size of all Protected Items in the user's account. When a backup job is performed, the total size of Protected Items is checked against this quota, and the backup job will be aborted if it would exceed quota. If possible, the quota limits are checked before starting the backup, to avoid inconvenient interruptions and wasted bandwidth.

Device Limit 

You can set a limit on the number of devices that may be registered into the user's account. If a user tries to log in to this account using a new device, the registration will fail with an error message.

Storage Vault quota 

For more information about Storage Vault quota, please see the Storage Vault > Quota section below.

Suspending Accounts 

An administrator is able to suspend user accounts in Comet Server. An administrator can suspend a user account by clicking the 'Actions' button and choosing the 'Suspend' option. You can unsuspend a suspended account in the same way.

A suspended user cannot log in to the Comet Backup client and cannot backup nor restore any data. A user is not able to un-suspend themselves.

Protected Items 

Overview tab 

In the "Description" field, enter a brief name describing what data is being backed up. Select which type of data is to be protected.

Items tab 

For more information about the settings for each Protected Item type, please see the Protected Item documentation.


Comet can run backup jobs automatically on a schedule. It is strongly recommended to automate your backups on a regular schedule.

Click the plus button to add a new schedule.

General Schedule options 

When a schedule is due to run, the backup job will run automatically to the selected Storage Vault.

You can also configure advanced backup runtime options:

  • Skip if already running. If this option is enabled, and another backup job is known by the Comet Server to exist for the same Protected Item and Storage Vault in "Running" status, then this backup job will be skipped. Skipping a backup job creates a log entry for the job in "Skipped" status.
  • Cancel if still running after. You can set a time limit for the backup job. If the backup job exceeds this time limit, the backup job would be cancelled.
  • Limit Storage Vault Speed. This option allows you to limit the total speed that Comet reads and writes to the Storage Vault. The speed limit applies to the total combined read/write bandwidth.
  • Limit backup to use only 1 disk thread. When reading multiple files from the local disk for backup, Comet Backup uses multithreading to improve performance. On some machines, this can impact PC performance. If you are experiencing low system performance while the backup job is running, you can try enabling this option to see if it resolves the issue.
  • Prefer temporary files instead of RAM (slower). This option reduces backup job performance.
  • Allow backup of zero files to succeed. If a backup job completes successfully but did not include any files in the backup, Comet will by default mark the job as "Error" status. This is a useful feature to help detect against accidental path changes or incorrect file selections. However in some cases you may expect a backup job to succeed with no files included. In that case, you can enable this option.

Schedule times 

You can configure the times when this schedule will be executed. You can add multiple times to the same schedule.

The available time-based schedule frequencies are:

  • Hourly. The schedule would run every hour. You can choose the minutes past the hour.
  • Daily. The schedule would run every day. You can choose the time of day (hours/minutes). The hours are specified in 24-hour time, from 0 to 23.
  • Weekly. The schedule would run every week. You can choose the day of the week, and the time of day (hours/minutes). You can choose multiple days of the week.
  • Monthly. The schedule would run every month.
  • Once only. The schedule would run only when the specified date and time is reached.
  • Periodic. The schedule would run regularly at the set frequency. You can use the "Offset" option to help stagger multiple devices that might otherwise all start running simultaneously.

If the device is online, Comet Backup will try to run the backup job. If the device is not online, or the backup job could not be started, the Comet Server will inject a "Missed" job into the customer's backup job log. Administrators can use these "Missed" backup job notifications when monitoring the job history for their customers, to ensure that backup jobs run on schedule.

Event-based schedule frequencies are also available.

The available event-based schedule frequencies are:

  • Also run when PC starts. The schedule would be initiated immediately after the PC boots.
  • Also run when PC starts, if the last job was Missed. The schedule would be initiated immediately after the PC boots if the last backup job for this Protected Item and Storage Vault pair was in Missed status. This allows you to "catch up" missed backups for PCs that are only online at irregular intervals (e.g. laptops).

The time that the "PC starts" is defined as follows: the time that the Comet Backup background service started, if the system uptime is less than 10 minutes. (This definition is subject to change.)

Commands (Schedule) 

You can configure Commands that run before/after this Schedule runs.

The Commands feature on a Schedule works the same way as for Commands on a Protected Item or on a Storage Vault. For more information about the Commands feature, please see details under the Overview and Concepts section.

Commands (Protected Item) 

You can configure Commands that run before/after this Protected Item is backed up.

The Commands feature on a Protected Item works the same way as for Commands on a Storage Vault or on a Schedule. For more information about the Commands feature, please see details under the Overview and Concepts section.

Retention (Protected Item) 

On the Retention tab, you can configure a retention policy to apply when backing up this Protected Item to a specific Storage Vault. If no policy is configured for a specific Storage Vault, the default retention policy for the Storage Vault will apply.

Retention (Storage Vault) 

"Retention" is the concept of classifying backed-up data, to determine what data should be kept, and what data can be safely removed in order to free up disk space. For instance, you may choose to keep the last 30 days' of backed-up data, or all data from the last 100 backup jobs; but any data older than this is unlikely to be useful and can be safely removed.

Retention Pass 

A "retention pass" is the act of cleaning up data from the Storage Vault that exceeds the configured retention policy.

During a retention pass, Comet Backup looks at each backed-up job within the Storage Vault and determines whether it meets the retention policy. If the retention policy states that the backed-up job can be safely removed, the backed-up job is removed from the Storage Vault. Once all backed-up jobs are checked against the retention policy, any data chunks that are no longer referenced by a backed-up job can then be pruned to save disk space.

Automatic retention passes 

A retention pass may run automatically after each backup job.

Because the retention pass is a destructive action, it temporarily requires the Storage Vault to be completely idle, to take exclusive control over the Storage Vault. Comet Backup has to determine a possible idle time. Without loss of generality, any possible idle-time always occurs at the end of some backup job. By checking at the end of a backup job as to whether the Storage Vault is idle, Comet is guaranteed to find the idle time-window as long as such a time-window exists.

An automatic retention pass is not necessarily critical, and so if a backup job comes to an end without the Storage Vault being idle, the retention pass is not immediately "overdue".

The "overdue" rules for automatic retention passes are based on the time since the previous successful retention pass, and, the number of jobs exceeding the configured retention policy. The exact rules are subject to change in future versions of Comet. As of Comet 19.12.4, the rules are as follows:

Last retention pass 0-2 jobs exceeding policy 3-9 jobs 10-49 jobs 50+ jobs
less than 24 hours ago None Attempt Attempt Require
between 24 hours ago and 14 days ago None Attempt Require Require
between 14 days ago and 21 days ago Attempt Attempt Require Require
over 21 days ago, or never ran Require Require Require Require

In the above table,

  • "None" means that no automatic retention pass will be attempted at the end of the backup job
  • "Attempt" means that Comet will attempt a retention pass, but not throw an error if the Storage Vault is still busy
  • "Require" means that Comet will attempt a retention pass, and will throw an error if the Storage Vault is still busy

Manual retention passes 

You can run a retention pass for a Storage Vault on demand, by right-clicking the Storage Vault within the Comet Backup application, or an administrator can remotely initiate this by using the live-connection action from the Comet Server web interface.

In this case because the action was explicitly taken, an error will be raised if the job fails to be performed for any reason.


Comet allows you to configure retention for a Storage Vault, as well as for a Protected Item / Storage Vault pair.

The retention rule for the pair will be used in preference to the retention rule for the Storage Vault. The retention rule for the Storage Vault is therefore only applied when

  • there is no overridden retention rule for the Protected Item / Storage Vault pair; or
  • the Protected Item is unknown, deleted, or belongs to a different Comet user account

Retention policies 

There are two categories of retention policy:

  • A policy that keeps all data forever, and
  • A policy that keeps data as long as it falls within any of a set of configurable ranges. You can combine multiple ranges to create a more complex policy.

Retention ranges 

A retention range is a time period or job count during which a backup job should be kept.

The following ranges are available:

Range Parameters Description
Last [...] backups Specify a number of backups to keep. If the backup job was within the last X backups, then the backup job will be kept
All backups in the last [...] Specify a number of days, weeks, and/or months. If the backup job occurred recently within the specified range, then the backup job will be kept
All backups newer than a specific date Specify a specific date. If the backup job occurred after that specific date, then the backup job will be kept
One backup each day, for the last [...] days Specify a number of days. Comet will keep the single first backup job from each of that most recent days
One backup each week, for the last [...] weeks Specify a number of weeks, and a day of the week Comet will keep the single first backup job that occurred on that day of the wek, for each of that number of most recent weeks
One backup each month, for the last [...] months Specify a number of months, and a calendar date Comet will keep the single first backup job that occurred on that calendar date, for each of that number of most recent months

Future versions of Comet may make additional Retention Range options available.

Storage Vaults 

General tab 

On this tab, you can give a name to the Storage Vault. You can use any name; if you have multiple Storage Vaults within an account, we would recommend using a name that identifies the content and/or purpose of the Storage Vault.

On this tab, you can also configure a retention policy for the Storage Vault.

Quota (Storage Vault) 

On this tab, an administrator using Comet Server can configure a quota limit, restricting the total amount of data stored within this Storage Vault.

You can set this property on a per-Storage Vault basis. For example, you could use this feature to limit the amount of data stored on an expensive network storage account, but still allow any amount of data to be stored on a local hard drive.

When a backup job is performed, the total size of the Storage Vault is measured and checked against this quota limit. As the job proceeds, the amount of uploaded data is compared against the remaining available size, and the backup job will be aborted once reaching this limit.

After a quota has been exceeded 

A backup job that is abandoned for reaching its Storage Vault quota does not remove the chunks that were uploaded to the Storage Vault. Future backup jobs will almost certainly fail immediately. In this situation, you have the choice between

  1. Raising the Storage Vault quota and retrying the backup. This will cause any existing chunks in the vault to be re-used, accelerating the backup quickly up to the point where it was interrupted; or
  2. Using the "Apply retention rules now" feature to clear unused chunks from the Storage Vault. This will reduce the data size within the Storage Vault and allow future backups to proceed.

Neither action is taken automatically - you should choose one action to take depending on the situation.

Storage tab 

On this tab, you can configure the data storage location for this Storage Vault. A number of types are available, including local disk storage, network accounts, and cloud storage providers. For more information about data storage locations, please see the Storage Configuration documentation.


The Commands feature on a Protected Item works the same way as for Commands on a Storage Vault or on a Schedule. For more information about the Commands feature, please see details under the Overview and Concepts section.


Comet automatically enables encryption for all Storage Vaults. This is not customizable; this tab solely serves to indicate that fact to unaware users.

Storage Vault encryption is initialized upon first-use. You can use this tab to tell whether a Storage Vault has been initialized with an encryption key, and when the initialization was performed (according to records in the user account profile).


You can log in to the same user account from multiple devices.

Each device in an account has their own private Protected Items, but shares the Storage Vaults. Because Storage Vaults are the unit of deduplication, all backups from all devices in the account can be deduplicated against each other. This also means that devices can restore each others' data.

An administrator can revoke devices from your account.

A device has a "friendly name" that is set by the device when it is first registered. The "friendly name" defaults to the hostname of the PC. An administrator can rename devices in an account.

Because additional devices may incur a cost, an administrator can also limit the total number of devices in an account.

If a device is live-connected to the Comet Server, an administrator can request that the device performs certain actions.


An administrator can apply additional restrictions to user accounts, using the Policies feature in the Comet Server web interface. For more information about the Policies feature, please see details under the Comet Server Usage - Policies section.