Configuring Sync

Many parameters of Sync can be configured by using the asconfigurator tool from the command line or by editing the file_system and default sections of aspera.conf. To configure Sync using asconfigurator, use this general syntax:

# /opt/aspera/bin/asconfigurator -x "set_node_data;option,value"

Possible options and values are described below.

To manually edit aspera.conf, open it in a text editor with administrative privileges.


See an example of the asperawatchd configuration in aspera.conf below.

You must validate aspera.conf after manually editing it to confirm that your configuration is correct. Run the following command:

# /opt/aspera/bin/asuserdata -v

To view the current settings, run the following command:

# /opt/aspera/bin/asuserdata -a

Sync Configuration Options

The table below provides a reference of many of the configuration options for use with Sync.

asconfigurator option
aspera.conf setting

Description and Value Options


Specify the directory creation mode (permissions). If specified, create directories with these permissions irrespective of <directory_create_grant_mask> and permissions of the directory on the source computer. This option is applied only when the server is a Unix-based receiver.

Value is a positive integer (octal). (Default: undefined)


Specify the mode for newly created directories if directory_create_mode is not specified. If specified, directory modes are set to their original modes plus the grant mask values. This option is applied only when the server is a Unix-based receiver and when directory_create_mode is not specified.

Value is a positive integer (octal). (Default: 755)


Specify if the ACL access data (acls) or extended attributes (xattrs) from Windows or Mac OS X files are preserved. Three modes are supported. (Default: none)

native: acls or xattrs are preserved by using the native capabilities of the file system. If the destination does not support acls or xattrs, async generates an error and exits.

metafile: acls or xattrs are preserved in a separate file. The file is in the same location and has same name, but has the added extension .aspera-meta. The .aspera-meta files are platform-independent, and files can be reverted to native form if they are synced with a compatible system.

none: No acls or xattrs data is preserved. This mode is supported on all file systems.

ACL preservation is only meaningful if both hosts are in the same domain. If a SID (security ID) in a source file does not exist at a destination, the sync proceeds but no ACL data is saved and the log records that the ACL was not applied.

The aspera.conf settings for acls or xattrs can be overwritten by using the --preserve-acls or --preserve-xattrs options, respectively, in a command-line async session.


Value has the syntax sqlite:lock_style:storage_style. (Default: undefined)

lock_style: Specify how async interfaces with the operating system. Values depend on operating system.

Unix-based systems have the following options:
  • empty or unix: The default method that is used by most applications.
  • unix-flock: For file systems that do not support POSIX locking style.
  • unix-dotfile: For file systems that do not support POSIX nor flock-locking styles.
  • unix-none: No database-locking mechanism is used. Allowing a single database to be accessed by multiple clients is not safe with this option.

storage_style: Specify where Sync stores a local database that traces each directory and file. Three values can be used:

  • undefined or disk: The default option. The database reads and writes to disk. This provides maximum reliability and no limitations on the number of files that can be synced.
  • lms: The database is loaded from disk to memory at startup, changes during the session are saved to memory, and the database is saved to disk on exit. This option increases speed but all changes are lost if async stops abruptly, and the number of synced files is limited by memory availability.
  • memory: The database is stored completely in memory. This method provides maximum speed but is not reliable because the database is not backed up to disk.


The number of seconds async waits for a connection to be established before it terminates.

Value is a positive integer. (Default: 20)


The number of seconds async waits for a non-responsive session to resume before it terminates.

Value is a positive integer. (Default: 20)


Specify an alternative location for the async server's log files. If unspecified, log files are saved in the default location or the location that is specified by the client with the -R option. For information on the default log file location, see Logging.


Set the amount of detail in the async server activity log. Valid values are disable, log (default), dbg1, or dbg2.

Example Sync Configuration in aspera.conf

   <directory_create_mode> </directory_create_mode> 
   <async_db_spec>  </async_db_spec>