Platform: All Platforms Versions:

Problem Description

How do I borrow license keys on a Floating Network License or a Class Kit License?


License borrowing means that you can use COMSOL (for a limited time) with a Floating Network License (FNL) or a Class Kit license (CKL) without a network connection to the license server. This can be convenient if you want to travel with a laptop for a limited time period and still want to be able to run COMSOL. The default maximum borrow period is one month.

Your COMSOL license needs to have Borrow enabled. If you are unsure about your license, please contact your software administrator or

From the File menu (Windows) or Options menu (Linux, Mac), select Licenses and Used Products from the main menu and click Borrow. Select the licenses you want to borrow from the list and specify the number of days you want to keep them. Click OK. Remember that other users cannot use the license keys that you have checked out. You can return the borrowed license keys early, before the borrowing period has expired, see below.

For license administrators: Control how users borrow licenses

It is possible to allow or block borrowing by certain users or certain computers. To do this, create an options file, LMCOMSOL.opt, which is saved in the same directory as the license.dat file on the license server computer. The options file allows administrators to control various usage parameters; the following instructions apply to borrowing:

  • INCLUDE_BORROW - Allow a user/group to borrow licenses. Other users/hosts are denied borrowing.
  • EXCLUDE_BORROW - Deny a user/group the ability to borrow licenses.
  • BORROW_LOWWATER - Set the number of licenses that cannot be borrowed.
  • MAX_BORROW_HOURS - Changes the maximum borrow period for the specified feature. The specified value must be lower than the value given as the maximum borrow period in the license file, which is 720 hours.

For examples on how to create the LMCOMSOL.opt options file, please see Knowledgebase entry 1058.

For a detailed description of the options file, please see the FlexNet Documentation: License Administration Guide which be found in the COMSOL Help Desk (choose Help->Documentation in the COMSOL Desktop).

Returning borrowed licenses manually

If features still seem to be borrowed even if the expiration date has passed, or if you like to return the borrowed licenses early, use the lmborrow command in the license/$arch directory in the COMSOL installation folder, where $arch is either win64 (64-bit Windows), glnxa64 (64-bit Linux), glnxarm64 (ARM Linux), maci64 (64-bit Mac), or macarm64 (ARM Mac).

Running the command ./lmborrow -status on will give you a list of all borrowed license features. (On Windows, the command would be lmutil lmborrow -status)

Each borrowed feature then has to be returned by the command ./lmborrow -return -c ../license.dat FEATURE, where FEATURE should be replaced with the name of a borrowed features, e.g., SERIAL, COMSOL, COMSOLGUI, COMSOLUSER etc.

On Windows the corresponding commands would be lmutil lmborrow -return -c ../license.dat FEATURE

To verify that the licenses have been returned, run ./lmborrow -status again. The output should be empty.


One reason that borrow will not work may be that the license file on the license server is not properly designed with the BORROW keyword. Please contact your system administrator if you suspect this.

Another reason may be that the license server is missing the required LSB libraries, please see Knowledgebase entry 1199 for more information.