Mantis attachments are imported as 0kb when imported into JIRA.

[신현재]

While migrating from Mantis to JIRA successfully, Attachments (Image file) looks like 0.0kb. And
In JIRA <data-directory> / data / attachments, attachments (Image files) are stacked and the file size is shown as 4 kb. In fact, it is difficult to distinguish whether the data in the <data-directory> / data / attachments path is normal data. Of course, I've done indexing. The attachments file may be corrupted, so I refer to the link below. But it is the same situation.

https://confluence.atlassian.com/jirakb/mantis-attachments-are-corrupted-upon-importing-to-jira-310378688.html

How should we deal with this phenomenon?

[Andy Heinzer]

The fact that all the attachments show 4kb in size is consistent with the idea that Jira was unable to actually retrieve the file from the mantis website.  As such, those files are likely some generic html / login page for the site.   

You should be able to perform this import again and select the 'specify credentials' checkbox.  When you select this checkbox you will then need to enter a the username and password for the mantis account that can login to that site and view all those attachments.  Note this is not necessarily the same credentials used below for accessing the Mantis database directly.

Another thing to test, Are you able to reach the mantis website from the Jira server itself?   Is this mantis site using SSL/HTTPS?

It would probably also help to look closely at the $JIRAHOME/log/atlassian-jira.log file from the time of the import itself.  If Jira is encountering any errors during the import this log should contain records of them and tell us more about the problems Jira might have encountered during the import.