Symptoms
Agent remote update on Linux with cPanel fails with the following error in trueimage-setup.log.
| 2021-08-20T10:20:46+1000:Create temp file /var/tmp/def_config error.
| 2021-08-20T10:20:46+1000:failed to get linux version: Create temp file /var/tmp/def_config error.
| 2021-08-20T10:20:46+1000:Failed to create temporary file '{0}': {1}
Cause
Issue is caused by cPanel's secure tmp feature that makes /var/tmp read-only.
Acronis installer uses /var/tmp as a storage for temporary files and cannot proceed without it.
Solution
Rebuild secure tmp from cPanel or turn off secure tmp.
See more details in this cPanel KB article.