ConQuest fails to start on some versions of Linux with an import error about libk5crypto.so.3

Modified on Wed, 17 Dec, 2025 at 1:54 PM

On some versions of Linux ConQuest or cqbatch may fail to start with an error like this.

Traceback (most recent call last):
  File "cqbatch.py", line 4, in <module>
  File "/opt/ccdc/third-party/conquest_python/conquest_python-2.7.18-9-linux/lib/python2.7/site-packages/PyInstaller/loader/pyimod03_importers.py", line 395, in load_module
  File "system.py", line 9, in <module>
  File "/opt/ccdc/third-party/conquest_python/conquest_python-2.7.18-9-linux/lib/python2.7/site-packages/PyInstaller/loader/pyimod03_importers.py", line 395, in load_module
  File "commoncode/dblist.py", line 9, in <module>
  File "/opt/ccdc/third-party/conquest_python/conquest_python-2.7.18-9-linux/lib/python2.7/site-packages/PyInstaller/loader/pyimod03_importers.py", line 395, in load_module
  File "database/entry_reader.py", line 24, in <module>
  File "/opt/ccdc/third-party/conquest_python/conquest_python-2.7.18-9-linux/lib/python2.7/site-packages/PyInstaller/loader/pyimod03_importers.py", line 395, in load_module
  File "database/conquest_aser_adapter.py", line 10, in <module>
  File "/opt/ccdc/third-party/conquest_python/conquest_python-2.7.18-9-linux/lib/python2.7/site-packages/PyInstaller/loader/pyimod03_importers.py", line 684, in load_module
ImportError: /mnt/CCDC/ccdc-software/conquest/lib/libk5crypto.so.3: undefined symbol: EVP_KDF_ctrl, version OPENSSL_1_1_1b
[2415] Failed to execute script cqbatch

The recommended solution is to update your installation to the latest release (2025.3.1 at the date of writing). If the error persists or ConQuest starts up but without the 3D visualiser, ensure that your Linux system is up to date and all the prerequisites listed in the Release And Installation Notes are installed.

On Ubuntu 22/24 and RHEL 9/10 and clones you may also have to remove the files libstdc++.so.6 and libgcc_s.so.1 in CCDC/ccdc-software/conquest/lib.
On RHEL 8 and clones you may also have to remove the files libcrypto.so.1.1 and libssl.so.1.1 in the same directory.