I am not 100% sure this has to do with path lengths. Looking at the output of "ls" command you pasted, I think this has to do with the permissions of those directories. You will notice that the symlinked /pro/bin directory has "root" user permissions. I suspect you might be starting the server as a non-root user which is causing this access denial issue, resulting in the failure to launch that jar.
This doesn't appear to be a permissions issue. If I change ownership of the symbolic link to user wildfly and even execute the command as user wildfly, I still see the same output. For example:
[root@wildflytest wildfly]# chown -R wildfly:wildfly /opt/wildfly [root@wildflytest wildfly]# ls -ltr total 0 drwxr-xr-x. 11 wildfly wildfly 239 Feb 27 18:49 16.0.0 lrwxrwxrwx. 1 wildfly wildfly 6 Apr 25 11:33 pro -> 16.0.0 lrwxrwxrwx. 1 wildfly wildfly 28 Apr 25 11:33 configuration -> pro/standalone/configuration lrwxrwxrwx. 1 wildfly wildfly 18 Apr 25 11:33 log -> pro/standalone/log lrwxrwxrwx. 1 wildfly wildfly 7 May 7 08:05 bin -> pro/bin [root@wildflytest wildfly]# sudo -u wildfly bin/jboss-cli.sh --connect Error: Unable to access jarfile /opt/wildfly/jboss-modules.jar