I'm trying to follow the procedure in "Generating a VMkernel zdump manually from a dump file in ESXi host" (http://kb.vmware.com/kb/2081902) and get an error message:
Unable to copy the dump partition: WARNING: Start offset less than header size!
[root@TOPVCPESXi01:~] df -h
Filesystem Size Used Available Use% Mounted on
NFS 13.7G 92.0K 13.7G 0% /vmfs/volumes/NFS_vol01
VMFS-5 49.8G 973.0M 48.8G 2% /vmfs/volumes/TOPVCPESXi01-HDD1
VMFS-5 49.8G 1.2G 48.5G 2% /vmfs/volumes/TOPVCPESXi01-HDD2
VMFS-5 79.8G 975.0M 78.8G 1% /vmfs/volumes/iSCSI_vol01
VMFS-5 3.8G 663.0M 3.1G 17% /vmfs/volumes/TOPVCPESXi01_Flash1
VMFS-5 7.8G 871.0M 6.9G 11% /vmfs/volumes/TOPVCPESXi01_Flash2
vfat 249.7M 167.9M 81.8M 67% /vmfs/volumes/9f691e7f-5aef34de-7c69-e495051b6cfd
vfat 249.7M 167.9M 81.8M 67% /vmfs/volumes/bba0137d-45163325-50f6-9fce85fbd663
vfat 285.8M 202.6M 83.2M 71% /vmfs/volumes/5702fb79-60862c63-10b0-00505686d3de
[root@TOPVCPESXi01:~] esxcfg-dumppart --file --copy --devname active
DiagnosticPartition: Unable to copy the dump partition: WARNING: Start offset less than header size!
[root@TOPVCPESXi01:~]
[root@TOPVCPESXi01:~] esxcfg-dumppart --file --copy --devname active --zdumpname
/vmfs/volumes/TOPVCPESXi01-HDD1/coredump.dumpfile
DiagnosticPartition: Unable to copy the dump partition: WARNING: Start offset less than header size!
[root@TOPVCPESXi01:~]vmware -v
VMware ESXi 6.0.0 build-3620759
[root@TOPVCPESXi01:~]esxcli system coredump file get
Active: /vmfs/volumes/58f66671-5a5024fa-dfa0-000c297ef042/vmkdump/564D8C8A-F10A-42B4-43F9-4C7E7C7EF042.dumpfile
Configured: /vmfs/volumes/58f66671-5a5024fa-dfa0-000c297ef042/vmkdump/564D8C8A-F10A-42B4-43F9-4C7E7C7EF042.dumpfile
[root@TOPVCPESXi01:~]
If I deliberately cause a panic (vsish -e set /reliability/crashMe/Panic 1) ESXi is able to create dump to both local storage
I also faced same issue. My ESXi version is 6.7. Not able to collect vmkernel dump which i need to submit to DCPN case.