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VMware ESXi

2 min readArticle

ESXi (Elastic Sky X integrated) is VMware's bare-metal hypervisor — it installs directly on the server hardware (no underlying OS) and runs virtual machines on top. It's the foundation of vSphere environments and is used everywhere in enterprise data centers.

Architecture

ESXi sits directly on hardware. VMs run on it. The management layer (vCenter) sits on top or separately. ESXi hosts can be clustered and managed centrally through vCenter Server.

shell 
Physical Hardware
      |
   ESXi Hypervisor
      |
  ┌───┴────┐
  VM1  VM2  VM3  (Guest OSes)

Accessing ESXi

bash 
# Web UI (Host Client) — new way
https://esxi-ip/ui

# Old way (deprecated) — vSphere Client (Flash)
https://esxi-ip/vsphere-client

# SSH access (must enable in host settings)
ssh root@esxi-ip

# Enable SSH via CLI if you have console access
vim-cmd hostsvc/enable_ssh
vim-cmd hostsvc/start_ssh

Useful ESXi Shell Commands

bash 
# List all VMs
vim-cmd vmsvc/getallvms

# Power on/off a VM (VMID from getallvms)
vim-cmd vmsvc/power.on 1
vim-cmd vmsvc/power.off 1
vim-cmd vmsvc/power.reset 1

# Get VM power state
vim-cmd vmsvc/power.getstate 1

# List datastores
esxcli storage filesystem list

# Network info
esxcli network ip interface list
esxcli network ip address list

# Hardware info
esxcli hardware cpu info
esxcli hardware memory stats get

# Running processes
esxcli system process list

# Firewall status
esxcli network firewall get
esxcli network firewall ruleset list

Datastore and VM Files

VMs are stored as files on datastores:

  • .vmx — VM configuration file
  • .vmdk — Virtual disk file(s)
  • .nvram — VM BIOS/EFI state
  • .log — VM logs
  • .vmss — Suspend state
bash 
# Browse datastore files
ls /vmfs/volumes/
ls /vmfs/volumes/datastore1/

# Copy a VM's vmdk (while VM is off)
cp /vmfs/volumes/datastore1/VM-Name/VM-Name.vmdk /vmfs/volumes/backup/

ESXi Security Considerations

  • Default root password — should be changed immediately after install
  • SSH is disabled by default — only enable when needed
  • Lock down the management interface to a VLAN
  • Enable ESXi shell and SSH timeout
  • Use vCenter for centralized auth with AD integration
  • ESXi CVEs have been critical — keep patched (2022+ saw several major vulns)

Patching ESXi

bash 
# Check current version
vmware -v

# Put host in maintenance mode first
esxcli system maintenanceMode set --enable true

# Apply offline patch bundle
esxcli software vib install -d /vmfs/volumes/datastore1/patch.zip

# Reboot
reboot

# Or use vSphere Lifecycle Manager (vLCM) from vCenter

Common Tasks

bash 
# Take snapshot of VM
vim-cmd vmsvc/snapshot.create 1 "pre-patch" "Before patching" 0 0

# List snapshots
vim-cmd vmsvc/snapshot.get 1

# Remove snapshot
vim-cmd vmsvc/snapshot.removeall 1

vSphere vs ESXi

  • ESXi — the hypervisor itself, runs on each physical host
  • vCenter — the management server for multiple ESXi hosts
  • vSphere — the product suite (ESXi + vCenter + other components)
  • ESXCLI — command-line management of ESXi
  • PowerCLI — PowerShell module for automating vSphere

See Also

  • future-of-tech-emerging-trends-2023 - VMware overview
  • vmware-fusion-guide - VMware Fusion (desktop)
  • vmware-workstation-guide - VMware Workstation (desktop)
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