Running OpenWRT in ESXi

The offical guide OpenWrt on x86 hardware (PC / VM / server) is a bit out date. Here are some notes.

The downloads link should be (https://downloads.openwrt.org/), which lists the latest version.
The Upcoming Stable Release should be fine, as many Chinese BBS have use v.22 now. And personally, I prefer nftables over old iptables so that I can skip learning some old fasion things. See OpenWrt 22.03 release notes.

An example download page link for /x86/64/ is 22.03.0-rc4,
Select generic-ext4-combined-efi.img.gz for a disk image uses a single read-write ext4 partition with no read-only squashfs root filesystem, which allows to enlarge the partition. However, features like Failsafe Mode or Factory Reset won’t be available as they need a read-only squashfs partition to function.

The image can boot in UEFI mode. As v.22, VMXNET3 is supported out-of-box, and NVMe SSD support is available since OpenWrt 21.02.

To convert to vmdk:

cp openwrt-22.03.0-rc4-x86-64-generic-ext4-combined-efi.img.gz openwrt2203.img.gz -a
gzip -d openwrt2203.img.gz
qemu-img convert -f raw -O vmdk openwrt2203.img openwrt2203.vmdk
scp openwrt2203.vmdk root@x.x.x.x:/vmfs/volumes/datastore1/iso/

Installation

Create a Linux VM for Other 5.x or later Linux (64-bit), named, eg. OpenWRT22. Remove its Hard disk 1 during creation.

On ESXi, terminal:

cd /vmfs/volumes/datastore1
vmkfstools -d thin -i iso/openwrt2203.vmdk OpenWRT22/OpenWRT22.vmdk

Add this OpenWRT22.vmdk as an Existing hard disk. Then, ESXi web page will highlight for a larger size, set it to 256 MB, or larger as your wish.

Resizing partitions

The guide use delete-and-create way for a larger one, and then update the GPT partition UUID in the GRUB configuration. It is better to copy the UUID and then set it back with gdisk.

Resizing filesystem

A forum post shows a better solution than later post on #11. However, the guide follow the #11 method, risking having two host to write to the same filesystem without knowing each other.

The solution also metions parted can resize a partition without having to delete it first.

Another way to the resize before convert raw disk image to vmdk. As it is easy to mount raw images under Linux.

qemu-img resize -f raw openwrt2203.vmdk 256M
LOOP="$(losetup -f)"
sudo losetup -P ${LOOP} openwrt2203.img
losetup -l
sudo fsck.ext4 -y ${LOOP}p2
sudo resize2fs ${LOOP}p2
sudo losetup -d $LOOP

The fsck.ext4 shows rootfs: clean, 1444/6656 files, 5072/26624 blocks, and does not change anything here.
Since no other one has mount it, the filesystem should be clean.

The resize2fs shows The filesystem is already 26624 (4k) blocks long. Nothing to do!.
However, it acrually write to the partition and change the image file hash value. For resized openwrt2203.img, SHA1 hash changes from 53eeb2cd54ba2f174429d99c298e4db1b4cf9ed1 to a new value.