登入腾讯云后台，重装系统为Centos 7，使用初始密码ssh 登入系统
1.下载openbsd cd75.iso 镜像，dd 到虚拟本地磁盘/dev/vda

[root@VM-4-3-centos ~]# lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0     11:0    1 223.6M  0 rom
vda    253:0    0    30G  0 disk
└─vda1 253:1    0    30G  0 part /
[root@VM-4-3-centos ~]# wget https://cdn.openbsd.org/pub/OpenBSD/7.5/amd64/cd75.iso
--2024-05-20 20:59:11--  https://cdn.openbsd.org/pub/OpenBSD/7.5/amd64/cd75.iso
Resolving cdn.openbsd.org (cdn.openbsd.org)... 151.101.43.52, 2a04:4e42:a::820
Connecting to cdn.openbsd.org (cdn.openbsd.org)|151.101.43.52|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 11429888 (11M) [application/octet-stream]
Saving to: ‘cd75.iso’

100%[===================================================================================================================================================================================================>] 11,429,888  21.0MB/s   in 0.5s

2024-05-20 20:59:12 (21.0 MB/s) - ‘cd75.iso’ saved [11429888/11429888]
[root@VM-4-3-centos ~]# ll
total 11164
-rw-r--r-- 1 root root 11429888 Mar 21 05:54 cd75.iso
[root@VM-4-3-centos ~]# dd if=cd75.iso of=/dev/vda bs=512k
21+1 records in
21+1 records out
11429888 bytes (11 MB) copied, 0.00920571 s, 1.2 GB/s
[root@VM-4-3-centos ~]# reboot

重启进VNC 提示“not boot device” 失败
再次重装系统为Centos 7，使用初始密码ssh 登入系统

2.下载openbsd miniroot75.img 镜像，dd 到虚拟本地磁盘/dev/vda

[root@VM-4-3-centos ~]# lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0     11:0    1 223.6M  0 rom
vda    253:0    0    30G  0 disk
└─vda1 253:1    0    30G  0 part /
[root@VM-4-3-centos ~]# ll
total 0
[root@VM-4-3-centos ~]# wget https://cdn.openbsd.org/pub/OpenBSD/7.5/amd64/miniroot75.img
--2024-05-20 21:03:39--  https://cdn.openbsd.org/pub/OpenBSD/7.5/amd64/miniroot75.img
Resolving cdn.openbsd.org (cdn.openbsd.org)... 151.101.43.52, 2a04:4e42:a::820
Connecting to cdn.openbsd.org (cdn.openbsd.org)|151.101.43.52|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 5832704 (5.6M) [application/octet-stream]
Saving to: ‘miniroot75.img’

100%[===================================================================================================================================================================================================>] 5,832,704   13.8MB/s   in 0.4s

2024-05-20 21:03:39 (13.8 MB/s) - ‘miniroot75.img’ saved [5832704/5832704]

[root@VM-4-3-centos ~]# ls -lh
total 5.6M
-rw-r--r-- 1 root root 5.6M Mar 21 05:54 miniroot75.img
[root@VM-4-3-centos ~]# dd if=miniroot75.img of=/dev/vda bs=512k
11+1 records in
11+1 records out
5832704 bytes (5.8 MB) copied, 0.00625355 s, 933 MB/s
[root@VM-4-3-centos ~]# reboot

重启进VNC grub 花屏了 又失败
重装系统为Centos 7，使用初始密码ssh 登入系统

3.下载openbsd install75.img 镜像，dd 到虚拟本地磁盘/dev/vda

[root@VM-4-3-centos ~]# lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0     11:0    1 223.6M  0 rom
vda    253:0    0    30G  0 disk
└─vda1 253:1    0    30G  0 part /
[root@VM-4-3-centos ~]# wget https://cdn.openbsd.org/pub/OpenBSD/7.5/amd64/install75.img
--2024-05-20 21:14:45--  https://cdn.openbsd.org/pub/OpenBSD/7.5/amd64/install75.img
Resolving cdn.openbsd.org (cdn.openbsd.org)... 151.101.43.52, 2a04:4e42:a::820
Connecting to cdn.openbsd.org (cdn.openbsd.org)|151.101.43.52|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 696745984 (664M) [application/octet-stream]
Saving to: ‘install75.img’

100%[===================================================================================================================================================================================================>] 696,745,984 57.0MB/s   in 12s

2024-05-20 21:14:58 (54.0 MB/s) - ‘install75.img’ saved [696745984/696745984]

[root@VM-4-3-centos ~]# ls -lh
total 665M
-rw-r--r-- 1 root root 665M Mar 21 06:14 install75.img
[root@VM-4-3-centos ~]# fdisk -l

Disk /dev/vda: 32.2 GB, 32212254720 bytes, 62914560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0009ac89

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048    62914526    31456239+  83  Linux
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
1328+1 records in
1328+1 records out
696745984 bytes (697 MB) copied, 2.51045 s, 278 MB/s
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# dd if=install75.img of=/dev/vda bs=512k
Segmentation fault
[root@VM-4-3-centos ~]# reboot
Segmentation fault

直接dd sf了，又疯狂dd了好几次，重启命令也挂了，好家伙~直接腾讯云后台硬重启
重启时间有点长，重启完毕完了后进VNC看看，openbsd 文字安装向导出来了 NB!玄学

注：操作时候参考了以下文章：
https://marcocetica.com/posts/openbsd_digitalocean/
https://book.bsdcn.org/di-2-zhang-an-zhuang-freebsd/di-2.5-jie-teng-xun-yun-qing-liang-yun-ji-qi-ta-fu-wu-qi-dd-an-zhuang-freebsd
https://www.openbsd.org/faq/faq4.html#Download
https://cloudflare.cdn.openbsd.org/pub/OpenBSD/7.5/amd64/