/etc/default/grub with your preferred editor (e.g. nano or vi).GRUB_DEFAULT to 2 (which means select 3rd entry by default) will let most of the virtual instances boot to installer automatically after timeout.GRUB_TIMEOUT timeout. You can just set GRUB_TIMEOUT=30 which will be fine.GRUB_HIDDEN_TIMEOUT_QUIET and GRUB_HIDDEN_TIMEOUT. Just delete them.Install dependencies:
sudo apt update && sudo apt -y install ca-certificates whois
Replace following <OPTIONS> with your options.
sudo sh -c "$(wget -qO- https://github.com/brentybh/debian-netboot/raw/master/netboot.sh)" -- <OPTIONS>
Remember to enter your current user's password for sudo (if need) and then enter the new user's password (if not specified by -p).
-c US Debian Installer Country-fqdn debian FQDN including hostname and domain. Priority: -fqdn option > rDNS > debian as default.-proto http Transport protocol for archive mirror only but not security repository (http, https, ftp)-host deb.debian.org Host for archive mirror only but not security repository-dir /debian Directory path relative to root of the mirror-suite stretch Suite (stable, testing, stretch, etc.)-u debian Username of admin account with sudo privilege-p secret Password of the account (if not specified, it will be asked interactively)-tz UTC Time zone-ntp pool.ntp.org NTP server-upgrade full-upgrade Whether to upgrade packages after debootstrap (none, safe-upgrade, full-upgrade)-s http://security.debian.org/debian-security Custom URL for security repository mirror-fs ext4 Filesystem for partition-ip 192.168.1.42 Configure network manually with an IP address (the following -cidr, -gw and -dns options only work when an IP address is specified)-cidr 255.255.255.0 Netmask for manual network configuration-gw 192.168.1.1 Gateway for manual network configuration-ns "8.8.8.8 8.8.4.4" DNS for manual network configuration-add "ca-certificates curl fail2ban openssl whois" Include individual additional packages to install-ssh secret Enable network console and specify password for SSH access during install process. You can login with installer user and check system logs.-dry-run Generate preseed.cfg and save to current dir but don't actually do anythingIf -c CN is used, Chinese Special options will be setup for good connectivity and experience against GFW.
https://chinanet.mirrors.ustc.edu.cn/debian.https://chinanet.mirrors.ustc.edu.cn/debian-security.Asia/Shanghai.cn.ntp.org.cn.156.154.70.5 156.154.71.5.sudo reboot with your SSH and the VM should reboot.GRUB_DEFAULT, it should be booted into installer automatically after timeout.New Install and enter it. Also, be quick, just do not miss the GRUB_TIMEOUT timeout you've set.