Nov 27 00:50:02 syslogd started: BusyBox v1.1.3
Nov 27 00:50:02 kernel: klogd started: BusyBox v1.1.3 (Debian 1:1.1.3-4)
Nov 27 00:50:02 kernel: 0
Nov 27 00:50:02 kernel: ACPI: PM-Timer IO Port: 0x1008
Nov 27 00:50:02 kernel: ACPI: Local APIC address 0xfee00000
Nov 27 00:50:02 kernel: ACPI: 2 duplicate APIC table ignored.
From here we can see that Debian install CD start by the support of BusyBox, which is a small implementaion of the Unix envrioment.
Then, everything will be charged by the Kernel, it will do everyting as the PC boots, such as detect the hardware, do some initliazation, etc.
When installing this system again, i found that the boot of install CD, live CD and usb boot are the work at the same way with hard disk installed system booting, the steps should be:
Start machine from some media such as CD/DVD/USB Flash Memory/IDE HDD,
load the system loader, such as Grub, etc. The first menu of Debian installation CD is a system loader too, it's very familar with Grub, in most conditions, the loader will interact with the user, it can load the Kernel and start the system as the perameter requested.
Then, The Loader will load Kernel, and then the Busybox, and it's here the /var/log/installer/syslog starting, the following steps we can find records in this file.