剛做了一些探索，「紀錄在這裡」。

用來補充我上一個「回覆」說的

samwhelp 寫到：

自由車自由人 寫到：
首先，不要編輯 /boot/grub/grub.cfg 檔案，這是 GRUB 2 才有的
基本上它就像是一個暫存檔，或說沙盒，過一陣子就會被自動重設

我的觀察是，當更新kernel套件時，感覺就會觸發執行「update-grub」這個動作。
不過這只是我觀察到的，我猜這應該跟「DpkgTriggers」的機制有關(後記: 應該跟「MaintainerScripts」有關)，
還沒額外的時間去找到相關的程式碼，和掌握整個機制的全貌。


我目前有看到一個疑似的檔案「/etc/kernel/postinst.d/zz-update-grub」，不過我還沒確定，只是先提出來。

我說的觀察到的，是從類似下面的訊息觀察來的，產生這個訊息的步驟紀錄在「這篇」，進一步的探索，則是紀錄在「這篇」。

Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
linux-headers-4.4.0-28 linux-headers-4.4.0-28-generic linux-headers-generic linux-image-4.4.0-28-generic linux-image-extra-4.4.0-28-generic
linux-image-generic
Suggested packages:
fdutils linux-doc-4.4.0 | linux-source-4.4.0 linux-tools
The following NEW packages will be installed:
linux-headers-4.4.0-28 linux-headers-4.4.0-28-generic linux-image-4.4.0-28-generic linux-image-extra-4.4.0-28-generic
The following packages will be upgraded:
linux-generic linux-headers-generic linux-image-generic
3 upgraded, 4 newly installed, 0 to remove and 203 not upgraded.
Need to get 68.3 MB of archives.
After this operation, 295 MB of additional disk space will be used.
Do you want to continue? [Y/n]
Get:1 http://tw.archive.ubuntu.com/ubuntu xenial-updates/main amd64 linux-image-4.4.0-28-generic amd64 4.4.0-28.47 [18.7 MB]
Get:2 http://tw.archive.ubuntu.com/ubuntu xenial-updates/main amd64 linux-image-extra-4.4.0-28-generic amd64 4.4.0-28.47 [38.8 MB]
Get:3 http://tw.archive.ubuntu.com/ubuntu xenial-updates/main amd64 linux-generic amd64 4.4.0.28.30 [1790 B]
Get:4 http://tw.archive.ubuntu.com/ubuntu xenial-updates/main amd64 linux-image-generic amd64 4.4.0.28.30 [2332 B]
Get:5 http://tw.archive.ubuntu.com/ubuntu xenial-updates/main amd64 linux-headers-4.4.0-28 all 4.4.0-28.47 [9944 kB]
Get:6 http://tw.archive.ubuntu.com/ubuntu xenial-updates/main amd64 linux-headers-4.4.0-28-generic amd64 4.4.0-28.47 [790 kB]
Get:7 http://tw.archive.ubuntu.com/ubuntu xenial-updates/main amd64 linux-headers-generic amd64 4.4.0.28.30 [2306 B]
Fetched 68.3 MB in 29min 13s (39.0 kB/s)
Selecting previously unselected package linux-image-4.4.0-28-generic.
(Reading database ... 154656 files and directories currently installed.)
Preparing to unpack .../linux-image-4.4.0-28-generic_4.4.0-28.47_amd64.deb ...
Done.
Unpacking linux-image-4.4.0-28-generic (4.4.0-28.47) ...
Selecting previously unselected package linux-image-extra-4.4.0-28-generic.
Preparing to unpack .../linux-image-extra-4.4.0-28-generic_4.4.0-28.47_amd64.deb ...
Unpacking linux-image-extra-4.4.0-28-generic (4.4.0-28.47) ...
Preparing to unpack .../linux-generic_4.4.0.28.30_amd64.deb ...
Unpacking linux-generic (4.4.0.28.30) over (4.4.0.21.22) ...
Preparing to unpack .../linux-image-generic_4.4.0.28.30_amd64.deb ...
Unpacking linux-image-generic (4.4.0.28.30) over (4.4.0.21.22) ...
Selecting previously unselected package linux-headers-4.4.0-28.
Preparing to unpack .../linux-headers-4.4.0-28_4.4.0-28.47_all.deb ...
Unpacking linux-headers-4.4.0-28 (4.4.0-28.47) ...
Selecting previously unselected package linux-headers-4.4.0-28-generic.
Preparing to unpack .../linux-headers-4.4.0-28-generic_4.4.0-28.47_amd64.deb ...
Unpacking linux-headers-4.4.0-28-generic (4.4.0-28.47) ...
Preparing to unpack .../linux-headers-generic_4.4.0.28.30_amd64.deb ...
Unpacking linux-headers-generic (4.4.0.28.30) over (4.4.0.21.22) ...
Setting up linux-image-4.4.0-28-generic (4.4.0-28.47) ...
Running depmod.
update-initramfs: deferring update (hook will be called later)
Examining /etc/kernel/postinst.d.
run-parts: executing /etc/kernel/postinst.d/apt-auto-removal 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/initramfs-tools 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
update-initramfs: Generating /boot/initrd.img-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/pm-utils 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/unattended-upgrades 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/update-notifier 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/zz-update-grub 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
Generating grub configuration file ...
Warning: Setting GRUB_TIMEOUT to a non-zero value when GRUB_HIDDEN_TIMEOUT is set is no longer supported.
Found linux image: /boot/vmlinuz-4.4.0-28-generic
Found initrd image: /boot/initrd.img-4.4.0-28-generic
Found linux image: /boot/vmlinuz-4.4.0-21-generic
Found initrd image: /boot/initrd.img-4.4.0-21-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done
Setting up linux-image-extra-4.4.0-28-generic (4.4.0-28.47) ...
run-parts: executing /etc/kernel/postinst.d/apt-auto-removal 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/initramfs-tools 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
update-initramfs: Generating /boot/initrd.img-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/pm-utils 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/unattended-upgrades 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/update-notifier 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
run-parts: executing /etc/kernel/postinst.d/zz-update-grub 4.4.0-28-generic /boot/vmlinuz-4.4.0-28-generic
Generating grub configuration file ...
Warning: Setting GRUB_TIMEOUT to a non-zero value when GRUB_HIDDEN_TIMEOUT is set is no longer supported.
Found linux image: /boot/vmlinuz-4.4.0-28-generic
Found initrd image: /boot/initrd.img-4.4.0-28-generic
Found linux image: /boot/vmlinuz-4.4.0-21-generic
Found initrd image: /boot/initrd.img-4.4.0-21-generic
Found memtest86+ image: /boot/memtest86+.elf
Found memtest86+ image: /boot/memtest86+.bin
done
Setting up linux-image-generic (4.4.0.28.30) ...
Setting up linux-headers-4.4.0-28 (4.4.0-28.47) ...
Setting up linux-headers-4.4.0-28-generic (4.4.0-28.47) ...
Setting up linux-headers-generic (4.4.0.28.30) ...
Setting up linux-generic (4.4.0.28.30) ...