Re: [make-initrd] [PATCH v6 21/22] bootchain-core: adds ability to bring the daemon to the foreground

[Leonid Krivoshein <klark.devel@gmail.com>]

26.10.2021 22:16, Alexey Gladkov пишет:
> On Sun, Oct 24, 2021 at 08:23:23PM +0300, Leonid Krivoshein wrote:
>> Also introduces configuration parameter BC_FGVT_ACTIVATE and new pseudo-step
>> "fg". This is only works together with the "bootchain-interactive" feature
>> included to initramfs. Jointly features "bootchain-core" and "bootchain-
>> interactive" they lay the foundation for building simple text installers
>> in the stage1.
> Напомни пожалуйста, а что мешает демону из бэкграунда писать на указанный
> терминал и читать с него ?
>
> Типа вот так:
>
> exec </dev/tty2 >/dev/tty2 2>&1

Там ровно этот код и отрабатывает. Суть усложнения концепции заключалась 
в другом: хотелось получить выделенный интерактивный терминал с 
диалогами, отличный от tty1, и активировать его, при необходимости, по 
таймауту или сразу. Чтобы быстрый процесс загрузки не мелькал перед 
глазами, если в этом нет необходимости. И чтобы вывод демонов 
make-initrd не смешивался на tty1 с диалогами.

Переход в интерактивный режим был разделён на две части: IM_exec() и 
IM_activate() подобно тому, как приложения запускаются в NIX-системах 
через fork() и exec(). Исходно запущенный демон запускает 
вспомогательный терминал для отладки и есть код, который ждёт его 
завершения. Изначально демон был вообще разделён на две части, 
перезапускалась только вторая часть. Причина -- в использовании openvt 
... так как другие варианты не подходили.

Алексей Шепляков предложил тут хорошую идею: использовать для тех же 
целей screen или tmux. Собственно задача: восстановить после себя 
консоль. Вариант идеальный, но у меня пока не вышло из-за проблем с 
настройкой utf8 в stage1, там одно другое цепляет, есть конфликты с 
plymouth и kbd, который сейчас, кажется, совсем нерабочий. Так что 
переключение на другие консоли через openvt -- пока единственная 
рабочая, но не лучшая реализация, надо обсудить, как это улучшить, не 
меняя API.


>
>> See README.md for more details.
>>
>> Signed-off-by: Leonid Krivoshein <klark.devel@gmail.com>
>> ---
>>   features/bootchain-core/README.md             | 16 +++++++
>>   .../data/bin/bootchain-sh-functions           |  2 +
>>   features/bootchain-core/data/sbin/chaind      | 45 ++++++++++++++++---
>>   3 files changed, 58 insertions(+), 5 deletions(-)
>>
>> diff --git a/features/bootchain-core/README.md b/features/bootchain-core/README.md
>> index ab89181..943b4b0 100644
>> --- a/features/bootchain-core/README.md
>> +++ b/features/bootchain-core/README.md
>> @@ -50,11 +50,18 @@ us to optimize fill in `initramfs` only which we are need.
>>   
>>   - Modularity: loading methods are initially separated from the common
>>     code and daemon.
>> +- Provides the ability to bring the daemon to the foreground at any time. This
>> +  restarts the `chaind` process on a specific terminal, although initially the
>> +  daemon is started in the background.
>>   - Some steps (actions) are built directly into the code of the main loop
>>     of the `chaind` daemon, external scripts are not called to execute them.
>>     Such pseudo-steps allow you to control, basically, the internal state of the
>>     daemon and should not be taken into account in the boot chain, as if they are
>>     hidden.
>> +- Optionally, the daemon can work in conjunction with the `bootchain-interactive`
>> +  feature, can move to the foreground and continue working on a specific terminal,
>> +  by default, tty2. Jointly features `bootchain-core` and `bootchain-interactive`
>> +  they lay the foundation for building simple text installers in stage1.
>>   - The `chaind` daemon allows you to overload the chain with a new set of steps,
>>     thanks to this, you can change the logic of work "on the fly", support loops
>>     and conditional jumps, in text dialogs it is an opportunity to go back.
>> @@ -147,6 +154,11 @@ parameters:
>>     should be output in the background. By default, the value is 3, respectively,
>>     the log is output to tty3. An empty value allows you to disable log output
>>     to any terminal.
>> +- `BC_FGVT_ACTIVATE` - delay in seconds before activating the interactive
>> +  terminal, by default tty2 is activated after 2 seconds in debug mode
>> +  or after 8 seconds in normal mode. An empty value instructs to activate
>> +  the interactive terminal immediately. This configuration option only works
>> +  together with the `bootchain-interactive` features included in initramfs.
>>   - `BC_LOGFILE` - the full path to the log file or the name of a special device,
>>     to which debugging messages will be output. In NATIVE mode, the default value
>>     is `/var/log/chaind.log`, in COMPATIBILITY mode with `pipeline` the default
>> @@ -165,6 +177,10 @@ embedded in the code of the main loop of the `boot chain-loop` daemon, do
>>   not need additional parameters and should not be taken into account when
>>   addressing, as if they are hidden.
>>   
>> +- `fg` - provides the transfer of the daemon to interactive mode when building
>> +  initramfs with `bootchain-interactive` features. The `bootchain-core` itself
>> +  is not interactivity required, but some other steps may need it, such as
>> +  `altboot`.
>>   - `noop` - does not perform any actions and is designed to pull off the results
>>     on the <OUT> of the previous step from the <IN> of the next step, which can
>>     be useful, for example, when we don`t want the results of the `waitdev` step
>> diff --git a/features/bootchain-core/data/bin/bootchain-sh-functions b/features/bootchain-core/data/bin/bootchain-sh-functions
>> index 3a9ec6b..743a8f9 100644
>> --- a/features/bootchain-core/data/bin/bootchain-sh-functions
>> +++ b/features/bootchain-core/data/bin/bootchain-sh-functions
>> @@ -25,6 +25,8 @@ else
>>   	pipeline_mode=
>>   fi
>>   
>> +[ -n "$BC_DEBUG" ] && BC_FGVT_ACTIVATE=1 ||
>> +	BC_FGVT_ACTIVATE="${BC_FGVT_ACTIVATE:-7}"
>>   BC_NEXTCHAIN=/.initrd/bootchain/bootchain.next
>>   BC_PASSED=/.initrd/bootchain/passed
>>   handlerdir=/lib/bootchain
>> diff --git a/features/bootchain-core/data/sbin/chaind b/features/bootchain-core/data/sbin/chaind
>> index e8ce94a..68a1aae 100755
>> --- a/features/bootchain-core/data/sbin/chaind
>> +++ b/features/bootchain-core/data/sbin/chaind
>> @@ -2,11 +2,12 @@
>>   
>>   . bootchain-sh-functions
>>   
>> -bcretry=1
>> +bcretry="${bcretry:-1}"
>>   pidfile="/var/run/$PROG.pid"
>> -chainsteps="$BOOTCHAIN"
>> -stepnum=0
>> -prevdir=
>> +chainsteps="${chainsteps-}"
>> +stepnum="${stepnum:-0}"
>> +prevdir="${prevdir-}"
>> +BC_IM_supported=
>>   
>>   
>>   exit_handler()
>> @@ -25,6 +26,8 @@ debug()
>>   }
>>   
>>   
>> +# Only when daemon started first time
>> +if [ "x${1-}" != "x--foreground" ]; then
> "x" тут признак чего ? не надо этого.

Признак Debian-way! :-) Ну, я боялся, что в этом месте "--" может быть 
не так истолковано.


>>   	[ ! -f "$pidfile" ] ||
>>   		fatal "already running"
>>   	set_cleanup_handler exit_handler
>> @@ -57,12 +60,44 @@ debug()
>>   	mountpoint -q -- "$mntdir" ||
>>   		run mount -t tmpfs tmpfs "$mntdir" ||:
>>   
>> +	chainsteps="$BOOTCHAIN"
>> +fi
>> +
>> +# Check that interactive mode supports
>> +if has_feature bootchain-interactive; then
>> +	. interactive-sh-functions
>> +
>> +	[ "x${1-}" != "x--foreground" ] ||
>> +		IM_activate "$BC_FGVT_ACTIVATE" "$BC_LOGFILE"
>> +	BC_IM_supported=1
>> +fi
>> +
>>   rc=0
>>   while [ -n "$chainsteps" ]; do
>>   	name="${chainsteps%%,*}"
>>   	exe="$handlerdir/$name"
>>   
>> -	if [ "$name" = noop ]; then
>> +	if [ "$name" = fg ]; then
>> +		[ -n "$BC_IM_supported" ] ||
>> +			fatal "bootchain-interactive feature required"
>> +		assign "callnum" "\${callnum_$name:-0}"
>> +		chainsteps="${chainsteps#$name}"
>> +		chainsteps="${chainsteps#,}"
>> +
>> +		if IM_is_active; then
>> +			message "[$callnum] Step '$name' has ignored"
>> +		else
>> +			message "[$callnum] Switching to foreground"
>> +
>> +			callnum=$((1 + $callnum))
>> +			assign "callnum_$name" "\$callnum"
>> +
>> +			export stepnum chainsteps callnum_fg prevdir bcretry
>> +
>> +			IM_exec "$0" --foreground
>> +		fi
>> +
>> +	elif [ "$name" = noop ]; then
>>   		chainsteps="${chainsteps#$name}"
>>   		chainsteps="${chainsteps#,}"
>>   		prevdir=
>> -- 
>> 2.24.1
>>
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>>

-- 
Best regards,
Leonid Krivoshein.