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

[Alexey Gladkov <gladkov.alexey@gmail.com>]

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

> 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.

>  	[ ! -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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-- 
Rgrds, legion