WIP: Log stage-{1,2} output to secondary consoles

nixos/modules/system/boot/stage-1-init.sh

@@ -1,7 +1,6 @@
 #! @shell@
 
 targetRoot=/mnt-root
-console=tty1
 
 extraUtils="@extraUtils@"
 export LD_LIBRARY_PATH=@extraUtils@/lib
@@ -24,6 +23,15 @@ fail() {
 
     @preFailCommands@
 
+    # Figure out a console device to use for the interactive shell.
+    # Plain /dev/console isn't good because terminal size queries don't work (useful for e.g. less).
+    # Same approach is taken by Debian's initramfs-tools and dracut.
+    console=$(cat /proc/consoles | head -n1 | cut -d' ' -f1)
+    if [ "$console" = tty0 ] || [ -z "$console" ]; then
+        # tty0 is a pseudo-console representing the current VT, replace that with a specific VT.
+        console=tty1
+    fi
+
     # If starting stage 2 failed, allow the user to repair the problem
     # in an interactive shell.
     cat <<EOF
@@ -112,34 +120,34 @@ specialMount() {
 }
 source @earlyMountScript@
 
-# Log the script output to /dev/kmsg or /run/log/stage-1-init.log.
-mkdir -p /tmp
+# Extract the list of secondary consoles from kernel. /sys/class/tty/console/active contains a list
+# of all the active consoles, from which we filter out the primary console (the last one in the file).
+# See https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-tty.
+secondaryConsoles="$(cat /sys/class/tty/console/active | sed -e 's/[^ ]*$//')"
+
+# Log the script output to either /dev/kmsg or /run/log/stage-1-init.log and to all secondary consoles.
+mkdir -p /tmp /run/log
 mkfifo /tmp/stage-1-init.log.fifo
 logOutFd=8 && logErrFd=9
 eval "exec $logOutFd>&1 $logErrFd>&2"
-if test -w /dev/kmsg; then
-    tee -i < /tmp/stage-1-init.log.fifo /proc/self/fd/"$logOutFd" | while read -r line; do
-        if test -n "$line"; then
-            echo "<7>stage-1-init: $line" > /dev/kmsg
-        fi
-    done &
-else
-    mkdir -p /run/log
-    tee -i < /tmp/stage-1-init.log.fifo /run/log/stage-1-init.log &
-fi
+tee -i < /tmp/stage-1-init.log.fifo /proc/self/fd/"$logOutFd" | while read -r line; do
+    if test -w /dev/kmsg; then
+        echo "<7>stage-1-init: $line" > /dev/kmsg
+    else
+        echo "$line" >> /run/log/stage-1-init.log
+    fi
+
+    for c in $secondaryConsoles; do
+        echo "$line" >> "/dev/$c"
+    done
+done &
 exec > /tmp/stage-1-init.log.fifo 2>&1
 
 
 # Process the kernel command line.
 export stage2Init=/init
 for o in $(cat /proc/cmdline); do
     case $o in
-        console=*)
-            set -- $(IFS==; echo $o)
-            params=$2
-            set -- $(IFS=,; echo $params)
-            console=$1
-            ;;
         init=*)
             set -- $(IFS==; echo $o)
             stage2Init=$2

nixos/modules/system/boot/stage-2-init.sh

@@ -81,7 +81,7 @@ ln -s /proc/mounts /etc/mtab
 [ -e /proc/bus/usb ] && mount -t usbfs usbfs /proc/bus/usb # UML doesn't have USB by default
 install -m 01777 -d /tmp
 install -m 0755 -d /var/{log,lib,db} /nix/var /etc/nixos/ \
-    /run/lock /home /bin # for the /bin/sh symlink
+    /run/lock /run/log /home /bin # for the /bin/sh symlink
 
 
 # Miscellaneous boot time cleanup.
@@ -110,19 +110,30 @@ if [ -n "@useHostResolvConf@" ] && [ -e /etc/resolv.conf ]; then
     resolvconf -m 1000 -a host </etc/resolv.conf
 fi
 
-# Log the script output to /dev/kmsg or /run/log/stage-2-init.log.
+
+# Extract the list of secondary consoles from kernel. /sys/class/tty/console/active contains a list
+# of all the active consoles, from which we filter out the primary console (the last one in the file).
+# See https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-tty.
+# Except don't do this inside a container, as apparently at least LXC doesn't contain them from the host.
+secondaryConsoles=""
+if [ -z "$container" ]; then
+    secondaryConsoles="$(cat /sys/class/tty/console/active | sed -e 's/[^ ]*$//')"
+fi
+
+# Log the script output to /dev/kmsg or /run/log/stage-2-init.log and to all secondary consoles.
 # Only at this point are all the necessary prerequisites ready for these commands.
 exec {logOutFd}>&1 {logErrFd}>&2
-if test -w /dev/kmsg; then
-    exec > >(tee -i /proc/self/fd/"$logOutFd" | while read -r line; do
-        if test -n "$line"; then
-            echo "<7>stage-2-init: $line" > /dev/kmsg
-        fi
-    done) 2>&1
-else
-    mkdir -p /run/log
-    exec > >(tee -i /run/log/stage-2-init.log) 2>&1
-fi
+exec > >(tee -i /proc/self/fd/"$logOutFd" | while read -r line; do
+    if test -w /dev/kmsg; then
+        echo "<7>stage-2-init: $line" > /dev/kmsg
+    else
+        echo "$line" >> /run/log/stage-2-init.log
+    fi
+
+    for c in $secondaryConsoles; do
+        echo "$line" >> "/dev/$c"
+    done
+done) 2>&1
 
 
 # Run the script that performs all configuration activation that does

nixos/modules/system/boot/stage-2.nix

@@ -17,6 +17,7 @@ let
     inherit (config.system.build) earlyMountScript;
     path = lib.makeBinPath [
       pkgs.coreutils
+      pkgs.gnused
       pkgs.utillinux
       pkgs.openresolv
     ];