Set 'dmesg -n [4-6]' in new 'setup' script 007_set_dmesg_level.sh (#3113

)

The new 'setup' stage script setup/default/007_set_dmesg_level.sh
sets 'dmesg -n [4-6]' for the worksflows
recover layoutonly restoreonly finalizeonly mountonly
depending on verbose and debug modes for ReaR.
This is related to #3108

usr/share/rear/setup/default/007_set_dmesg_level.sh

@@ -0,0 +1,45 @@
+
+# This file is part of Relax-and-Recover, licensed under the GNU General
+# Public License. Refer to the included COPYING for full text of license.
+
+# In the ReaR recovery system /etc/scripts/boot calls hardcoded 'dmesg -n 5'
+# to limit console logging for kernel messages to level 5 during recovery system startup
+# (the usual default shows too many kernel messages that disturb the intended ReaR messages)
+# so that kernel error and warning messages appear (intermixed with ReaR messages) on the console
+# so the user can notice when things go wrong in kernel area which helps to understand problems,
+# see https://github.com/rear/rear/issues/3107
+# and https://github.com/rear/rear/pull/3108
+
+# Additionally call 'dmesg -n [4-6]' here depending on verbose and debug modes for ReaR
+# if we are inside the ReaR recovery system (we must not change 'dmesg' on the original system),
+# see https://github.com/rear/rear/issues/3107#issuecomment-1855797222
+test "$RECOVERY_MODE" || return 0
+
+# Now we are inside the ReaR recovery system
+# and 'setup' stage scripts are only run by the following workflows
+# recover layoutonly restoreonly finalizeonly mountonly
+# see https://github.com/rear/rear/pull/3112#issuecomment-1862770147
+# so for those workflows 'dmesg -n [4-6]' is set depending on verbose and debug modes for ReaR.
+# The remaining workflows that can run within the recovery system
+# (cf. init/default/050_check_rear_recover_mode.sh)
+# are opaladmin and help which run with 'dmesg -n 5' from /etc/scripts/boot
+
+# Set minimum dmesg level 4 to show at least kernel error conditions and more severe issues on the console
+local dmesg_level=4
+# In verbose and debug mode increase dmesg level to 5 to also show kernel warnings on the console
+# (kernel warning messages are usually needed because some errors are reported as warnings)
+# and because 'rear recover' is always verbose this matches what is set in /etc/scripts/boot
+test "$VERBOSE" && dmesg_level=5
+# In debugscript mode increase dmesg level to 6 to also show significant kernel conditions
+test "$DEBUGSCRIPTS" && dmesg_level=6
+# dmesg level 7 shows lots of informational kernel messages
+# that are normally not helpful for debugging issues during 'rear recover'
+# see https://github.com/rear/rear/pull/3112#issue-2048550351
+# and dmesg level 8 (kernel debug-level messages) is over the top for 'rear recover'
+# see https://github.com/rear/rear/issues/3107#issuecomment-1855831572
+# and if 'dmesg -n 7' (or something else) is needed it can be called via PRE_RECOVERY_COMMANDS
+# (therefore this script must run before setup/default/010_pre_recovery_script.sh)
+# so what we set here is only the default behaviour
+DebugPrint "Setting dmesg level $dmesg_level"
+dmesg -n $dmesg_level
+