9.6. System V Bootscript Usage and Configuration

9.6.1. How Do the System V Bootscripts Work?

This version of LFS uses a special booting facility named SysVinit, based on a series of run levels. The boot procedure can be quite different from one system to another; the fact that things worked one way in a particular Linux distribution does not guarantee they will work the same way in LFS. LFS has its own way of doing things, but it does respect generally accepted standards.

There is an alternative boot procedure called systemd. We will not discuss that boot process any further here. For a detailed description visit https://www.linux.com/training-tutorials/understanding-and-using-systemd/.

SysVinit (which will be referred to as “init” from now on) uses a run levels scheme. There are seven run levels, numbered 0 to 6. (Actually, there are more run levels, but the others are for special cases and are generally not used. See init(8) for more details.) Each one of the seven corresponds to actions the computer is supposed to perform when it starts up or shuts down. The default run level is 3. Here are the descriptions of the different run levels as they are implemented in LFS:

cat > /etc/inittab << "EOF"
# Begin /etc/inittab

id:3:initdefault:

si::sysinit:/etc/rc.d/init.d/rc S

l0:0:wait:/etc/rc.d/init.d/rc 0
l1:S1:wait:/etc/rc.d/init.d/rc 1
l2:2:wait:/etc/rc.d/init.d/rc 2
l3:3:wait:/etc/rc.d/init.d/rc 3
l4:4:wait:/etc/rc.d/init.d/rc 4
l5:5:wait:/etc/rc.d/init.d/rc 5
l6:6:wait:/etc/rc.d/init.d/rc 6

ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now

su:S06:once:/sbin/sulogin
s1:1:respawn:/sbin/sulogin

1:2345:respawn:/sbin/agetty --noclear tty1 9600
2:2345:respawn:/sbin/agetty tty2 9600
3:2345:respawn:/sbin/agetty tty3 9600
4:2345:respawn:/sbin/agetty tty4 9600
5:2345:respawn:/sbin/agetty tty5 9600
6:2345:respawn:/sbin/agetty tty6 9600

# End /etc/inittab
EOF

9.6.3. Udev Bootscripts

The /etc/rc.d/init.d/udev initscript starts udevd, triggers any "coldplug" devices that have already been created by the kernel, and waits for any rules to complete. The script also unsets the uevent handler from the default of /sbin/hotplug . This is done because the kernel no longer needs to call an external binary. Instead, udevd will listen on a netlink socket for uevents that the kernel raises.

The /etc/rc.d/init.d/udev_retry script takes care of re-triggering events for subsystems whose rules may rely on file systems that are not mounted until the mountfs script is run (in particular, /usr and /var may cause this). This script runs after the mountfs script, so those rules (if re-triggered) should succeed the second time around. It is configured by the /etc/sysconfig/udev_retry file; any words in this file other than comments are considered subsystem names to trigger at retry time. To find the subsystem of a device, use udevadm info --attribute-walk <device> where <device> is an absolute path in /dev or /sys, such as /dev/sr0, or /sys/class/rtc.

For information on kernel module loading and udev, see Section 9.3.2.3, “Module Loading”.

9.6.4. Configuring the System Clock

The setclock script reads the time from the hardware clock, also known as the BIOS or Complementary Metal Oxide Semiconductor (CMOS) clock. If the hardware clock is set to UTC, this script will convert the hardware clock's time to the local time using the /etc/localtime file (which tells the hwclock program which time zone to use). There is no way to detect whether or not the hardware clock is set to UTC, so this must be configured manually.

The setclock program is run via udev when the kernel detects the hardware capability upon boot. It can also be run manually with the stop parameter to store the system time to the CMOS clock.

If you cannot remember whether or not the hardware clock is set to UTC, find out by running the hwclock --localtime --show command. This will display what the current time is according to the hardware clock. If this time matches whatever your watch says, then the hardware clock is set to local time. If the output from hwclock is not local time, chances are it is set to UTC time. Verify this by adding or subtracting the proper number of hours for your time zone to the time shown by hwclock. For example, if you are currently in the MST time zone, which is also known as GMT -0700, add seven hours to the local time.

Change the value of the UTC variable below to a value of 0 (zero) if the hardware clock is NOT set to UTC time.

Create a new file /etc/sysconfig/clock by running the following:

cat > /etc/sysconfig/clock << "EOF"
# Begin /etc/sysconfig/clock

UTC=1

# Set this to any options you might need to give to hwclock,
# such as machine hardware clock type for Alphas.
CLOCKPARAMS=

# End /etc/sysconfig/clock
EOF

A good hint explaining how to deal with time on LFS is available at https://www.linuxfromscratch.org/hints/downloads/files/time.txt. It explains issues such as time zones, UTC, and the TZ environment variable.

9.6.5. Configuring the Linux Console

This section discusses how to configure the console bootscript that sets up the keyboard map, console font, and console kernel log level. If non-ASCII characters (e.g., the copyright sign, the British pound sign, and the Euro symbol) will not be used and the keyboard is a U.S. one, much of this section can be skipped. Without the configuration file, (or equivalent settings in rc.site), the console bootscript will do nothing.

The console script reads the /etc/sysconfig/console file for configuration information. Decide which keymap and screen font will be used. Various language-specific HOWTOs can also help with this; see https://tldp.org/HOWTO/HOWTO-INDEX/other-lang.html. If still in doubt, look in the /usr/share/keymaps and /usr/share/consolefonts directories for valid keymaps and screen fonts. Read the loadkeys(1) and setfont(8) manual pages to determine the correct arguments for these programs.

The /etc/sysconfig/console file should contain lines of the form: VARIABLE="value". The following variables are recognized:

Some examples:

9.6.6. Creating Files at Boot

At times, it is desirable to create files at boot time. For instance, the /tmp/.ICE-unix directory is often needed. This can be done by creating an entry in the /etc/sysconfig/createfiles configuration script. The format of this file is embedded in the comments of the default configuration file.

9.6.7. Configuring the Sysklogd Script

The sysklogd script invokes the syslogd program as a part of System V initialization. The -m 0 option turns off the periodic timestamp mark that syslogd writes to the log files every 20 minutes by default. If you want to turn on this periodic timestamp mark, edit /etc/sysconfig/rc.site and define the variable SYSKLOGD_PARMS to the desired value. For instance, to remove all parameters, set the variable to a null value:

SYSKLOGD_PARMS=

See man syslogd for more options.

9.6.8. The rc.site File

The optional /etc/sysconfig/rc.site file contains settings that are automatically set for each SystemV boot script. It can alternatively set the values specified in the hostname, console, and clock files in the /etc/sysconfig/ directory. If the associated variables are present in both these separate files and rc.site, the values in the script-specific files take effect.

rc.site also contains parameters that can customize other aspects of the boot process. Setting the IPROMPT variable will enable selective running of bootscripts. Other options are described in the file comments. The default version of the file is as follows:

# rc.site
# Optional parameters for boot scripts.

# Distro Information
# These values, if specified here, override the defaults
#DISTRO="Linux From Scratch" # The distro name
#DISTRO_CONTACT="lfs-dev@lists.linuxfromscratch.org" # Bug report address
#DISTRO_MINI="LFS" # Short name used in filenames for distro config

# Define custom colors used in messages printed to the screen

# Please consult `man console_codes` for more information
# under the "ECMA-48 Set Graphics Rendition" section
#
# Warning: when switching from a 8bit to a 9bit font,
# the linux console will reinterpret the bold (1;) to
# the top 256 glyphs of the 9bit font.  This does
# not affect framebuffer consoles

# These values, if specified here, override the defaults
#BRACKET="\\033[1;34m" # Blue
#FAILURE="\\033[1;31m" # Red
#INFO="\\033[1;36m"    # Cyan
#NORMAL="\\033[0;39m"  # Grey
#SUCCESS="\\033[1;32m" # Green
#WARNING="\\033[1;33m" # Yellow

# Use a colored prefix
# These values, if specified here, override the defaults
#BMPREFIX="      "
#SUCCESS_PREFIX="${SUCCESS}  *  ${NORMAL} "
#FAILURE_PREFIX="${FAILURE}*****${NORMAL} "
#WARNING_PREFIX="${WARNING} *** ${NORMAL} "

# Manually set the right edge of message output (characters)
# Useful when resetting console font during boot to override
# automatic screen width detection
#COLUMNS=120

# Interactive startup
#IPROMPT="yes" # Whether to display the interactive boot prompt
#itime="3"    # The amount of time (in seconds) to display the prompt

# The total length of the distro welcome string, without escape codes
#wlen=$(echo "Welcome to ${DISTRO}" | wc -c )
#welcome_message="Welcome to ${INFO}${DISTRO}${NORMAL}"

# The total length of the interactive string, without escape codes
#ilen=$(echo "Press 'I' to enter interactive startup" | wc -c )
#i_message="Press '${FAILURE}I${NORMAL}' to enter interactive startup"

# Set scripts to skip the file system check on reboot
#FASTBOOT=yes

# Skip reading from the console
#HEADLESS=yes

# Write out fsck progress if yes
#VERBOSE_FSCK=no

# Speed up boot without waiting for settle in udev
#OMIT_UDEV_SETTLE=y

# Speed up boot without waiting for settle in udev_retry
#OMIT_UDEV_RETRY_SETTLE=yes

# Skip cleaning /tmp if yes
#SKIPTMPCLEAN=no

# For setclock
#UTC=1
#CLOCKPARAMS=

# For consolelog (Note that the default, 7=debug, is noisy)
#LOGLEVEL=7

# For network
#HOSTNAME=mylfs

# Delay between TERM and KILL signals at shutdown
#KILLDELAY=3

# Optional sysklogd parameters
#SYSKLOGD_PARMS="-m 0"

# Console parameters
#UNICODE=1
#KEYMAP="de-latin1"
#KEYMAP_CORRECTIONS="euro2"
#FONT="lat0-16 -m 8859-15"
#LEGACY_CHARSET=