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:

0: halt the computer
1: single-user mode
2: reserved for customization, otherwise the same as 3
3: multi-user mode with networking
4: reserved for customization, otherwise the same as 3
5: same as 4, it is usually used for GUI login (like GNOME's gdm or LXDE's lxdm)
6: reboot the computer

[Note]

Note

Classically, run level 2 above was defined as "multi-user mode without networking", but this was only the case many years ago when multiple users could connect to a system via serial ports. In today's environment it makes no sense, and we now say it is "reserved".

9.6.2. Configuring Sysvinit

During kernel initialization, the first program that is run (if not overridden on the command line) is init. This program reads the initialization file /etc/inittab. Create this file with:

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

An explanation of this initialization file is in the man page for inittab. In LFS, the key command is rc. The initialization file above instructs rc to run all the scripts starting with an S in the /etc/rc.d/rcS.d directory followed by all the scripts starting with an S in the /etc/rc.d/rc?.d directory where the question mark is specified by the initdefault value.

As a convenience, the rc script reads a library of functions in /lib/lsb/init-functions. This library also reads an optional configuration file, /etc/sysconfig/rc.site. Any of the system configuration parameters described in subsequent sections can be placed in this file, allowing consolidation of all system parameters in this one file.

As a debugging convenience, the functions script also logs all output to /run/var/bootlog. Since the /run directory is a tmpfs, this file is not persistent across boots; however, it is appended to the more permanent file /var/log/boot.log at the end of the boot process.

9.6.2.1. Changing Run Levels

Changing run levels is done with init <runlevel>, where <runlevel> is the target run level. For example, to reboot the computer, a user could issue the init 6 command, which is an alias for the reboot command. Likewise, init 0 is an alias for the halt command.

There are a number of directories under /etc/rc.d that look like rc?.d (where ? is the number of the run level) and rcS.d, all containing a number of symbolic links. Some links begin with a K; the others begin with an S, and all of them have two numbers following the initial letter. The K means to stop (kill) a service and the S means to start a service. The numbers determine the order in which the scripts are run, from 00 to 99—the smaller the number, the sooner the script runs. When init switches to another run level, the appropriate services are either started or stopped, depending on the run level chosen.

The real scripts are in /etc/rc.d/init.d. They do the actual work, and the symlinks all point to them. K links and S links point to the same script in /etc/rc.d/init.d. This is because the scripts can be called with different parameters like start, stop, restart, reload, and status. When a K link is encountered, the appropriate script is run with the stop argument. When an S link is encountered, the appropriate script is run with the start argument.

These are descriptions of what the arguments make the scripts do:

start

The service is started.

stop

The service is stopped.

restart

The service is stopped and then started again.

reload

The configuration of the service is updated. This is used after the configuration file of a service was modified, when the service does not need to be restarted.

status

Tells if the service is running and with which PIDs.

Feel free to modify the way the boot process works (after all, it is your own LFS system). The files given here are an example of how it can be done.

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.

[Note]

Note

The CLOCKPARAMS and UTC parameters may also be set in the /etc/sysconfig/rc.site file.

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:

LOGLEVEL

This variable specifies the log level for kernel messages sent to the console as set by dmesg -n. Valid levels are from "1" (no messages) to "8". The default level is "7".

KEYMAP

This variable specifies the arguments for the loadkeys program, typically, the name of the keymap to load, e.g., it. If this variable is not set, the bootscript will not run the loadkeys program, and the default kernel keymap will be used. Note that a few keymaps have multiple versions with the same name (cz and its variants in qwerty/ and qwertz/, es in olpc/ and qwerty/, and trf in fgGIod/ and qwerty/). In these cases the parent directory should also be specified (e.g. qwerty/es) to ensure the proper keymap is loaded.

KEYMAP_CORRECTIONS

This (rarely used) variable specifies the arguments for the second call to the loadkeys program. This is useful if the stock keymap is not completely satisfactory and a small adjustment has to be made. E.g., to include the Euro sign into a keymap that normally doesn't have it, set this variable to euro2.

FONT

This variable specifies the arguments for the setfont program. Typically, this includes the font name, -m, and the name of the application character map to load. E.g., in order to load the lat1-16 font together with the 8859-1 application character map (appropriate in the USA), set this variable to lat1-16 -m 8859-1. In UTF-8 mode, the kernel uses the application character map to convert 8-bit key codes to UTF-8. Therefore the argument of the "-m" parameter should be set to the encoding of the composed key codes in the keymap.

UNICODE

Set this variable to 1, yes, or true in order to put the console into UTF-8 mode. This is useful in UTF-8 based locales and harmful otherwise.

LEGACY_CHARSET

For many keyboard layouts, there is no stock Unicode keymap in the Kbd package. The console bootscript will convert an available keymap to UTF-8 on the fly if this variable is set to the encoding of the available non-UTF-8 keymap.

Some examples:

  • For a non-Unicode setup, only the KEYMAP and FONT variables are generally needed. E.g., for a Polish setup, one would use:

    cat > /etc/sysconfig/console << "EOF"
    # Begin /etc/sysconfig/console
    
    KEYMAP="pl2"
    FONT="lat2a-16 -m 8859-2"
    
    # End /etc/sysconfig/console
    EOF
  • As mentioned above, it is sometimes necessary to adjust a stock keymap slightly. The following example adds the Euro symbol to the German keymap:

    cat > /etc/sysconfig/console << "EOF"
    # Begin /etc/sysconfig/console
    
    KEYMAP="de-latin1"
    KEYMAP_CORRECTIONS="euro2"
    FONT="lat0-16 -m 8859-15"
    UNICODE="1"
    
    # End /etc/sysconfig/console
    EOF
  • The following is a Unicode-enabled example for Bulgarian, where a stock UTF-8 keymap exists:

    cat > /etc/sysconfig/console << "EOF"
    # Begin /etc/sysconfig/console
    
    UNICODE="1"
    KEYMAP="bg_bds-utf8"
    FONT="LatArCyrHeb-16"
    
    # End /etc/sysconfig/console
    EOF
  • Due to the use of a 512-glyph LatArCyrHeb-16 font in the previous example, bright colors are no longer available on the Linux console unless a framebuffer is used. If one wants to have bright colors without a framebuffer and can live without characters not belonging to his language, it is still possible to use a language-specific 256-glyph font, as illustrated below:

    cat > /etc/sysconfig/console << "EOF"
    # Begin /etc/sysconfig/console
    
    UNICODE="1"
    KEYMAP="bg_bds-utf8"
    FONT="cyr-sun16"
    
    # End /etc/sysconfig/console
    EOF
  • The following example illustrates keymap autoconversion from ISO-8859-15 to UTF-8 and enabling dead keys in Unicode mode:

    cat > /etc/sysconfig/console << "EOF"
    # Begin /etc/sysconfig/console
    
    UNICODE="1"
    KEYMAP="de-latin1"
    KEYMAP_CORRECTIONS="euro2"
    LEGACY_CHARSET="iso-8859-15"
    FONT="LatArCyrHeb-16 -m 8859-15"
    
    # End /etc/sysconfig/console
    EOF
  • Some keymaps have dead keys (i.e., keys that don't produce a character by themselves, but put an accent on the character produced by the next key) or define composition rules (such as: press Ctrl+. A E to get in the default keymap). Linux-6.5.1 interprets dead keys and composition rules in the keymap correctly only when the source characters to be composed together are not multibyte. This deficiency doesn't affect keymaps for European languages, because there accents are added to unaccented ASCII characters, or two ASCII characters are composed together. However, in UTF-8 mode it is a problem; e.g., for the Greek language, where one sometimes needs to put an accent on the letter alpha. The solution is either to avoid the use of UTF-8, or to install the X window system, which doesn't have this limitation, in its input handling.

  • For Chinese, Japanese, Korean, and some other languages, the Linux console cannot be configured to display the needed characters. Users who need such languages should install the X Window System, fonts that cover the necessary character ranges, and the proper input method (e.g., SCIM supports a wide variety of languages).

[Note]

Note

The /etc/sysconfig/console file only controls the Linux text console localization. It has nothing to do with setting the proper keyboard layout and terminal fonts in the X Window System, with ssh sessions, or with a serial console. In such situations, limitations mentioned in the last two list items above do not apply.

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=

9.6.8.1. Customizing the Boot and Shutdown Scripts

The LFS boot scripts boot and shut down a system in a fairly efficient manner, but there are a few tweaks you can make in the rc.site file to improve speed even more, and to adjust messages according to your preferences. To do this, adjust the settings in the /etc/sysconfig/rc.site file above.

  • During the boot script udev, there is a call to udev settle that requires some time to complete. This time may or may not be required depending on the devices in the system. If you only have simple partitions and a single ethernet card, the boot process will probably not need to wait for this command. To skip it, set the variable OMIT_UDEV_SETTLE=y.

  • The boot script udev_retry also runs udev settle by default. This command is only needed if the /var directory is separately mounted, because the clock needs the /var/lib/hwclock/adjtime file. Other customizations may also need to wait for udev to complete, but in many installations it is not necessary. Skip the command by setting the variable OMIT_UDEV_RETRY_SETTLE=y.

  • By default, the file system checks are silent. This can appear to be a delay during the bootup process. To turn on the fsck output, set the variable VERBOSE_FSCK=y.

  • When rebooting, you may want to skip the filesystem check, fsck, completely. To do this, either create the file /fastboot or reboot the system with the command /sbin/shutdown -f -r now. On the other hand, you can force all file systems to be checked by creating /forcefsck or running shutdown with the -F parameter instead of -f.

    Setting the variable FASTBOOT=y will disable fsck during the boot process until it is removed. This is not recommended on a permanent basis.

  • Normally, all files in the /tmp directory are deleted at boot time. Depending on the number of files or directories present, this can cause a noticeable delay in the boot process. To skip removing these files set the variable SKIPTMPCLEAN=y.

  • During shutdown, the init program sends a TERM signal to each program it has started (e.g. agetty), waits for a set time (default 3 seconds), then sends each process a KILL signal and waits again. This process is repeated in the sendsignals script for any processes that are not shut down by their own scripts. The delay for init can be set by passing a parameter. For example to remove the delay in init, pass the -t0 parameter when shutting down or rebooting (e.g. /sbin/shutdown -t0 -r now). The delay for the sendsignals script can be skipped by setting the parameter KILLDELAY=0.