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boot

Meant to be run as pid 1 as a stage1 init. Performs the necessary early system preparation and execs into scandir start.

Interface

boot [ -h ] [ -z ] [ -m ] [ -s skel ] [ -l log_user ] [ -e environment ] [ -d dev ] [ -b banner ]

This program performs some early preparations, spawns a process that will run the rc.init script and then execs into scandir start.

Exit codes

Command boot never exits. It spawns the rc.init script and execs into scandir start which runs forever until the machine stops or reboots.

Options

  • -h: prints this help.

  • -m: umount the basename of the LIVE directory set into the init.conf skeleton file, if it is already mounted, and mounts a tmpfs on it. By default, the LIVE basename is mounted if it is not already a valid mountpoint. Otherwise without the -m option, it does nothing.

  • -s skel: an absolute path. Directory that holds skeleton files. By default this will be /etc/66. The default can also be changed at compile time by passing the --with-skeleton=DIR option to ./configure. This directory must contain the necessary skeleton files to properly boot the machine, without it the system will not boot.

  • -l log_user: the catch-all logger will run as log_user. Default is root. The default can also be changed at compile-time by passing the --with-s6-log-user=user option to ./configure.

  • -e environment: an absolute path. stage 1 init empties its environment except the PATH variable before spawning the rc.init skeleton file and executing into scandir start in order to prevent kernel environment variables from leaking into the process tree. Then, it import environment from files found at the /etc/66/environment directory (See Environment importation). If you want to define additional environment variables then use this option. Behaves the same as scandir start -e.

  • -d dev: mounts a devtmpfs on dev. By default, no such mount is performed - it is assumed that a devtmpfs is automounted on /dev at boot time by the kernel or an initramfs.

  • -b banner: prints banner to /dev/console at the start of the stage 1 init process. Defaults to: [Starts stage1 process ...]

Early preparation

When booting a system, command boot performs the following operations:

  • It prints a banner to /dev/console.

  • It imports the environment variables. See Environment importation below.

  • It parses the init.conf skeleton file.

  • It chdirs into /.

  • It sets the umask to initial_umask.

  • It becomes a session leader.

  • It mounts a devtmpfs on dev, if requested.

  • It uses /dev/null as its stdin (instead of /dev/console). Although stdout and stderr still use /dev/console for now.

  • It checks if the LIVE basename is a valid mountpoint, and if so it mounts it. If requested, it unmounts if the LIVE basename is a valid mountpoint and performs a mount.

  • It creates the LIVE directory invocating 66 -v VERBOSITY -l LIVE scandir -b -c -s skel create plus -L user_log if requested.

  • It initiates the early services of TREE invocating 66 -v VERBOSITY -l LIVE tree init TREE.

  • It performs "the fifo trick" where it redirects its stdout to the catch-all logger's fifo without blocking before the catch-all logger is even up (because it's a service that will be spawned a bit later, when scandir start is executed).

  • It forks a child, also called stage2.

    • The child is blocked until the catch-all logger runs.

    • The child starts any service of tree TREE.

    • The child becomes a session leader.

  • It also makes the catch-all logger's fifo its stderr.

  • It execs into 66 -v VERBOSITY -l LIVE scandir start with LIVE/scandir/0 (default /run/66/scandir/0) as its scandir.

    • scandir start transitions into s6-svscan which spawns the early services that are defined in TREE where one of those services is scandir-log, which is the catch-all logger. Once this service is up boot's command child stage2 unblocks.

    • The child then execs into rc.init

In the unusual event that any of the above processes fail, command boot will try to launch a single-user login namely sulogin to provide the means to repair the system.

Skeleton files

Skeleton files are mandatory and must exist on your system to be able to boot and shutdown the machine properly. By default those files are installed at /etc/66. Use the --with-skeleton=DIR option at compile time to change it.

  • init : the command boot binary is not meant to be called directly or be linked to the binary directory because it takes command line options. Therefore the init skeleton file is used to pass any options to command boot. By default command boot is launched without options. This file is installed at /usr/bin/init.

  • init.conf : this file contains a set of key=value pairs. All keys are mandatory where the name of the key must not be changed. This is the file available to a user to configure the boot process. By default:

    • VERBOSITY=0 : increases/decreases the verbosity of the stage1 process.

    • LIVE=/run/66 : an absolute path; creates the scandir at LIVE. The value will depend by default on the --livedir=live option set at compile time.

    • PATH=/usr/bin:/usr/sbin:/bin:/sbin:/usr/local/bin : the initial value for the PATH environment variable that will be passed on to all starting processes unless it's overridden by PATH declaration with the -e option. It is absolutely necessary for execline,s6 and all 66 command binaries to be accessible via PATH, else the machine will not boot.

    • TREE=boot : name of the tree to start. This tree should contain a sane set of services to bring up the machine into an operating system. Service marked earlier will start early at the invocation of tree init command. stage2 will then start any other service type. It is the responsibility of the system administrator to build this tree without errors.

    • RCINIT=/etc/66/rc.init : an absolute path. This file is launched at the end of stage1 and run as stage2. It calls tree init command to initiate any enabled services inside of TREE except the earlier ones which were already initiated by stage1. After that it invokes 66 start command to bring up all services.

    • RCSHUTDOWN=/etc/66/rc.shutdown : an absolute path. This is launched when a shutdown is requested also called stage3. It invokes 66 tree stop command to bring down all services of TREE.

    • RCSHUTDOWNFINAL=/etc/66/rc.shutdown.final : an absolute path. This file will be run at the very end of the shutdown procedure, after all processes have been killed and all filesystems have been unmounted, just before the system is rebooted or the power turned off.

    • UMASK=0022 : sets the value of the initial file umask for all starting processes in octal.

    • RESCAN=0 : forces s6-svscan to perform a scan every RESCAN milliseconds. This is an overload function mostly for debugging. It should be 0 during stage1. It is strongly discouraged to set RESCAN to a positive value smaller than 500.

    • CONTAINER=0 : accepted value are 0 or 1 where 0 ask to boot on a hardware system and 1 ask to boot inside a container. Default 0. If set to 1, the rc.init.container file is used instead of the rc.init file.

    • RCINIT_CONTAINER=/etc/66/rc.init.container : an absolute path. This is launched when a boot inside a container is asked. It as the same behavior of the rc.init file but allows to implement a command to run inside this container and retrieves the exit code of that command. The exit code of the command is automatically written at the /etc/66/container/<owner>/halt file modifying the EXITCODE= variable.

    • CATCHLOG=1 : accepted value are 0 or 1 where 0 ask to not redirects its stdout to the catch-all logger's fifo and 1 ask to redirects its stdout to the catch-all logger's fifo. Default 1.

  • rc.init : this file is called by the child of boot command to process stage2. It invokes the commands:

    • 66 -v${VERBOSITY} -l ${LIVE} tree start ${TREE} will initiate and bring up all services marked enabled inside of TREE

    • If this commands fail a warning message is sent to sdtout.

  • rc.init.container : this file replace the rc.init when a boot inside a container is asked. It has the same behavior than the rc.init file. However, this file is especially designed to be used for a boot inside a container. It allow to easily define a command(see comment on that file) to launch inside the container and to retrieve the exit code of that command.

  • rc.shutdown : this file is called at shudown when the administrator requests the halt, poweroff or reboot command. It invokes a single command:

    • 66 -v${VERBOSITY} -l ${LIVE} tree stop -f ${TREE} to bring down all services for all trees marked as enabled.

Kernel command line

Any valid key=value pair set at the init.conf skeleton file can be passed on the kernel command line as parameter:

BOOT_IMAGE=../vmlinuz-linux root=/dev/sda3 ro vga=895 initrd=../intel-ucode.img,../initramfs-linux.img TREE=boot VERBOSITY=4

Environment importation

The environment variables used to launch all commands during the boot process are determined in the following order of precedence. For any key=value pair, the last one encountered takes precedence:

  • Variables imported from the init.conf file.
  • Variables imported from the /etc/66/environment directory.
  • Variables imported from the directory specified with the -e option, if provided.
  • Variables imported from the kernel command line.