From 021fa432447bd7b447ca39738040698db39d751b Mon Sep 17 00:00:00 2001 From: David Oberhollenzer Date: Mon, 5 Nov 2018 15:28:18 +0100 Subject: Initial commit Signed-off-by: David Oberhollenzer --- docs/defconfig.md | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 docs/defconfig.md (limited to 'docs/defconfig.md') diff --git a/docs/defconfig.md b/docs/defconfig.md new file mode 100644 index 0000000..f0a6c86 --- /dev/null +++ b/docs/defconfig.md @@ -0,0 +1,124 @@ +# Default Service Configuration + +## Pseudo Services + +The default configuration contains a number of "pseudo services" in the boot +target that don't actually do anything but are merely used as anchors in +service dependencies, i.e. they indicate that some sort of milestone in the +boot sequence has been reached. Everything that is part of that milestone +specifies that it should be run *before* that pseudo service and everything +that requires that this milestone has been reached, specifies that it wants +to run afterwards. + +The pseudo targets are (in the order that they are executed): + + * vfs + + All services that do mount point setup go before this, all service that + depend on the fully mounted rootfs go after this. + + * sysinit + + The system has reached a sane state, i.e. the hostname is set, the system + clock has a sane value, modules and kernel parameters are loaded, some + very basic, fundamental services are running. + Everything that is part of that setup process goes between `vfs` and + `sysinit`, everything that requires a sane setup goes *after* `sysinit`. + + * network + + Network configuration is done. All services that do network configuration + should position themselves between `sysinit` and `network`. Everything that + requires a fully configured networking setup should go *after* `network`. + +## Default Bootup Services + +This section outlines the services for the boot target that are enabled by +default. + + +The following services are enabled by default and run *before* the `vfs` target +for filesystem setup: + + * procfs - mount `procfs` to `/proc` and try to mount additional pseudo + filesystems in `/proc` such as `binfmt_misc` + * tmpfs - mount a `tmpfs` to `/tmp` + * sysfs - mount `sysfs` to `/sys` and try to mount additional pseudo + filesystems in `/sys` (e.g. `securityfs`, `configfs`, ...) + * devfs - mount `devtmpfs` to `/dev`, try to mount additional pseudo + filesystems in `/dev` (e.g. `devpts`, `mqueue`, ...) and try to create + some additional device nodes and symlinks. + * tmpfsvar - mount a `tmpfs` to `/var` and populate it with a default set + of files and directories. Overlay mount `/var/lib` with lower dir on + `/cfg/preserve/var_lib/` and upper on `/cfg/overlay/var_lib/`. + * tmpfsrun - mount a `tmpfs` to `/run`, symlink `/var/run` to `/run` and + `/var/lock` to `/run/lock`. + * mountusr - overlay mount setup for `/usr`. Lower dir is on + `/cfg/preserve/usr/` and upper on `/cfg/overlay/usr/`. + + +The following services are enabled by default and configured to run *after* +the `vfs` target and *before* the `sysinit` target: + + * hostname - reload hostname `/etc/hostname` + * loopback - bring the loopback device up + * modules - iterate over the file `/etc/modules` and try to load each module + using modprobe. + * sysctl - restore kernel parameters using `sysctl --system`. See `sysctl(8)` + for a list of possible locations that the parameters are read from. + * usyslogd - Starts and supervises the `usyslogd` syslog implementation. + * klogd - Starts and supervises the `klogd` daemon. + + +The following services are enabled by default and configured to run *after* +the `sysinit` target and *before* the `network` target: + + * ifcfg - static network configuration + Does the static network configuration outlined in [network.md](network.md) + + +The following services are enabled by default and configured to run *after* +the `network` target: + + * gcrond + + +## Default Shutdown and Reboot Services + +For the shutdown and reboot targets, the following services are executed: + + * sigterm - send the SIGTERM signal to all processes and wait for 5 seconds + * sigkill - send the SIGKILL signal to all remaining processes + * ifdown - bring all network interfaces down + * sync - run the sync command + + +## Additional Services not Enabled by Default + + * agetty - A parameterizeable, respawn type `agetty` service. The first + parameter is the terminal device that the getty should run on. + * consolefont - If enabled, run once before sysinit. Sets the console font + to the first parameter. + * dhcpcdmaster - If one or more network interfaces should be configured using + dhcpcd, this service starts a central `dhcpcd` master instance. + * dhcpcd - A parameterizeable single shot service that signals the `dhcpcd` + master that it should configure a specific interface. The first parameter + is the interface that should be configured by `dhcpcd`. + * dnsmasq - A respawn type service for the `dnsmasq` DNS and DHCP server. + * hostapd - If the system should operate a WIFI access point, this respawn + type service can be enabled to manage an instace of the `hostapd` program. + * unbound - A respawn type service that manages an instance of the `unbound` + name resolver. + * hwclock - If the system has a hardware clock, this service can restore the + kernels clock from the hardware at bootup, between the `vfs` and `sysinit` + targets. + * nft - If enabled, restores net filter table rules during boot. + * swclock - For systems that don't have a hardware clock, this service + restores a somewhat usable time from a file during boot. + * swclocksave - For systems that don't have a hardware clock, this service + saves the current time to a file during shutdown or reboot. + * sshd_keygen - A wait type service that generates host keys for the OpenSSH + server and then disables itself. + * sshd - Starts an OpenSSH server after the network pseudo service and after + the sshd_keygen service. + * nginx - Starts the Nginx server after the network pseudo serivce. -- cgit v1.2.3