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Filename : rtc-sys-time-init-generator
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#!/bin/sh

# This generator instantiates rtc-sys-time-init@dev-rtc*.service by hooking it
# into sysinit.target when requested by kernel command line parameter
# ubuntu_core.rtc_sys_time_init=dev-rtc*. Instances are based on the template
# rtc-sys-time-init@.service that is not generated.

DEBUG_ENABLE="false"

log() {
    echo "$@" >> "/dev/kmsg"
}

debug() {
    if [ "$DEBUG_ENABLE" = "true" ]; then
        log "$@"
    fi
}

normal_dir="$1"

# Look for kernel command line parameter ubuntu_core.rtc_sys_time_init
if ! dev_node=$(/usr/libexec/core/get-arg "ubuntu_core.rtc_sys_time_init"); then
    debug "Kernel command line does not contain parameter ubuntu_core.rtc_sys_time_init"
    exit 0
fi

# Expect /dev/rtc and /dev/rtc0 to /dev/rtc9
if ! expr "$dev_node" : '^/dev/rtc[0-9]\{0,1\}$' >/dev/null; then
    log "Warning: kernel command line parameter ubuntu_core.rtc_sys_time_init=$dev_node seems invalid"
    # Do not exit, require highly visible service failure
fi

dev_unit=$(systemd-escape --path "$dev_node")
instance="rtc-sys-time-init@$dev_unit.service"
target_dir="$normal_dir/sysinit.target.wants"
target_link=$target_dir/$instance
template="/usr/lib/systemd/system/rtc-sys-time-init@.service"

if [ -L "$target_link" ]; then
    debug "Already enabled"
    exit 0
fi

if [ -d "$target_dir" ] || mkdir -p "$target_dir"; then
    if ln -snf "$template" "$target_link"; then
        debug "Enabled $instance: $target_link -> $template"
    else
        log "Error: cannot create symlink $target_link -> $template"
        exit 1
    fi
else
    log "Error: cannot create target directory $target_dir"
fi