vpsFree k3s install script (ubuntu 22.04)

vpsfree-k3s-install.sh

#!/bin/sh

K3S_SERVICE_NAME="k3s.service"
K3S_FAKE_SERVICE_NAME="k3s-fake.service"

# helper functions for output messages
info()
{
    echo '[INFO] ' "$@"
}
warn()
{
    echo '[WARN] ' "$@" >&2
}
fatal()
{
    echo '[ERROR] ' "$@" >&2
    exit 1
}

# check installation is not processed yet
check_status() {
    ensure_unit_not_exists $K3S_SERVICE_NAME
    ensure_unit_not_exists $K3S_FAKE_SERVICE_NAME

    # check curl presence
    if ! type "curl" > /dev/null; then
        fatal "curl command is missing."
    fi
}

# install k3s, do not start
k3s_install() {
    info 'Installing k3s...'
    curl -sfL https://get.k3s.io | INSTALL_K3S_SKIP_START=true sh -
}

# apply system prerequisities
k3s_fakes_create() {
    info 'Applying system fakes...'

    ln -s /bin/true /usr/local/sbin/modprobe
    
    mkdir -p /opt/k3s/fake
    cat > /opt/k3s/fake.sh <<EOF
#!/bin/bash 
cd /opt/k3s/fake
echo 0 > panic
mount --bind panic /proc/sys/kernel/panic
echo 0 > panic_on_oops
mount --bind panic_on_oops /proc/sys/kernel/panic_on_oops
echo 0 > overcommit_memory
mount --bind overcommit_memory /proc/sys/vm/overcommit_memory
mkdir block
mount -o bind block/ /sys/block/
EOF
    chmod +x /opt/k3s/fake.sh
    cat > /etc/systemd/system/k3s-fake.service <<EOF
[Unit]
Before=k3s.service

[Service]
ExecStart=/opt/k3s/fake.sh

[Install]
WantedBy=default.target
EOF

    chmod 644 /etc/systemd/system/k3s-fake.service

    info 'Faked.'
}

# updates k3s service to use fakes
k3s_modify() {
    cp /etc/systemd/system/k3s.service /etc/systemd/system/k3s.service.orig
    sed -i 's/ExecStartPre=.*br_netfilter.*/ExecStartPre=-\/usr\/local\/sbin\/modprobe br_netfilter/g' /etc/systemd/system/k3s.service
    sed -i 's/ExecStartPre=.*overlay.*/ExecStartPre=-\/usr\/local\/sbin\/modprobe overlay/g' /etc/systemd/system/k3s.service
}

# enables and starts services
enable_and_start() {
    systemctl daemon-reload
    systemctl enable k3s-fake.service
    systemctl start k3s-fake.service
    systemctl start k3s.service
}

# checks if unit exists, usage: unit_exists "k3s.service"
unit_exists() {
    [ $(systemctl list-unit-files "${1}" | wc -l) -gt 3 ]
}

# exit script if unit exists, usage: ensure_unit_not_exists "k3s.service"
ensure_unit_not_exists() {
    if unit_exists "$1" ; then
        fatal "Unit $1 already exist."
    fi
}

# process installation
{
    check_status
    k3s_install
    k3s_fakes_create
    k3s_modify
    enable_and_start
}