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|
#! /usr/bin/env bash
# Generate systemd .service file for QEMU/KVM virtual machines.
#
# Normally the machines are run from a dedicated user account with its home
# directory containing all the relevant files (management scripts, images,
# configurations, and sockets). However, this can be overriden with the
# following options
#
# --home <dir>
# The virtual machines "home" directory. If unspecified, the user's home
# directory is assumed.
#
# --bin <dir>
# The virtual machines management scripts directory. If unspecified,
# <home>/bin is assumed. If specified as relative, then assumed relative
# to <home>.
#
# --etc <dir>
# The virtual machines configuration files directory. If unspecified,
# <home>/etc is assumed. If specified as relative, then assumed relative
# to <home>.
#
# --var <dir>
# The virtual machines image files directory. If unspecified, <home>/var is
# assumed. If specified as relative, then assumed relative to <home>.
#
# --run <dir>
# The virtual machines sockets directory. If unspecified, <home>/run is
# assumed. If specified as relative, then assumed relative to <home>.
#
# If <user> is unspecified, the current user is assumed. If <group> is
# unspecified, the user's primary group is assumed.
#
usage="usage: $0 [<options>] [<user>] [<group>]"
owd="$(pwd)"
trap "{ cd '$owd'; exit 1; }" ERR
set -o errtrace # Trap in functions.
function info () { echo "$*" 1>&2; }
function error () { info "$*"; exit 1; }
home=
bin=
etc=
var=
run=
while [ "$#" -gt 0 ]; do
case "$1" in
--home)
shift
home="$1"
shift
;;
--bin)
shift
bin="$1"
shift
;;
--etc)
shift
etc="$1"
shift
;;
--var)
shift
var="$1"
shift
;;
--run)
shift
run="$1"
shift
;;
*)
break
;;
esac
done
user="$1"
if [ -z "$user" ]; then
user="$(id -un)"
fi
group="$2"
if [ -z "$group" ]; then
group="$(id -un "$user")"
fi
if [ -z "$home" ]; then
home="$(eval echo ~$user)"
fi
function complete_dir () # <default> <home> <dir>
{
local r
if [ -z "$3" ]; then
r="$2/$1"
elif [ "${3:0:1}" != "/" ]; then
r="$2/$3"
else
r="$3"
fi
echo "$(realpath --no-symlinks --canonicalize-missing "$r")"
}
bin="$(complete_dir bin "$home" "$bin")"
etc="$(complete_dir etc "$home" "$etc")"
var="$(complete_dir var "$home" "$var")"
run="$(complete_dir run "$home" "$run")"
name="vm-$user"
file="$name@.service"
# Thinks that must be \-escaped:
#
# - $ (including in comments)
# - \ (e.g., in line continuations)
#
cat <<EOF >"$file"
# $file -- QEMU/KVM machine service template for systemd
#
# user: $user
# group: $group
# bin: $bin
# etc: $etc
# var: $var
# run: $run
#
# To install:
#
# sudo cp $file /etc/systemd/system/
# sudo chmod 644 /etc/systemd/system/$file
#
# cp ... $var/<machine>.img
# nano $etc/<machine>.conf # Specify RAM, CPU, TAP, MAC, etc.
#
# sudo systemctl start $name@<machine>
# sudo systemctl status $name@<machine>
# login-machine $run/<machine>-con.sock
# sudo systemctl stop $name@<machine>
#
# sudo systemctl enable $name@<machine>
[Unit]
Description=QEMU/KVM virtual machine %I
Wants=network-online.target
#After=network-online.target
After=multi-user.target
[Service]
User=$user
Group=$user
UMask=0007
WorkingDirectory=~
Environment=CPU=1
Environment=RAM=2G
# These MUST be specific in EnvironmentFile!
#
#Environment=TAP=
#Environment=MAC=
# Note that using variable expansion in EnvironmentFile does not work (at
# least not with systemd 229).
#
EnvironmentFile=$etc/%i.conf
# Note that the first word of ExecStart cannot contain variable expansions.
#
ExecStart=$bin/vm-start \\
--cpu \${CPU} \\
--ram \${RAM} \\
--tap \${TAP} \\
--mac \${MAC} \\
--pid $run/%i.pid \\
--monitor $run/%i-mon.sock \\
--console $run/%i-con.sock \\
$var/%i.img
ExecStop=$bin/vm-stop $run/%i.pid $run/%i-mon.sock
# This makes sure systemd waits for the ExecStart command to exit rather
# than killing it as soon as ExecStop exits (this is necessary since our
# vm-stop may exit just before vm-start).
#
KillMode=none
TimeoutStopSec=60
[Install]
WantedBy=multi-user.target
EOF
info "generated $file for"
info " user: $user"
info " group: $group"
info " bin: $bin"
info " etc: $etc"
info " var: $var"
info " run: $run"
|
