diff --git a/addon/lib/rmupdate.tcl b/addon/lib/rmupdate.tcl
index 78f72db..c94c928 100644
--- a/addon/lib/rmupdate.tcl
+++ b/addon/lib/rmupdate.tcl
@@ -24,6 +24,9 @@ namespace eval rmupdate {
 	variable mnt_new "/usr/local/addons/rmupdate/var/mnt_new"
 	variable sys_dev "/dev/mmcblk0"
 	variable loop_dev "/dev/loop7"
+	variable install_log "/usr/local/addons/rmupdate/var/install.log"
+	variable install_lock "/usr/local/addons/rmupdate/var/install.lock"
+	variable log_file ""
 }
 
 proc ::rmupdate::compare_versions {a b} {
@@ -31,10 +34,21 @@ proc ::rmupdate::compare_versions {a b} {
 }
 
 proc ::rmupdate::write_log {str} {
+	variable log_file
 	puts stderr $str
-	#set fd [open "/tmp/rmupdate.log" "a"]
-	#puts $fd $str
-	#close $fd
+	if {$log_file != ""} {
+		set fd [open $log_file "a"]
+		puts $fd $str
+		close $fd
+	}
+}
+
+proc ::rmupdate::read_install_log {} {
+	variable install_log
+	set fp [open $install_log r]
+	set data [read $fp]
+	close $fp
+	return $data
 }
 
 proc ::rmupdate::version {} {
@@ -46,7 +60,7 @@ proc ::rmupdate::version {} {
 }
 
 proc ::rmupdate::get_partion_start_and_size {device partition} {
-	set data [exec parted $device unit B print]
+	set data [exec /usr/sbin/parted $device unit B print]
 	foreach d [split $data "\n"] {
 		regexp {^\s*(\d)\s+(\d+)B\s+(\d+)B\s+(\d+)B.*} $d match num start end size
 		if { [info exists num] && $num == $partition } {
@@ -62,13 +76,14 @@ proc ::rmupdate::mount_image_partition {image partition mountpoint} {
 	
 	write_log "Mounting parition ${partition} of image ${image}."
 
-	set p [get_partion_start_and_size $sys_dev $partition]
+	set p [get_partion_start_and_size $image $partition]
+	#write_log "Partiton start=[lindex $p 0], size=[lindex $p 1]."
 	
 	file mkdir $mountpoint
-	catch {exec umount "${mountpoint}"}
-	catch {exec losetup -d $loop_dev}
-	exec losetup -o [lindex $p 0] $loop_dev "${image}"
-	exec mount $loop_dev -o ro "${mountpoint}"
+	catch {exec /bin/umount "${mountpoint}"}
+	catch {exec /sbin/losetup -d $loop_dev}
+	exec /sbin/losetup -o [lindex $p 0] $loop_dev "${image}"
+	exec /bin/mount $loop_dev -o ro "${mountpoint}"
 }
 
 proc ::rmupdate::mount_system_partition {partition_or_filesystem mountpoint} {
@@ -83,13 +98,13 @@ proc ::rmupdate::mount_system_partition {partition_or_filesystem mountpoint} {
 	write_log "Remounting filesystem ${partition_or_filesystem} (rw)."
 	
 	file mkdir $mountpoint
-	catch {exec umount "${mountpoint}"}
-	exec mount -o bind $partition_or_filesystem "${mountpoint}"
-	exec mount -o remount,rw "${mountpoint}"
+	catch {exec /bin/umount "${mountpoint}"}
+	exec /bin/mount -o bind $partition_or_filesystem "${mountpoint}"
+	exec /bin/mount -o remount,rw "${mountpoint}"
 }
 
 proc ::rmupdate::umount {device_or_mountpoint} {
-	exec umount "${device_or_mountpoint}"
+	exec /bin/umount "${device_or_mountpoint}"
 }
 
 proc ::rmupdate::get_filesystem_size_and_usage {device_or_mountpoint} {
@@ -128,11 +143,11 @@ proc ::rmupdate::check_sizes {image} {
 		umount $mnt_new
 		umount $mnt_cur
 		
-		# Minimum free space 100 MB
-		if { [expr {$new_used+100*1024*1024}] >= $cur_size } {
+		if { [expr {$new_used*1.5}] > $cur_size && [expr {$new_used+50*1024*1024}] >= $cur_size } {
 			error "Current filesystem of partition $partition (${cur_size} bytes) not big enough (new usage: ${new_used} bytes)."
 		}
 	}
+	write_log "Sizes of filesystems checked successfully."
 }
 
 proc ::rmupdate::update_filesystems {image} {
@@ -150,8 +165,9 @@ proc ::rmupdate::update_filesystems {image} {
 		mount_image_partition $image $partition $mnt_new
 		mount_system_partition $partition $mnt_cur
 		
-		write_log "Rsyncing filesystem."
+		write_log "Rsyncing filesystem of partition ${partition}."
 		set data [exec rsync --progress --archive --delete "${mnt_new}/" "${mnt_cur}"]
+		write_log "Rsync finished."
 		
 		umount $mnt_new
 		umount $mnt_cur
@@ -204,6 +220,7 @@ proc ::rmupdate::get_latest_firmware_version {} {
 
 proc ::rmupdate::download_firmware {version} {
 	variable img_dir
+	variable log_file
 	set image_file "${img_dir}/RaspberryMatic-${version}.img"
 	set download_url ""
 	foreach e [get_available_firmware_downloads] {
@@ -220,7 +237,13 @@ proc ::rmupdate::download_firmware {version} {
 	regexp {/([^/]+)$} $download_url match archive_file
 	set archive_file "${img_dir}/${archive_file}"
 	file mkdir $img_dir
-	exec wget "${download_url}" --no-check-certificate -q --output-document=$archive_file
+	if {$log_file != ""} {
+		exec wget "${download_url}" --show-progress --progress=dot:giga --no-check-certificate --quiet --output-document=$archive_file 2>>${log_file}
+		write_log ""
+	} else {
+		exec wget "${download_url}" --no-check-certificate --quiet --output-document=$archive_file
+	}
+	write_log "Download completed."
 	
 	write_log "Extracting firmware ${archive_file}."
 	set data [exec unzip -ql "${archive_file}"]
@@ -295,18 +318,57 @@ proc ::rmupdate::get_firmware_info {} {
 	return $json
 }
 
-proc ::rmupdate::install_firmware_version {version} {
-	set firmware_image ""
-	#foreach e [get_available_firmware_images] {
-	#	set v [get_version_from_filename $e]
-	#	if {$v == $version} {
-	#		set firmware_image $e
-	#		break
-	#	}
-	#}
-	if {$firmware_image == ""} {
-		download_firmware $version
+proc ::rmupdate::install_process_running {} {
+	variable install_lock
+	
+	if {! [file exists $install_lock]} {
+		return 0
 	}
+	
+	set fp [open $install_lock "r"]
+	set lpid [string trim [read $fp]]
+	close $fp
+	
+	if {[file exists "/proc/${lpid}"]} {
+		return 1
+	}
+	
+	file delete $install_lock
+	return 0
+}
+
+proc ::rmupdate::install_firmware_version {version} {
+	if {[rmupdate::install_process_running]} {
+		error "Another install process is running."
+	}
+	
+	variable install_lock
+	variable log_file
+	variable install_log
+	
+	set fd [open $install_lock "w"]
+	puts $fd [pid]
+	close $fd
+	
+	file delete $install_log
+	set log_file $install_log
+	set firmware_image ""
+	
+	foreach e [get_available_firmware_images] {
+		set v [get_version_from_filename $e]
+		if {$v == $version} {
+			set firmware_image $e
+			break
+		}
+	}
+	if {$firmware_image == ""} {
+		set firmware_image [download_firmware $version]
+	}
+	
+	check_sizes $firmware_image
+	update_filesystems $firmware_image
+	
+	file delete $install_lock
 }
 
 #puts [rmupdate::get_latest_firmware_version]
diff --git a/addon/rmupdate.tcl b/addon/rmupdate.tcl
index 3c300f6..ccc54ca 100644
--- a/addon/rmupdate.tcl
+++ b/addon/rmupdate.tcl
@@ -39,11 +39,11 @@ proc main {} {
 	
 	if {$cmd == "show_current"} {
 		puts [rmupdate::get_current_firmware_version]
-	} elsif {$cmd == "show_latest"} {
+	} elseif {$cmd == "show_latest"} {
 		puts [rmupdate::get_latest_firmware_version]
-	} elsif {$cmd == "install_latest"} {
+	} elseif {$cmd == "install_latest"} {
 		rmupdate::install_firmware_version [rmupdate::get_latest_firmware_version]
-	} elsif {$cmd == "install"} {
+	} elseif {$cmd == "install"} {
 		if {$argc < 2} {
 			usage
 			exit 1
diff --git a/addon/www/index.html b/addon/www/index.html
index 5666b75..2094f82 100644
--- a/addon/www/index.html
+++ b/addon/www/index.html
@@ -31,13 +31,14 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 	<title>RaspberryMatic Update Addon</title>
 	<script>
 		var message_timer_id = null;
+		var install_running = false;
 		
 		function display_message(type, html, millis) {
 			clear_message();
 			$('#message').html(html);
 			$('#message').attr('class', 'ui ' + type + ' message visible');
-			$('#message-edit-bridge').html(html);
-			$('#message-edit-bridge').attr('class', 'ui ' + type + ' message visible');
+			$('#message-log').html(html);
+			$('#message-log').attr('class', 'ui ' + type + ' message visible');
 			message_timer_id = setTimeout(clear_message, millis);
 		}
 		
@@ -48,25 +49,27 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 			message_timer_id = null;
 			$('#message').html('');
 			$('#message').attr('class', 'ui message hidden');
-			$('#message-edit-bridge').html('');
-			$('#message-edit-bridge').attr('class', 'ui message hidden');
+			$('#message-log').html('');
+			$('#message-log').attr('class', 'ui message hidden');
+		}
+		
+		function default_error_callback(xhr, ajaxOptions, thrownError) {
+			console.error(xhr);
+			err = thrownError;
+			try {
+				obj = JSON.parse(xhr.responseText);
+				if (obj.error != null) {
+					err = obj.error;
+				}
+			}
+			catch(e) {
+			}
+			display_message('error', 'An error occurred: ' + err, 6000000);
 		}
 		
 		function rest(method, path, data, success_callback, error_callback) {
 			if (!error_callback) {
-				error_callback = function(xhr, ajaxOptions, thrownError) {
-					console.error(xhr);
-					err = thrownError;
-					try {
-						obj = JSON.parse(xhr.responseText);
-						if (obj.error != null) {
-							err = obj.error;
-						}
-					}
-					catch(e) {
-					}
-					display_message('error', 'An error occurred: ' + err, 60000);
-				}
+				error_callback = default_error_callback
 			}
 			$.ajax({
 				url: "rest.cgi?" + path,
@@ -78,49 +81,35 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 			});
 		}
 		
-		function install_firmware(version) {
-			$('#modal-log').modal('show');
-			//$('#log-content').append('Some text<br/>');
-			//$('#modal-log').modal('refresh');
-			//$('#modal-log').modal('hide');
-			var xhr = new XMLHttpRequest();
-			xhr.open('GET', 'rest.cgi?/install_firmware', true);
-			xhr.send(null);
-			var timer;
-			timer = window.setInterval(function() {
-				if (xhr.readyState == XMLHttpRequest.DONE) {
-					window.clearTimeout(timer);
-					//$('body').append('done <br />');
+		function update_install_log() {
+			rest("GET", "/read_install_log", null, function(data) {
+				$('#log-content').html(data.replace(/\n/g, '<br />'));
+				$('#modal-log').modal('refresh');
+				$('#log-content').scrollTop($('#log-content').prop("scrollHeight"));
+				if (install_running) {
+					setTimeout(update_install_log, 1000);
 				}
-				//$('body').append('state: ' + xhr.readyState + '<br />');
-				console.log(xhr.responseText);
-				$('#log-content').append(xhr.responseText + '<br/>');
-				//$('body').append('data: ' + xhr.responseText + '<br />');
-			}, 1000);
-			/*
-			var last_response_len = false;
-			$.ajax('rest.cgi?/install_firmware', {
-				xhrFields: {
-					onprogress: function(e) {
-						var this_response, response = e.currentTarget.response;
-						if(last_response_len === false) {
-							this_response = response;
-							last_response_len = response.length;
-						}
-						else {
-							this_response = response.substring(last_response_len);
-							last_response_len = response.length;
-						}
-						console.log(this_response);
-					}
-				}
-			}).done(function(data) {
-				console.log('Complete response = ' + data);
-			}).fail(function(data) {
-				console.log('Error: ', data);
 			});
-			console.log('Request Sent');
-			*/
+		}
+		
+		function install_firmware(version) {
+			display_message('info', 'Installing firmware ' + version + '.', 6000000);
+			install_running = true;
+			clear_message();
+			$('#log-content').html('');
+			$('#modal-log').modal('show');
+			rest("POST", "/start_install_firmware", version,
+				function(data) {
+					install_running = false;
+					display_message('success', 'Firmware ' + version + ' successfully installed.', 6000000);
+				},
+				function(xhr, ajaxOptions, thrownError) {
+					install_running = false;
+					//$('#modal-log').modal('hide');
+					default_error_callback(xhr, ajaxOptions, thrownError);
+				}
+			);
+			setTimeout(update_install_log, 1000);
 		}
 		
 		$(document).ready(function() {
@@ -174,13 +163,16 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 		</table>
 	</div>
 	
-	<div id="modal-log" class="ui modal">
+	<div style="height:80%" id="modal-log" class="ui modal">
 		<i class="close icon"></i>
 		<div class="header">
 			Progress
 		</div>
-		<div id="log-content" class="content">
-		Line 1
+		<div class="content">
+			<div id="message-log" class="ui message hidden">
+			</div>
+			<pre style="max-height:80%; overflow-x:hidden; overflow-y:auto; white-space: pre-wrap;" id="log-content" class="content">
+			</pre>
 		</div>
 	</div>
 </body>
diff --git a/addon/www/rest.cgi b/addon/www/rest.cgi
index d4a24d2..9dcbcfa 100644
--- a/addon/www/rest.cgi
+++ b/addon/www/rest.cgi
@@ -47,43 +47,36 @@ proc process {} {
 			return "\"[rmupdate::version]\""
 		} elseif {[lindex $path 1] == "get_firmware_info"} {
 			return [rmupdate::get_firmware_info]
-		} elseif {[lindex $path 1] == "install_firmware"} {
-			fconfigure stdout -buffering none
-			#puts "Content-Type: application/octet-stream"
-			puts "Content-Type: text/html; charset=utf-8"
-			puts "Status: 200 OK";
-			puts ""
-			flush stdout
-			after 1000
-			puts "Line 1\n"
-			flush stdout
-			after 1000
-			puts "Line 2\n"
-			flush stdout
-			after 1000
-			puts "Line 3\n"
-			flush stdout
-			after 1000
-			puts "Line 4\n"
-			flush stdout
-			return ""
+		} elseif {[lindex $path 1] == "start_install_firmware"} {
+			regexp {^([\d\.]+)$} $data match version
+			if { [info exists version] && $version != "" } {
+				rmupdate::install_firmware_version $version
+				return "\"done\""
+			} else {
+				error "Invalid version: ${data}"
+			}
+		} elseif {[lindex $path 1] == "read_install_log"} {
+			variable content_type "text/html"
+			return [rmupdate::read_install_log]
 		}
 	}
 	error "invalid request" "Not found" 404
 }
 
+variable content_type "application/json"
+
 if [catch {process} result] {
 	set status 500
 	if { [info exists $errorCode] } {
 		set status $errorCode
 	}
-	puts "Content-Type: application/json"
+	puts "Content-Type: ${content_type}"
 	puts "Status: $status";
 	puts ""
 	set result [json_string $result]
 	puts -nonewline "\{\"error\":\"${result}\"\}"
-} elseif {$result != ""} {
-	puts "Content-Type: application/json"
+} else {
+	puts "Content-Type: ${content_type}"
 	puts "Status: 200 OK";
 	puts ""
 	puts -nonewline $result