Add more text to contestops readme

.gitignore

@@ -2,4 +2,5 @@
 /osbuild/
 
 /contestops/certs/
+/contestops/backups*
 /contestops/local.known_hosts

contestops/readme.md

@@ -2,8 +2,8 @@
 
 Here are instructions and various scripts and files for running contests.
 
-The setup consists of a machine for each contestant, a machine running the grader, and an admin machine.
+The setup consists of a machine for each contestant, a machine running the grader, and an admin machine (e.g. your personal laptop).
-All these should be connected through a network, preferably wired.
+All these should be connected through a network.
 The grader can be a machine accessible over the internet or in the local network.
 
 ## Grader setup
@@ -17,7 +17,7 @@ sudo apt install ntpsec
 ```
 
 Configure the grader to accept client certificates.
-The CA certificate (`certs/ca.pem`) is generated as part of the admin setup.
+The CA certificate (`certs/ca.pem`) is generated as part of the admin setup below.
 
 ## Contestant machine setup
 
@@ -36,15 +36,30 @@ The OS is loaded into RAM during boot, so you can remove the stick once the boot
 ## Network setup
 
 If there is not already an existing network, you need to set it up yourself.
-Connect all contestant machines and the admin machine to a network switch with LAN cables.
+You can use either WiFi or wired Ethernet.
-If you use multiple switches, don't forget to also link the switches together.
+WiFi has the advantage that you don't need to bring and install all those Ethernet cables, and avoids the ugly cable mess.
 
-If the grader must be accessed over the internet, you can connect the admin machine to WiFi or USB tethering with a phone.
+**Ethernet:**
-You can then share the internet with the local network.
+Connect all contestant machines and the admin machine to a network switch with Ethernet cables.
+If you use multiple switches, don't forget to also link the switches together, such that the entire network forms a tree.
 
-If you have Gnome, go to Network settings, click on the gear on the Ethernet connection, go to IPv4 tab, and select "Shared to other computers".
+**WiFi:**
+The contestant OS already has a WiFi pre-configured.
+The SSID is `contest`, and the password is configured in the `contestant_wifi_password` variable in `os/config/config.toml`.
+Configure the access point with this SSID and password, and the machines will connect automatically.
 
-If you have docker installed, this doesn't work yet, because docker blocks routing.
+For larger contests (10 or more contestants) it's recommended to use a dedicated device as the Internet router.
+SOI has a FRITZ!Box 4040 which can be used for this.
+Here, you can easily get the list of IP addresses of contestant machines from the web interface.
+It's best to connect the admin machine to the router box over LAN instead of WiFi, such that admin traffic only takes one wireless hop instead of two.
+
+For smaller contests, you can also use the admin machine as a router.
+For Ethernet, if you have Gnome, go to Network settings, click on the gear on the Ethernet connection, go to IPv4 tab, and select "Shared to other computers".
+For WiFi, you can set up a WiFi hotspot in the WiFi settings.
+However, with a hotspot enabled, Gnome does not let you connect to a WiFi network for Internet access at the same time, even though the hardware would in many cases support it.
+Instead, you can connect a phone to WiFi and to your laptop with USB and enable USB tethering on the phone.
+
+If you have Docker installed, this doesn't work yet, because docker blocks routing.
 You can fix it by running the following commands.
 
 ```bash
@@ -81,6 +96,8 @@ sudo apt install golang-cfssl
 ./create-certs.sh
 ```
 
+## Before the contest
+
 Edit `local.ssh_config` and create an entry with hostname and IP address for each contestant machine.
 You can get the IP address by running `ip addr` in a terminal on the contestant machine.
 
@@ -118,7 +135,16 @@ Assign users to machines.
 ./assign-user.sh contestant02 binna1
 ```
 
+You may want to test on one machine that the certificate was properly installed and the grader is accessible.
+This should only be done after the machines are configured and users assigned, but with a contest lock start time before the current time.
+You can then set the start time and apply the contest lock config again.
+
+```bash
+parallel-scp -x "-F local.ssh_config" -h hostlist ./contest-lock.json /etc/contest-lock.json
+```
+
 Start periodic backup of contestant machines.
+Backups are stored every 2 minutes in the folder `backups`.
 
 ```bash
 ./backup-create.sh timer
@@ -138,6 +164,19 @@ replacing `contestant03` in the commands below with the spare machine hostname.
 rsync -e "ssh -F local.ssh_config" -av --chown contestant:contestant backups/contestantxx/xxxx/ contestant03:/home/contestant/
 ```
 
+## After the contest
+
+Stop the periodic backup command with Ctrl+C.
+Rename the `backups` folder to e.g. `backups-day1`.
+
+You can shut down all machines.
+
+```
+parallel-ssh -x "-F local.ssh_config" -h hostlist poweroff
+```
+
+Machines should be shut down and booted again from USB stick between contests (e.g. between practice and actual contest) to ensure all data is erased.
+
 ## Contest lock screen
 
 The contest lock screen is a gnome extension which can lock the screen and show a countdown until the contest starts.