Use ncat instead of nc.traditional in VM scripts

.github/workflows/vm.yml

@@ -100,13 +100,13 @@ jobs:
           sudo apt update
           case ${{ matrix.arch }} in
             aarch64)
-              sudo apt install -y --no-install-recommends netcat-traditional qemu-system-aarch64 qemu-efi-aarch64 ipxe-qemu
+              sudo apt install -y --no-install-recommends ncat qemu-system-aarch64 qemu-efi-aarch64 ipxe-qemu
               ;;
             x86 | amd64)
-              sudo apt install -y --no-install-recommends netcat-traditional qemu-system-x86
+              sudo apt install -y --no-install-recommends ncat qemu-system-x86
               ;;
             armv6)
-              sudo apt install -y --no-install-recommends netcat-traditional qemu-system-arm
+              sudo apt install -y --no-install-recommends ncat qemu-system-arm
               ;;
             *)
               echo "Don't know what to install"
@@ -138,7 +138,7 @@ jobs:
           if [ "${{ matrix.os }}-${{ matrix.arch }}" == "raspios-armv6" ]; then
             # qemu doesn't really support armv6 shutting down (if that's a thing anyway???)
             # Instead linux kernel panics because init is exiting. Let's wait for that.
-            vm/wait_for_string.sh 'not syncing: Attempted to kill init' nc.traditional localhost 2222
+            vm/wait_for_string.sh 'not syncing: Attempted to kill init' ncat --no-shutdown localhost 2222
             kill -INT $(cat vm/${{ matrix.os }}-${{ matrix.arch }}/pid.txt)
           else
             echo "Waiting for VM to shut down..."

vm/README.md

@@ -60,18 +60,20 @@ Here are some guidelines for working on the scripts:
 - Use `set -e -o pipefail`. If this gets in your way, use `|| true` only in the
   places that need it. This way failures are not silenced except where you
   expect to get failures.
-- Use `nc.traditional` instead of `nc`. There are several different versions of
-  netcat, and they are similar but incompatible in subtle ways. For example,
-  `echo | nc ...` doesn't work as expected with `ncat`, because `ncat` closes
-  the connection when it gets EOF on stdin.
+- Use `ncat` instead of `nc`. The `nc` command can be any of several different
+  netcat implementations: it may be same as `ncat`, or something else. The
+  different implementations are similar but incompatible in subtle ways. For
+  example, when `nc` gets EOF on stdin, some `nc` implementations (like `ncat`)
+  close the connection while others keep it open. I chose to use `ncat` because
+  it is available with the same name in most linux distros.
 - Use the [`wait_for_string.sh`](./wait_for_string.sh) script instead of the
   `expect` program, for two reasons:
     - Jou developers already need to know at least 4 programming languages, and
       I don't really want to add Tcl to the mix.
     - `expect` would be an unnecessary dependency.
 
 Dependencies (in addition to what you need for Jou anyway):
-- All architectures and operating systems: `sudo apt install wget openssh-client netcat-traditional`
+- All architectures and operating systems: `sudo apt install wget openssh-client ncat`
 - x86: `sudo apt install qemu-system-x86`
 - aarch64: `sudo apt install qemu-system-aarch64 qemu-efi-aarch64 ipxe-qemu`
 - armv6: `sudo apt install qemu-system-arm`

vm/alpine.sh

@@ -65,13 +65,13 @@ if ! [ -f disk.img ]; then
     qemu_pid=$!
 
     echo "Waiting for temporary VM to boot so we can install alpine..."
-    until echo | ../wait_for_string.sh 'localhost login:' nc.traditional localhost 4444; do
+    until echo | ../wait_for_string.sh 'localhost login:' ncat --no-shutdown localhost 4444; do
         sleep 1
         kill -0 $qemu_pid  # Stop if qemu dies
     done
 
     echo "Logging in to temporary VM..."
-    echo root | ../wait_for_string.sh 'localhost:~#' nc.traditional localhost 4444
+    echo root | ../wait_for_string.sh 'localhost:~#' ncat --no-shutdown localhost 4444
 
     echo "Installing alpine..."
     echo "
@@ -82,7 +82,7 @@ setup-alpine -f answerfile -e
 y
 sync
 poweroff
-" | nc.traditional localhost 4444
+" | ncat --no-shutdown localhost 4444
     wait  # Make sure qemu has died before we proceed further
     trap - EXIT  # Don't delete disk.img when we exit
 fi

vm/netbsd.sh

@@ -92,7 +92,7 @@ if ! timeout 5 ../ssh.sh echo hello; then
     # We consider the VM started when it shows login prompt on serial port.
     # At that point it has also started ssh.
     echo "Waiting for VM to boot..."
-    until echo | ../wait_for_string.sh 'login:' nc.traditional localhost 4444; do
+    until echo | ../wait_for_string.sh 'login:' ncat --no-shutdown localhost 4444; do
         sleep 1
         kill -0 $qemu_pid  # Stop if qemu dies
     done
@@ -105,7 +105,7 @@ mkdir .ssh
 chmod 700 .ssh
 echo '$(../keygen.sh)' > .ssh/authorized_keys
 echo ALL'DONE'NOW
-exit" | ../wait_for_string.sh 'ALLDONENOW' nc.traditional localhost 4444
+exit" | ../wait_for_string.sh 'ALLDONENOW' ncat --no-shutdown localhost 4444
         echo "Now ssh setup is done, let's check one last time..."
         ../ssh.sh echo hello  # Check that it works
     fi

vm/raspios.sh

@@ -181,7 +181,7 @@ else
     disown
 
     echo "Waiting for VM to boot..."
-    until echo | ../wait_for_string.sh 'raspberrypi login:' nc.traditional localhost 4444; do
+    until echo | ../wait_for_string.sh 'raspberrypi login:' ncat --no-shutdown localhost 4444; do
         sleep 1
         kill -0 $qemu_pid  # Stop if qemu dies
     done

vm/wait_for_string.sh

@@ -9,7 +9,7 @@
 # For example, this logs in as root to serial console on localhost:4444, and
 # waits until the shell prompt appears:
 #
-#   $ echo root | ./wait_for_string.sh "root@localhost:~#" nc.traditional localhost 4444
+#   $ echo root | ./wait_for_string.sh "root@localhost:~#" ncat --no-shutdown localhost 4444
 #
 # Here is another example, which is more useful for developing this script. It
 # tells Python to print "blah" and "foobar", with 1 second delays before and