update ssh keygen section

infrastructure-guide/home.md

@@ -59,6 +59,11 @@ Access to the redhat.com knowledge base:
 
 # SSH Certificates / Signing Public User Keys
 
+Generate a ssh key e.g. as follows:
+```bash
+ssh-keygen -o -a 100 -t ed25519 -f ~/.ssh/linux_id_ed25519
+```
+
 Use the [user ca certificate](https://git.psi.ch/linux-infra/core-linux-secrets/-/blob/main/ssh-ca/user-ca.gpg), but this is automated by pasting below function into your shell
 ```bash
 function sign-user-ssh-key {
@@ -70,7 +75,8 @@ function sign-user-ssh-key {
         # so it never ends up on the file system
 
         umask 077
-        pipe="$(mktemp --dry-run)"
+        pipe_base="$(mktemp)" # MacOS does not know about --dry-run
+        pipe="${pipe_base}.pipe"
         echo "mkfifo '$pipe'"
         mkfifo "$pipe" || return 1
         [ -p "$pipe" ] || return 1
@@ -78,8 +84,8 @@ function sign-user-ssh-key {
         pass ssh-ca/user-ca > "$pipe" &
         echo "ssh-keygen -s '$pipe' -I '$name' -n '$name' -V +55w '$pubkey'"
         ssh-keygen -s "$pipe" -I "$name" -n "$name" -V +55w "$pubkey"
-        echo "rm '$pipe'"
-        rm "$pipe"
+        echo "rm '$pipe' '$pipe_base'"
+        rm "$pipe" "$pipe_base"
     )
 }
 ```