Merge pull request #283406 from tfc/nixos-rebuild-socket

nixos-rebuild: Handle too-long tmpdir paths on macOS

nixos/tests/nixos-rebuild-target-host.nix

@@ -132,5 +132,10 @@ import ./make-test-python.nix ({ pkgs, ... }: {
         deployer.succeed("passh -c 3 -C -p ${nodes.target.users.users.bob.password} -P \"\[sudo\] password\" nixos-rebuild switch -I nixos-config=/root/configuration-3.nix --target-host bob@target --use-remote-sudo &>/dev/console")
         target_hostname = deployer.succeed("ssh alice@target cat /etc/hostname").rstrip()
         assert target_hostname == "config-3-deployed", f"{target_hostname=}"
+
+      with subtest("Deploy works with very long TMPDIR"):
+        tmp_dir = "/var/folder/veryveryveryveryverylongpathnamethatdoesnotworkwithcontrolpath"
+        deployer.succeed(f"mkdir -p {tmp_dir}")
+        deployer.succeed(f"TMPDIR={tmp_dir} nixos-rebuild switch -I nixos-config=/root/configuration-1.nix --target-host root@target &>/dev/console")
     '';
 })

pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh

@@ -407,6 +407,13 @@ fi
 
 tmpDir=$(mktemp -t -d nixos-rebuild.XXXXXX)
 
+if [[ ${#tmpDir} -ge 60 ]]; then
+    # Very long tmp dirs lead to "too long for Unix domain socket"
+    # SSH ControlPath errors. Especially macOS sets long TMPDIR paths.
+    rmdir "$tmpDir"
+    tmpDir=$(TMPDIR= mktemp -t -d nixos-rebuild.XXXXXX)
+fi
+
 cleanup() {
     for ctrl in "$tmpDir"/ssh-*; do
         ssh -o ControlPath="$ctrl" -O exit dummyhost 2>/dev/null || true