[systemd-devel] [PATCH] detect-virt: detect User-Mode Linux

[Ramkumar Ramachandra]

In a User-Mode Linux session:

  $ systemd-detect-virt
  none

Although it is possible to reliably detect virtualization:

  $ cat /proc/cpuinfo
  processor       : 0
  vendor_id       : User Mode Linux
  model name      : UML
  mode            : skas
  host            : Linux kytes 3.11.0-rc1-00009-ge5fd680 (...)
  bogomips        : 7007.43

So, grep for the string "User Mode Linux" in /proc/cpuinfo, and say
"uml" when asked.

Cc: Lennart Poettering <lennart at poettering.net>
Signed-off-by: Ramkumar Ramachandra <artagnon at gmail.com>
---
 It seems that UM does not have a proper tty system; I force
 systemd to use the /dev/console by doing:

 $ mv /etc/systemd/system/getty.target.wants/{getty at tty1.service,getty at console.service}

 The first step towards supporting UM properly is to detect it, right?
 So, here's a small patch.  I tested it briefly.

 src/shared/virt.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/shared/virt.c b/src/shared/virt.c
index 1c86a3d..25b3016 100644
--- a/src/shared/virt.c
+++ b/src/shared/virt.c
@@ -67,6 +67,7 @@ int detect_vm(const char **id) {
         const char *j, *k;
         bool hypervisor;
         _cleanup_free_ char *hvtype = NULL;
+        _cleanup_free_ char *cpuinfo_contents = NULL;
         int r;
 
         /* Try high-level hypervisor sysfs file first:
@@ -164,6 +165,16 @@ int detect_vm(const char **id) {
         }
 
 #endif
+
+        /* Detect User-Mode Linux by reading /proc/cpuinfo */
+        r = read_full_file("/proc/cpuinfo", &cpuinfo_contents, NULL);
+        if (r < 0)
+                return r;
+        if (strstr(cpuinfo_contents, "User Mode Linux")) {
+                *id = "uml";
+                return 1;
+        }
+
         return 0;
 }
 
-- 
1.8.3.2.736.g869de25