pid1: initialize TERM environment variable correctly

When systemd is started by the kernel, the kernel set the TERM
environment variable unconditionnally to "linux" no matter the console
device used. This might be an issue for dumb devices with no colors
support.

This patch uses default_term_for_tty() for getting a more accurate
value. But it makes sure to keep the user preferences (if any) which
might be passed via the kernel command line. For that purpose /proc
should be mounted.

1 files changed, 37 insertions, 0 deletions

diff --git a/src/core/main.c b/src/core/main.c
index 40d7ff9be5..0a09ff514a 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -1294,6 +1294,35 @@ static int bump_unix_max_dgram_qlen(void) {
         return 1;
 }
 
+static int fixup_environment(void) {
+        _cleanup_free_ char *term = NULL;
+        int r;
+
+        /* When started as PID1, the kernel uses /dev/console
+         * for our stdios and uses TERM=linux whatever the
+         * backend device used by the console. We try to make
+         * a better guess here since some consoles might not
+         * have support for color mode for example.
+         *
+         * However if TERM was configured through the kernel
+         * command line then leave it alone. */
+
+        r = get_proc_cmdline_key("TERM=", &term);
+        if (r < 0)
+                return r;
+
+        if (r == 0) {
+                term = strdup(default_term_for_tty("/dev/console") + 5);
+                if (!term)
+                        return -errno;
+        }
+
+        if (setenv("TERM", term, 1) < 0)
+                return -errno;
+
+        return 0;
+}
+
 int main(int argc, char *argv[]) {
         Manager *m = NULL;
         int r, retval = EXIT_FAILURE;
@@ -1480,6 +1509,14 @@ int main(int argc, char *argv[]) {
                         (void) write_string_file("/proc/sys/kernel/core_pattern", "|/bin/false", 0);
         }
 
+        /* We expect the environment to be set correctly if run inside a
+         * container. */
+        if (arg_system && detect_container() <= 0)
+                if (fixup_environment() < 0) {
+                        error_message = "Failed to fix up PID1 environment";
+                        goto finish;
+                }
+
         /* Initialize default unit */
         r = free_and_strdup(&arg_default_unit, SPECIAL_DEFAULT_TARGET);
         if (r < 0) {