Re: Using "xl create" without domain config file

["W. Michael Petullo" <mike@flyn.org>]

[...]

>>> -    if (!S_ISREG(stab.st_mode)) {
>>> -        LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "%s is not a plain file", filename);
>>> +    if (S_ISDIR(stab.st_mode)) {
>>> +        LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "%s is a directory", filename);
>>
>> This is not correct.  If, for example, /dev/tty is specified, it will
>> go wrong.
>>
>> The reason for the restriction to plain files is that those are the
>> only thing on which stat works to provide the size.  If we are to
>> support other objects, we need to change the reading algorithm.
>
> Another alternative would be to special-case the string "/dev/null"
> (in xl, not libxl) and not read a config file at all in that case.

This patch treats /dev/null as a special case.

# HG changeset patch
# Parent 435493696053a079ec17d6e1a63e5f2be3a2c9d0
xl: Allow use of /dev/null with xl create to enable command-line definition

xm allows specifying /dev/null as the domain configuration argument to its
create option; add same functionality to xl. xl treats the configuration
argument /dev/null as a special case.  This allows specifying an entire
domain configuration on the command line.

Signed-off-by: W. Michael Petullo <mike@flyn.org>

diff -r 435493696053 tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c  Fri May 25 08:18:47 2012 +0100
+++ b/tools/libxl/xl_cmdimpl.c  Thu Jun 07 22:40:58 2012 -0500
@@ -1454,10 +1454,13 @@ static int create_domain(struct domain_c

     if (config_file) {
         free(config_data);  config_data = 0;
-        ret = libxl_read_file_contents(&ctx, config_file,
-                                       &config_data, &config_len);
-        if (ret) { fprintf(stderr, "Failed to read config file: %s: %s\n",
-                           config_file, strerror(errno)); return ERROR_FAIL; }
+        // /dev/null represents special case (read config. from command line)
+        if (strcmp(config_file, "/dev/null")) {
+            ret = libxl_read_file_contents(&ctx, config_file,
+                                           &config_data, &config_len);
+            if (ret) { fprintf(stderr, "Failed to read config file: %s: %s\n",
+                               config_file, strerror(errno)); return ERROR_FAIL; }
+        }
         if (!restore_file && extra_config && strlen(extra_config)) {
             if (config_len > INT_MAX - (strlen(extra_config) + 2 + 1)) {
                 fprintf(stderr, "Failed to attach extra configration\n");