Do not error out on empty files, just ignore them. This can be easily reproduced by touch'ing an empty file in the directory of an appliance created with --prepare. --- src/mode_build.ml | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/src/mode_build.ml b/src/mode_build.ml index b5f5fa6..8a06012 100644 --- a/src/mode_build.ml +++ b/src/mode_build.ml @@ -46,6 +46,7 @@ and file_content = | Packages | Hostfiles | Excludefiles +| Empty let rec string_of_file_type = function | GZip c -> sprintf "gzip %s" (string_of_file_content c) @@ -56,6 +57,7 @@ and string_of_file_content = function | Packages -> "packages" | Hostfiles -> "hostfiles" | Excludefiles -> "excludefiles" + | Empty -> "empty" let rec build debug (copy_kernel, format, host_cpu, @@ -250,6 +252,8 @@ and read_appliance debug basedir appliance = function (* Depending on the file type, read or unpack the file. *) let appliance = match file_type with + | Uncompressed Empty | GZip Empty | XZ Empty -> + appliance | Uncompressed ((Packages|Hostfiles|Excludefiles) as t) -> let chan = open_in file in let lines = input_all_lines chan in @@ -294,7 +298,7 @@ and update_appliance appliance lines = function String.sub path 1 (n-1) ) lines in { appliance with excludefiles = appliance.excludefiles @ lines } - | Base_image -> assert false + | Base_image | Empty -> assert false (* Determine the [file_type] of [file], or exit with an error. *) and get_file_type file = @@ -331,6 +335,7 @@ and get_file_content file buf len = else if len >= 2 && buf.[0] = '/' then Hostfiles else if len >= 2 && buf.[0] = '-' then Excludefiles else if len >= 1 && isalnum buf.[0] then Packages + else if len = 0 then Empty else error "%s: unknown file type in supermin directory" file and get_compressed_file_content zcat file = -- 2.17.2

tar defaults to 10K as block size, and thus it pads the created archives to multiples of that size using zero's. Hence, when creating an archive with no files, it will be 10K zero's, that is compressed by gzip, resulting in few bytes. The issue happens later, during the build phase: base.tar.gz is correctly detected as gz, and zcat is run to detect its content: since the empty tar was 10K of zero's, the buffer in get_compressed_file_content will be filled by zero's, and get_file_content will fail to detect anything. As solution, at least for our own base.tar.gz: in case there are no config files to copy, do not create base.tar.gz at all. --- src/mode_prepare.ml | 43 ++++++++++++++++++++++++++----------------- 1 file changed, 26 insertions(+), 17 deletions(-) diff --git a/src/mode_prepare.ml b/src/mode_prepare.ml index 7759c58..70f9dd4 100644 --- a/src/mode_prepare.ml +++ b/src/mode_prepare.ml @@ -149,20 +149,29 @@ let prepare debug (copy_kernel, format, host_cpu, printf "supermin: there are %d config files\n" (List.length config_files); - let files_from = - (* Put the list of config files into a file, for tar to read. *) - let files_from = tmpdir // "files-from.txt" in - let chan = open_out files_from in - List.iter (fprintf chan ".%s\n") config_files; (* "./filename" *) - close_out chan; - - files_from in - - (* Write base.tar.gz. *) - let base = outputdir // "base.tar.gz" in - if debug >= 1 then printf "supermin: writing %s\n%!" base; - let cmd = - sprintf "tar%s -C %s -zcf %s -T %s" - (if debug >=1 then " -v" else "") - (quote dir) (quote base) (quote files_from) in - run_command cmd; + if config_files <> [] then ( + (* There are config files to copy, so create the list with them, + * and then compress them with tar. + *) + let files_from = + (* Put the list of config files into a file, for tar to read. *) + let files_from = tmpdir // "files-from.txt" in + let chan = open_out files_from in + List.iter (fprintf chan ".%s\n") config_files; (* "./filename" *) + close_out chan; + + files_from in + + (* Write base.tar.gz. *) + let base = outputdir // "base.tar.gz" in + if debug >= 1 then printf "supermin: writing %s\n%!" base; + let cmd = + sprintf "tar%s -C %s -zcf %s -T %s" + (if debug >=1 then " -v" else "") + (quote dir) (quote base) (quote files_from) in + run_command cmd; + ) + else ( + (* No config files to copy, so do not create base.tar.gz. *) + if debug >= 1 then printf "supermin: not creating base.tar.gz\n%!"; + ) -- 2.17.2