Libguestfs - May 2020 - [common PATCH] mltools: add run_in_guest_command helper

Add an helper function to run a command in the guest, checking for the
host/guest compatibility.  This is mostly extracted from the internal
do_run helper currently in the Customize_run module of virt-customize.
---
 mltools/tools_utils.ml  | 50 +++++++++++++++++++++++++++++++++++++++++
 mltools/tools_utils.mli | 10 +++++++++
 2 files changed, 60 insertions(+)

diff --git a/mltools/tools_utils.ml b/mltools/tools_utils.ml
index 1271802..d54ec58 100644
--- a/mltools/tools_utils.ml
+++ b/mltools/tools_utils.ml
@@ -679,3 +679,53 @@ let with_timeout op timeout ?(sleep = 2) fn         loop ()
   in
   loop ()
+
+let run_in_guest_command g root ?logfile ?incompatible_fn cmd +  (* Is the
host_cpu compatible with the guest arch?  ie. Can we
+   * run commands in this guest?
+   *)
+  let guest_arch = g#inspect_get_arch root in
+  let guest_arch_compatible = guest_arch_compatible guest_arch in
+  if not guest_arch_compatible then (
+    match incompatible_fn with
+    | None -> ()
+    | Some fn -> fn ()
+  )
+  else (
+    (* Add a prologue to the scripts:
+     * - Pass environment variables through from the host.
+     * - Optionally send stdout and stderr to a log file so we capture
+     *   all output in error messages.
+     * - Use setarch when running x86_64 host + i686 guest.
+     *)
+    let env_vars +      List.filter_map (
+        fun name ->
+          try Some (sprintf "export %s=%s" name (quote (Sys.getenv
name)))
+          with Not_found -> None
+      ) [ "http_proxy"; "https_proxy";
"ftp_proxy"; "no_proxy" ] in
+    let env_vars = String.concat "\n" env_vars ^ "\n" in
+
+    let cmd +      match Guestfs_config.host_cpu, guest_arch with
+      | "x86_64",
("i386"|"i486"|"i586"|"i686") ->
+        sprintf "setarch i686 <<\"__EOCMD\"
+%s
+__EOCMD
+" cmd
+      | _ -> cmd in
+
+    let logfile_redirect +      match logfile with
+      | None -> ""
+      | Some logfile -> sprintf "exec >>%s 2>&1"
(quote logfile) in
+
+    let cmd = sprintf "\
+%s
+%s
+%s
+" (logfile_redirect) env_vars cmd in
+
+    debug "running command:\n%s" cmd;
+    ignore (g#sh cmd)
+  )
diff --git a/mltools/tools_utils.mli b/mltools/tools_utils.mli
index ab70f58..102abff 100644
--- a/mltools/tools_utils.mli
+++ b/mltools/tools_utils.mli
@@ -212,3 +212,13 @@ val with_timeout : string -> int -> ?sleep:int ->
(unit -> 'a option) -> 'a
     calls {!error} and the program exits.  The error message will
     contain the diagnostic string [op] to identify the operation
     which timed out. *)
+
+val run_in_guest_command : Guestfs.guestfs -> string -> ?logfile:string
-> ?incompatible_fn:(unit -> unit) -> string -> unit
+(** [run_in_guest_command g root ?incompatible_archs_fn cmd]
+    runs a command in the guest, which is already mounted for the
+    specified [root].  The command is run directly in case the
+    architecture of the host and the guest are compatible, optionally
+    calling [?incompatible_fn] in case they are not.
+
+    [?logfile] is an optional file in the guest to where redirect
+    stdout and stderr of the command. *)
-- 
2.25.4

On Mon, May 04, 2020 at 03:22:37PM +0200, Pino Toscano
wrote:
> Add an helper function to run a command in the guest, checking for the
> host/guest compatibility.  This is mostly extracted from the internal
> do_run helper currently in the Customize_run module of virt-customize.
> ---
>  mltools/tools_utils.ml  | 50 +++++++++++++++++++++++++++++++++++++++++
>  mltools/tools_utils.mli | 10 +++++++++
>  2 files changed, 60 insertions(+)
> 
> diff --git a/mltools/tools_utils.ml b/mltools/tools_utils.ml
> index 1271802..d54ec58 100644
> --- a/mltools/tools_utils.ml
> +++ b/mltools/tools_utils.ml
> @@ -679,3 +679,53 @@ let with_timeout op timeout ?(sleep = 2) fn >      
loop ()
>    in
>    loop ()
> +
> +let run_in_guest_command g root ?logfile ?incompatible_fn cmd > +  (*
Is the host_cpu compatible with the guest arch?  ie. Can we
> +   * run commands in this guest?
> +   *)
> +  let guest_arch = g#inspect_get_arch root in
> +  let guest_arch_compatible = guest_arch_compatible guest_arch in
> +  if not guest_arch_compatible then (
> +    match incompatible_fn with
> +    | None -> ()
> +    | Some fn -> fn ()
> +  )
> +  else (
> +    (* Add a prologue to the scripts:
> +     * - Pass environment variables through from the host.
> +     * - Optionally send stdout and stderr to a log file so we capture
> +     *   all output in error messages.
> +     * - Use setarch when running x86_64 host + i686 guest.
> +     *)
> +    let env_vars > +      List.filter_map (
> +        fun name ->
> +          try Some (sprintf "export %s=%s" name (quote
(Sys.getenv name)))
> +          with Not_found -> None
> +      ) [ "http_proxy"; "https_proxy";
"ftp_proxy"; "no_proxy" ] in
> +    let env_vars = String.concat "\n" env_vars ^ "\n"
in
> +
> +    let cmd > +      match Guestfs_config.host_cpu, guest_arch with
> +      | "x86_64",
("i386"|"i486"|"i586"|"i686") ->
> +        sprintf "setarch i686 <<\"__EOCMD\"
> +%s
> +__EOCMD
> +" cmd
> +      | _ -> cmd in
> +
> +    let logfile_redirect > +      match logfile with
> +      | None -> ""
> +      | Some logfile -> sprintf "exec >>%s 2>&1"
(quote logfile) in
> +
> +    let cmd = sprintf "\
> +%s
> +%s
> +%s
> +" (logfile_redirect) env_vars cmd in
> +
> +    debug "running command:\n%s" cmd;
> +    ignore (g#sh cmd)
> +  )
> diff --git a/mltools/tools_utils.mli b/mltools/tools_utils.mli
> index ab70f58..102abff 100644
> --- a/mltools/tools_utils.mli
> +++ b/mltools/tools_utils.mli
> @@ -212,3 +212,13 @@ val with_timeout : string -> int -> ?sleep:int
-> (unit -> 'a option) -> 'a
>      calls {!error} and the program exits.  The error message will
>      contain the diagnostic string [op] to identify the operation
>      which timed out. *)
> +
> +val run_in_guest_command : Guestfs.guestfs -> string ->
?logfile:string -> ?incompatible_fn:(unit -> unit) -> string -> unit
> +(** [run_in_guest_command g root ?incompatible_archs_fn cmd]
> +    runs a command in the guest, which is already mounted for the
> +    specified [root].  The command is run directly in case the
> +    architecture of the host and the guest are compatible, optionally
> +    calling [?incompatible_fn] in case they are not.
> +
> +    [?logfile] is an optional file in the guest to where redirect
> +    stdout and stderr of the command. *)
Pretty much a straightforward copy of the virt-sysprep function.

ACK.

Thanks,

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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