Bug 730248

Summary:	'guestfish --remote run' hangs in a shell command substitution context
Product:	Red Hat Enterprise Linux 6	Reporter:	Richard W.M. Jones <rjones>
Component:	libguestfs	Assignee:	Richard W.M. Jones <rjones>
Status:	CLOSED ERRATA	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	medium	Docs Contact:
Priority:	low
Version:	6.1	CC:	jzheng, leiwang, mbooth, virt-maint
Target Milestone:	rc
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	libguestfs-1.7.17-26.el6	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:	592910	Environment:
Last Closed:	2011-12-06 10:32:04 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Bug Depends On:
Bug Blocks:	592910

Description Richard W.M. Jones 2011-08-12 09:55:11 UTC

+++ This bug was initially created as a clone of Bug #592910 +++

Description of problem:
running 'guestfish --remote run' in a shell command substitution, i.e., `` or $()
would cause the command to hang.

Version-Release number of selected component (if applicable):
guestfish 1.3.13

How reproducible:
Always

Steps to Reproduce:
1. $ eval `guestfish -a test.img --listen`
2. a=`guestfish --remote run`
  
Actual results:
we get hang with step 2

Expected results:
the command should return on completion.

Additional info:

--- Additional comment from rjones on 2010-05-17 06:59:01 EDT ---

Easy to reproduce.

Something about guestfs_launch interferes with
stdout in a way which is incompatible with the remote
protocol.

Note this *doesn't* happen with any other command.  For example:

$ a=`guestfish --remote list-devices`
$ echo $a
/dev/vda
$ a=`guestfish --remote ping-daemon`
$ echo $a

--- Additional comment from rjones on 2010-05-17 07:01:11 EDT ---

Created attachment 414520 [details]
strace

Output from:

strace -o strace.log -f -s 1024 sh -c 'a=`guestfish --remote run`'

--- Additional comment from jzheng on 2011-08-12 05:41:59 EDT ---

Can this one get at least a documentation fix?

Comment 1 Richard W.M. Jones 2011-08-12 10:12:01 UTC

Documentation fix:

http://git.annexia.org/?p=libguestfs.git;a=commitdiff;h=6cabc1cd02e181063596b48df55c3f6db51a6bb9

Comment 3 Jinxin Zheng 2011-08-23 09:14:29 UTC

Documented in man page for guestfish:

--
   REMOTE CONTROL RUN COMMAND HANGING
       Using the "run" (or "launch") command remotely in a command substitution context hangs, ie. don’t do (note the backquotes):

        a=`guestfish --remote run`

       Since the "run" command produces no output on stdout, this is not useful anyway.

Comment 4 errata-xmlrpc 2011-12-06 10:32:04 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2011-1512.html