Red Hat Bugzilla – Bug 731742
libguestfs should escape special/non-printing characters in debug output
Last modified: 2012-06-20 02:59:48 EDT
Description of problem: In seabios-0.6.1.2-4.el6.x86_64 from RHEL 6.2 the BIOS prints special control characters to clear the screen etc. Some lame attempt at a splash screen. Unfortunately libguestfs in debug mode (LIBGUESTFS_DEBUG=1) simply echos these characters straight to stderr, meaning that you see the screen being cleared and so on. libguestfs should strip or escape these special characters in its default debug mode. Also we should document this here: http://libguestfs.org/guestfs.3.html#guestfs_event_callback Version-Release number of selected component (if applicable): libguestfs-1.7.17-26.el6.x86_64 How reproducible: 100% Steps to Reproduce: 1. Install seabios-0.6.1.2-4.el6.x86_64 (RHEL 6) 2. Install qemu-kvm-0.12.1.2-2.183.el6.x86_64 (RHEL 6) 3. Run guestfish -a /dev/null run -v Actual results: Observe that early in the debug output the screen is cleared. Expected results: The control characters should be escaped. Additional info: Since this is annoying rather than serious, I'm going to defer it to RHEL 6.3 and make it dependent on the rebase bug.
Upstream commit is 06019bc82e107f7715ebc59e491610e06dad1e39. This is pretty easy to test: guestfish -a /dev/null -v ><fs> run [Lots of appliance boot messages] Now type the command below precisely at the guestfish prompt: debug sh 'echo -e "\\x01\\x01" >&2' There are two possible outputs that can happen for libguestfs in RHEL >= 6.2. If no escaping is being applied (ie. the bug is present), then you will see TWO lines of garbage output: The first line comes from the appliance and is not being escaped. The second line is the output of guestfish which should not be escaped. If escaping is being applied, then the first line ONLY will be escaped: \x1\x1 ^ This is the correct output if the bug has been fixed.
Verified with libguestfs-1.16.2-1.el6.x86_64. 1. Tested as comment 2: [1]. using libguestfs-1.7.17-26.el6.x86_64: ><fs> debug sh 'echo -e "\\x01\\x01" >&2' send_to_daemon: 0x15d61b0 g->state = 3, n = 96 recv_from_daemon: 0x15d61b0 g->state = 3, size_rtn = 0x7fff32ad739c, buf_rtn = 0x7fff32ad7390 /bin/sh -c echo -e "\\x01\\x01" >&2 ><fs> [2]. using libguestfs-1.16.2-1.el6.x86_64 ><fs> debug sh 'echo -e "\\x01\\x01" >&2' libguestfs: send_to_daemon: 96 bytes: 00 00 00 5c | 20 00 f5 f5 | 00 00 00 04 | 00 00 00 4c | 00 00 00 00 | ... guestfsd: main_loop: new request, len 0x5c /bin/sh -c echo -e "\\x01\\x01" >&2 \x1\x1 guestfsd: main_loop: proc 76 (debug) took 0.00 seconds libguestfs: recv_from_daemon: 48 bytes: 20 00 f5 f5 | 00 00 00 04 | 00 00 00 4c | 00 00 00 01 | 00 12 34 01 | ... ><fs> 2. Check with seabios-0.6.1.2-8.el6.x86_64 + qemu-kvm-0.12.1.2-2.209.el6.x86_64: [1] Before the fix, early in the debug output the screen is cleared. [2] After the fix, the control characters are escaped as following: [...] SeaBIOS (version 0.6.1.2-20111101_081028-x86-007.build.bos.redhat.com) Probing EDD (edd=off to disable)... ok \x1b[2J\x1b[2JInitializing cgroup subsys cpuset [...]
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: No Documentation needed
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/RHSA-2012-0774.html