cc04573 Apr 17, 2018
@rwmjones @gaowanlong
600 lines (423 sloc) 18.5 KB
TODO list for libguestfs
This list contains random ideas and musings on features we could add
to libguestfs in future.
The API needs more test coverage, particularly lesser-used system
The big unresolved issue is UID/GID mapping between guest filesystem
IDs and the host. It's not easy to automate this because you need
extra details about the guest itself in order to get to its
UID->username map (eg. /etc/passwd from the guest).
Haskell bindings
Complete the Haskell bindings (see discussion on haskell-cafe).
PHP bindings
Add bindtests to PHP bindings.
Complete bind tests
Complete the bind tests - must test the return values and error cases.
virt-inspector - make libvirt XML
It should be possible to generate libvirt XML from virt-inspector
data, at least partially. This would be just another output type so:
virt-inspector --libvirt guest.img
Note that recent versions of libvirt/virt-install allow guests to be
imported, so this is not so useful any more.
Ideas for extra commands
General glibc / core programs:
ext2 properties:
fts(3) / ftw(3)
sh-in, sh-out: run shell command with large input/output
debug sh-in, debug sh-out: debug versions of the above
Other initrd-* commands
Such as:
virt-rescue pty
Note that pty requires cooperation inside the C code too (there are
two sides to a pty, and one has to be handled after the fork).
[I tried to implement this in the new C virt-rescue, but it doesn't
work. qemu is implementing its own ptys, and they are broken. Need
to fix qemu.]
Port to Windows
"Port to Windows" means different things to different people.
The easiest is to port the library to Windows, but reuse the Linux
appliance/daemon. This would allow people to use libguestfs on
Windows hosts and link libguestfs to Windows programs. Doing this is
just a matter of chugging through the code fixing portability issues,
using gnulib as far as possible as the portability layer.
The hardest is probably a port of the daemon to Windows. The reason
to do this is so that you can use the native NTFS drivers (in Windows)
in order to edit Windows guests. Although back in 2009 we did some
work on this, I am now dubious about the utility of this, since
ntfs-3g works very well. See also discussion on list:
For multi-level disk images such as live CDs:
It's possible with libguestfs to recursively look for anything that
might be a filesystem, mount-{,loop} it and look in those, revealing
anything in a disk image.
However this won't work easily for VM disk images in the disk image.
One would have to download those to the host and launch another
libguestfs instance.
[Not sure this is such a good idea. See also live CD inspection idea below.]
Map filesystems to disk blocks
Map files/filesystems/(any other object) to the actual disk
blocks they occupy.
And vice versa.
Is it even possible?
See also contribs/visualize-alignment/
Integration with host intrusion systems
Perfect way to monitor VMs from outside the VM. Look for file
hashes, log events, login/logout etc.
See also: virt-aide;
Tips for new users in guestfish
$ guestfish
Tip: You need to 'add disk.img' or 'alloc disk.img nn' to make a new image.
Type 'notips' to disable tips permanently.
><fs> add mydisk
Tip: You need to type 'run' before you can see into the disk image.
><fs> run
Tip: Use 'list-filesystems' to see what filesystems are available.
><fs> list-filesystems
Tip: Use 'mount fs /' to mount a filesystem.
><fs> mount /dev/vda1 /
Tip: Use 'll /' to view the filesystem or ...
><fs> ll /
Could we make guestfish interactive if commands are used without params?
><fs> sparse
[[Prints man page]]
Image name? disk.img
Size of image? 10M
Better support for encrypted devices
Currently LUKS support only works if the device contains volume
groups. If it contains, eg., partitions, you cannot access them.
We would like to add:
- Direct access to the /dev/mapper device (eg. if it contains
anything apart from VGs).
Display image as PS
Display the structure of an image file as a PS.
Greater use of blkid / libblkid
There are various useful functions in libblkid for listing partitions,
devices etc which we are essentially duplicating in the daemon. It
would make more sense to just use libblkid for this.
There are some places where we call out to the 'blkid' program. This
might be replaced by direct use of the library (if this is easier).
But it is very hard to be compatible between RHEL6 and RHEL5 when
using the library directly.
Eric Sandeen pointed out the blktrace tool which is a better way of
capturing traces than using patched qemu (see
contrib/visualize-alignment). We would still use the same
visualization tools in conjunction with blktrace traces.
guestfish parsing
At the moment guestfish uses an ad hoc parser which has many
shortcomings. We should change to using a lex/yacc-based scanner and
parser (there are better parsers out there, but yacc is sufficient and
very widely available).
The scanner must deal with the case of parsing a whole command string,
eg. for a command that the user types in:
><fs> add-drive-opts "/tmp/foo" readonly:true
and also with parsing single words from the command line:
guestfish add-drive-opts /tmp/foo readonly:true
Note the quotes are for scanning and don't indicate types.
We should also allow variables and expressions as part of this new
parsing code, eg:
set roots inspect-os
set product inspect-get-product-name %{roots[0]}
% is better than $ because of shell escaping and confusion with shell
Can we combine this with ability to set and read environment
variables? Currently guestfish uses many environment variables like
$EDITOR without any corresponding ability to set them.
set EDITOR /usr/bin/emacs
echo $EDITOR # or %{EDITOR}
edit /etc/resolv.conf
More ntfs tools
ntfsprogs actually has a lot more useful tools than we currently
use. Interesting ones are:
ntfscluster: display file(s) that occupy a cluster or sector
ntfsinfo: print various information about NTFS volume and files
ntfs streams: extract alternate streams from NTFS files
ntfsck: checker for NTFS filesystems
Undelete files
Two useful tools:
- ext2undelete
- ntfsundelete
More mkfs_opts options
Useful options to offer:
- Set label.
- Set UUID.
Use /proc/self/mountinfo
This file contains lots of interesting information about
what is mounted and where. eg:
16 21 0:3 / /proc rw,relatime - proc /proc rw
17 21 0:16 / /sys rw,relatime - sysfs /sys rw,seclabel
18 23 0:5 / /dev rw,relatime - devtmpfs udev rw,seclabel,size=1906740k,nr_inodes=476685,mode=755
26 21 253:3 / /home rw,relatime - ext4 /dev/mapper/vg-lv_home rw,seclabel,barrier=1,data=ordered
This could be used instead of current hairy code to parse the output
of the 'mount' command. We could add new APIs to return kernel mount
options, type of filesystem at a mountpoint etc.
guestfish drive letters
There should be an option to mount all Windows drives as separate
paths, like C: => /c/, D: => /d/ etc.
More inspection features
- last shutdown time
- DHCP address
- last time the software was updated
- last user who logged in
- lastlog, last, who
Integrate virt-inspector with CMDBs
Either integrate virt-inspector with Configuration Management
Databases (CMDBs) or at least check that virt-inspector produces the
right range of data so that integration would be possible. The
standards for CMDBs come from the DMTF, see eg:
Efficient way to visit all files
A naive method would look like:
g#visit ~return_stats:true "/" (
fun pathname stat ->
However this has two disadvantages:
- requires hand-written custom bindings in each language
- unclear about locking, thread-safety and re-entrancy of handle g
A better way would be to have some sort of explicit "download all
filenames and stat structures", which could then be iterated over:
let files = g#find_opts ~return_stats:true "/" in
List.iter (
fun pathname stat ->
The problem with this is that 'files' is going to be larger than a
protocol buffer.
This leads to thinking about changes to the protocol / generator to
make this simpler. The proposal would be to add RBigStringList,
RBigStructList [or RBig (Ranytype ...)]. These would work like
FileOut, in that they would use file streaming to stream XDR
structures (probably written to a file on the library side).
Generated code would hide most of the implementation.
We also need to think about security issues: is it possible for the
daemon to keep sending back data forever, and if so what happens on
the library side.
[Users can now use virt-ls to solve some of these problems, but it is
not a general solution at the API level]
Interactive disk creator
An interactive disk creator program.
Backend for disconnected operation
"Librarian" has an idea that he should be able to attach to a regular
appliance, but disconnect from it and reconnect to it later. This
would be some sort of modified backend (see link above).
The complexity here is that we would no longer have access to
stdin/stdout (or we'd have to direct that somewhere else).
libosinfo mappings for virt-inspector
Return libosinfo mappings from inspection API.
virt-sysprep ideas
- other Spacewalk / RHN IDs (?)
- Windows sysprep
(see: )
- (librarian suggests ...)
. run external guestfish script virt-sysprep --fish=/tmp/
- if drives are encrypted, then dm-crypt key should be changed
and drives all re-encrypted
- secure erase of inodes etc using scrub (Steve Grubb)
- fix the virt-sysprep fs-uuids plugin
- virt-sysprep should be able to zero-free space on the disks (a bit
like virt-sparsify). This is a security measure to stop people
trying to read the deleted files.
Kazuo Moriwaka adds:
- swap devices (both of block device and file) should be wiped. This may
good for security purpose, and size. I found virt-sparsify can clear
swap partition.
- --script is nice. Defining default sysprep script directory
like /usr/lib/guestfs/sysprep-scripts.d/ may be useful to integrate
other package maintainer(or ISV)'s effort.
- To achieve better (or crazy) coverage, a simple examination will be
Install the same kickstart into VM twice, and diff the trees.
Many autogenerated IDs and configs can be found :)
As well as 'virt-sysprep' there is a case for a 'virt-customize' tool
which can customize templated guests. This would be useful within
companies/organizations that want to offer multiple guests, but all
customized with the organization logo etc. Some ideas:
- change the background image to some custom desktop
- change the sign-on messages (/etc/ etc)
- Windows login script/service
Note that virt-sysprep has gradually gained some of these features,
eg. setting hostname, changing passwords. Since this precedent has
now been set, it could do more of the same.
virt-make-fs and virt-win-reg need to not be in Perl
Probably they should be in C or OCaml.
Integrate snap-type functionality in inspection tools
Mo Morsi's "snap" program lets you describe a guest as the list of
packages (eg. RPMs) installed + changes made to those RPMs + files
This results in a compact description of the guest. He even managed
to do a kind of migration of guests by simply recreating the guest
from the description on the target machine.
It would be ideal to integrate this and/or use inspection to do this.
Ongoing code cleanups
Examine every use of 'int' in C code for signed overflow problems.
All file descriptors in the library and daemon should normally be
opened with O_CLOEXEC. Therefore we need to examine every call to:
- open, openat
- creat
- pipe (see also: pipe2)
- dup, dup2 (see also: dup3)
- socket, socketpair
- accept (see also: accept4)
- signalfd, timerfd, epoll_create
virt-sparsify enhancements
'virt-sparsify --whitelist' option to generate skeletons (for
debugging, bug forensics, diagnosis). The whilelist option would
specify a list of files to be *preserved*. All other files in the
image would be replaced by equivalent files of zeroes, thus minimizing
the size of the debug image that needs to be shipped to us by the
Sort out partitioning
Ignoring some legacy APIs, we currently have a mixed selection of
'part-*' APIs, implemented using parted. We don't like parted or
libparted very much, and would love to replace it with something else.
The part-* APIs are quirky, but not too bad and we should maintain and
extend them instead of making another set of APIs.
One option is to write "libmbr" and "libgpt" libraries that would just
do MBR and GPT respectively, and do it directly and do it well. They
wouldn't try to abstract anything (so, unlike libparted). We could
then reimplement the part-* APIs on top of these hopefully sensible
libraries. This is a lot of work.
Another option is to look for tools or libraries to replace parted.
For GPT there is a fairly obvious candidate: Rod Smith's GPT fdisk
( Rod has spent a lot of time
studying GPT, and seems to know more about it than any sane man
should. There is a command line tool designed for scripts called
'sgdisk'. The tools are packaged for many Linux distros. Even if
this approach works, it doesn't solve the MBR problem, so likely we'd
have to write a library for that (or perhaps go back to sfdisk but
using a very abstracted interface over sfdisk).
Reimplement some APIs to avoid protocol limits
Mostly this item was done (eg. commits a69f44f56f and before). The
most notable API with a protocol limit remaining is:
- guestfs_readdir
Reimplement virt-win-reg to use this API. (This is difficult because
the Perl libraries underneath access the hivex API directly).
Implement blocking calls. The API for this:
is very poorly designed and essentially impossible for us to use:
particularly if we also want to maintain backwards compatibility with
Ruby 1.8, and/or maintain volatile VALUEs on the stack.
- how can we give users a shell for debugging purposes?
- let notes etc be localized, ie. notes[en]=...
- add a CLI option to print the in-built path/fingerprint(s)
- doing virt-builder then running (eg. via qemu, libvirt?) is common; is
it possible to make this more automatic?
- document:
* how to integrate with ansible, chef [puppet documented already]
* how to import to EC2
- /etc/resolv.conf handling works but is best described as a hack:
- let's make UML work
+ SLIRP is insecure, but we could allow just a bare web proxy which
gets proxied over virtio-serial to the outside world (except
virtio-serial can't be multiplexed)
- sometimes (not always) aug_init takes ages, why?
Midnight Commander (mc) extension
Write an extension for mc that would let people browse into
filesystems. See
Improvements in virt-log
- Make it faster, especially if the user wants to grep the output.
- Support Windows guests, see
Subsecond handling in virt-diff, virt-ls
Handle nanoseconds properly. You should be able to specify them on
the command line and display them.
virt-v2v -o rhv-upload
* Set or disable the ticket timeout. The default is going to be
increased (from current 60 seconds), so maybe we won't have to
set it. See also:
* qcow2 cannot be supported yet because there is not yet any
concept in imageio of read+write handles.
* preallocated cannot be supported yet because imageio doesn't
know how to zero the image efficiently, instead it runs an
fallocate process which writes to every block and that takes
many minutes.
* Really check what insecure/rhv_cafile do and implement it correctly.
* Measure and resolve performance problems.
* Allocated image size is unknown for v2v uploads, but imageio needs
to know it. We pass initial_size == provisioned_size == virtual size.
That can't be fixed from the v2v side.
* There are unresolved issues about how to clean up disks on failure.