Re: [Libguestfs] [v2v PATCH v2] input_vmx: cleanly reject guests with snapshots when using "-it ssh"

On Sat, Apr 09, 2022 at 08:12:52AM +0200, Laszlo Ersek wrote: > For traversing a backing chain of VMDK descriptor files over ssh, two > things are necessary: > > - qemu-nbd with the ssh block driver, rather than nbdkit-ssh-plugin, > > - a remote SSH URL (for qemu-nbd) without a query string appended, as > qemu-nbd cannot update the last pathname component (for tracking the > relative pathnames of VMDK descriptor files) if a query string is > appended. > > Before commit 7a6f6113a25f ("v2v: -i vmx -it ssh: Replace qemu block ssh > driver with nbdkit-ssh-plugin.", 2019-10-08), we passed the > "?host_key_check=no" query string in the URL to qemu-nbd, so we can't just > return to that, for accessing snapshotted guests with vmx+ssh. > > But, we shouldn't return to qemu-nbd for vmx+ssh even without a query > string, as that would undo the other benefit(s) of commit 7a6f6113a25f. > > Instead, clearly document that snapshotted guests are not supported over > vmx+ssh, and cleanly reject this situation in the code as well. Recommend > the two alternative transports that allow the user to convert such guests. > > Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1774386 > Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; > --- > > Notes: > v2: > > - in the manual, centralize the description in a new NOTES section, and > reference that section from "-i vmx -it ssh" and "INPUT FROM VMWARE > VMX" [Rich] > > - in the code, bail out with error (f_"...") rather than failwith, for > enabling translations [Rich] And line wrapping too .. > - in the error message printed from the code, recommend actions to the > user (reference the new NOTES section of the manual) [Rich] > > input/input_vmx.ml | 27 ++++++++------------ > docs/virt-v2v-input-vmware.pod | 18 ++++++++++++- > 2 files changed, 27 insertions(+), 18 deletions(-) > > diff --git a/input/input_vmx.ml b/input/input_vmx.ml > index 9921419b5a85..eed8a4335622 100644 > --- a/input/input_vmx.ml > +++ b/input/input_vmx.ml > @@ -81,23 +81,16 @@ module VMX = struct > > let vmx_path = path_of_uri uri in > let abs_path = absolute_path_from_other_file vmx_path filename in > - let format = "vmdk" in > + let flat_vmdk = PCRE.replace (PCRE.compile "\\.vmdk$") > + "-flat.vmdk" abs_path in > > - (* XXX This is a hack to work around qemu / VMDK limitation > - * "Cannot use relative extent paths with VMDK descriptor file" > - * We can remove this if the above is fixed. > - *) > - let abs_path, format = > - let flat_vmdk = > - PCRE.replace (PCRE.compile "\\.vmdk$") "-flat.vmdk" abs_path in > - if remote_file_exists uri flat_vmdk then (flat_vmdk, "raw") > - else (abs_path, format) in > - > - (* XXX In virt-v2v 1.42+ importing from VMX over SSH > - * was broken if the -flat.vmdk file did not exist. > - * It is still broken here. > - *) > - ignore format; > + (* RHBZ#1774386 *) > + if not (remote_file_exists uri flat_vmdk) then > + error (f_"This transport does not support guests with snapshots. \ > + Either collapse the snapshots for this guest and try \ > + the conversion again, or use one of the alternate \ > + conversion methods described in \ > + virt-v2v-input-vmware(1) section \"NOTES\"."); > > let server = server_of_uri uri in > let port = Option.map string_of_int (port_of_uri uri) in > @@ -110,7 +103,7 @@ module VMX = struct > let cor = dir // "convert" in > let bandwidth = options.bandwidth in > let nbdkit = Nbdkit_ssh.create_ssh ?bandwidth ~cor ~password > - ~server ?port ?user abs_path in > + ~server ?port ?user flat_vmdk in > let _, pid = Nbdkit.run_unix socket nbdkit in > On_exit.kill pid > ) filenames > diff --git a/docs/virt-v2v-input-vmware.pod b/docs/virt-v2v-input-vmware.pod > index 2c90e0afc7cd..66ca5f00d28a 100644 > --- a/docs/virt-v2v-input-vmware.pod > +++ b/docs/virt-v2v-input-vmware.pod > @@ -51,6 +51,9 @@ to ESXi to read the F<GUEST.vmx> file and associated disks. This > requires that you have enabled SSH access to the VMware ESXi > hypervisor - in the default ESXi configuration this is turned off. > > +This transport is incompatible with guests that have snapshots; refer > +to L</NOTES>. > + > =item B<-ic vpx://...> B<-it vddk> > > =item B<-ic esx://...> B<-it vddk> > @@ -84,6 +87,18 @@ import a guest from VMware vCenter. This is the slowest method. > > =back > > +=head1 NOTES > + > +When accessing the F<I<guest>.vmx> file on ESXi over an SSH connection > +(that is, when using the B<-i vmx> B<-it ssh> options), the conversion The convention -- not written down anywhere :-( -- is to use B<-option> when referencing the option first time in =item, and I<-option> elsewhere. See for example: https://gitlab.com/nbdkit/nbdkit/-/commit/bc0d4f23ce08052db4c9cd3a1a563f5... So here it should be I<-i vmx> I<-it ssh> ... > +will not work if the guest has snapshots (files called > +F<I<guest>-000001.vmdk> and similar). Either collapse the snapshots > +for the guest and retry the conversion with the same > +B<-i vmx> B<-it ssh> options, or leave the snapshots intact and use a > +transport different from SSH: just B<-i vmx>, or > +B<-ic vpx://...> B<-it vddk> or B<-ic esx://...> B<-it vddk>. Refer ... and here too. > +to L<https://bugzilla.redhat.com/1774386>;. > + > =head1 INPUT FROM VMWARE VMX > > Virt-v2v is able to import guests from VMware’s vmx files. > @@ -106,7 +121,8 @@ a C</vmfs/volumes> folder containing the virtual machines. > > If you find a folder of files called F<I<guest>.vmx>, > F<I<guest>.vmxf>, F<I<guest>.nvram> and one or more F<.vmdk> disk > -images, then you can use this method. > +images, then you can use this method. The SSH transport is not usable > +if the guest has snapshots; refer to L</NOTES>. > > =head2 VMX: Guest must be shut down With the B<> changed to I<> it's good to go, thanks, so: Reviewed-by: Richard W.M. Jones <rjones(a)redhat.com&gt;