similar to: [PATCH nbdkit v3] New tmpdisk plugin.

Unfinished (needs tests). This is my attempt to make a "remote tmpfs" plugin as outlined in this prior email: https://www.redhat.com/archives/libguestfs/2020-March/msg00134.html Although it would be possible to construct something a bit like this using existing plugins and filters (perhaps with some new features in those filters) I think it may be nicer to have a dedicated plugin for

This can be used for creating temporary disks to thin clients, as a kind of "remote tmpfs". See also: https://www.redhat.com/archives/libguestfs/2020-March/msg00134.html --- plugins/data/nbdkit-data-plugin.pod | 1 + plugins/file/nbdkit-file-plugin.pod | 1 + plugins/linuxdisk/nbdkit-linuxdisk-plugin.pod | 7 +- plugins/memory/nbdkit-memory-plugin.pod |

An evolution of v1 here: https://www.redhat.com/archives/libguestfs/2020-April/msg00035.html I want to generalize the tmpdisk plugin, particularly so you can use commands like ‘qemu-img create’ or even ‘virt-builder’. (Actually virt-builder really works - I tested it - but of course it causes a 30+ second delay when connecting to the server.) You can now use commands such as: nbdkit tmpdisk

v2 was here: https://www.redhat.com/archives/libguestfs/2020-April/msg00075.html In v3: - Add [VAR=VALUE ...] to manual. - Various minor improvements to the manual. - Work (at least, in theory - not tested) with block devices or symlinks. I didn't document this because it's hard to ensure these files or block devices would be cleaned up, so here be dragons. - Remove O_NOCTTY. -

Patch 1/2 is uncontroversial. Patch 2/2 is an interesting idea I had to generalize this plugin. It already uses a complete embedded shell script to do most of the work. What if, instead of making special cases for "type" and "label" params, we simply turn any other plugin parameters into script variables? This part of it works fine. However there is another problem which is

Another interesting thing you can do with this plugin: https://rwmj.wordpress.com/2019/02/19/nbdkit-linuxdisk-plugin/ v2: - Fix inconsistent tab/space. - All 3 plugins now contain a block of text pointing to the other 2 plugins. - TMDIR -> TMPDIR - Unlink the temporary file and other cleanups along error paths. - fclose -> pclose, and check the return value for errors. -

I like this change. I think we were overloading the config_complete method before to do two different things (complete configuration; do any allocation/housekeeping necessary before we can start serving). The only questions in my mind are whether we want this before 1.18, and whether the name ("get_ready") is a good one. Rich.

Turns out Japanese trains are good for coding! In supermin we have a bunch of code to create the libguestfs appliance. It creates it directly using libext2fs (part of e2fsprogs). We can use the same technique to create ext2 virtual disks in nbdkit, which is what this new plugin does. Why a new plugin instead of modifying the floppy plugin? See the 4/4 commit message for an explanation. The

For v3 I reimplemented this using mke2fs -d. This obviously makes the implementation a whole lot simpler, but cannot support multiple directory merging. Patches 1-3 are the same as before. I've also reproduced the notes from v2 below. v2: - Fix inconsistent tab/space. - All 3 plugins now contain a block of text pointing to the other 2 plugins. - TMDIR -> TMPDIR - Unlink the

There is a small test provided. I tested this a lot more locally and it seems pretty robust. Rich.

For review only, this needs some clean up and more tests. My eyes are going cross-eyed looking at the calculate_offset_of_entry function, so time to take a break ... Rich.

Here's changes to the file plugin (which I'm happy with) and a new exportname filter (which is still at RFC stage; I need to finish implementing strict mode in .open, and add tests). I also discovered that we really want .list_exports and .open to know when they are used on plaintext vs. tls clients for --tls=on, and we may want to split out a new .default_export callback rather than

Since v1: - rework .can_cache to be tri-state, with default of no advertisement (ripple effect through other patches) - add a lot more patches in order to round out filter support And in the meantime, Rich pushed NBD_CMD_CACHE support into libnbd, so in theory we now have a way to test cache commands through the entire stack. Eric Blake (24): server: Internal hooks for implementing

This patch isn't complete (patch 6/6 isn't finished) so it's just for discussion, although it does compile and run. This introduces to nbdkit a concept of "filters" which can be placed in front of plugins to modify their behaviour. Some examples where you might use filters: * Serve a subset of the data, such as (offset, range) or a single partition from a disk image.

The first four patches are fairly routine clean up and can be reviewed/applied on their own. The fifth patch is problematic as described below. At the moment if you want to proxy through to qemu-nbd (eg. for handling qcow2 files) it's rather complicated and you end up having to manage the sockets and clean up yourself. However the library we use for the proxying supports a perfectly good

This is still tentative and needs a lot of work, but: - partition filter works, supporting MBR & GPT - prepare and finalize methods fixed - open method can now be changed (allowing readonly flag to be modified) - thread_model can be limited I believe I made most of the changes which were previously suggested in email. I think the only one I didn't was preventing inclusion of both

Eric, you'll probably find the design "interesting" ... It does work, for me at least. Rich.

I fixed the deadlock - turned out to be an actual bug in the nbd plugin (see patch 8). I changed the command syntax so it's now: nbdkit nbd command=qemu arg=-f arg=qcow2 arg=/path/to/disk.qcow2 Nir wrote: 18:08 < nsoffer> rwmjones: regarding the nbd proxy patches, did you have specific flow that help us? 18:08 < nsoffer> rwmjones: or this is just a way to support qcow2 in the

I'm pushing the first one as blatantly obvious. The second one is also simple enough, but not enough of a bug for me to push tonight. The third is something I noticed while working on sh, but is really more about docs vs. plugins in general. There, we could either change the code to match the docs (breaking backwards behavior for a plugin that set .errno_is_preserved=2) [what my patch did],

Experimental and only very lightly tested so far. Rich.