Re: [Libguestfs] [PATCH nbdkit v3] tmpdisk: Pass any parameters as shell variables to the command.

This allows us to be much more flexible about what commands can be used. It also means we do not need to encode any special behaviour for type or label parameters. --- plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod | 115 ++++++++++---- tests/Makefile.am | 2 + plugins/tmpdisk/tmpdisk.c | 184 ++++++++++++++++------ plugins/tmpdisk/default-command.sh.in | 6 + tests/test-tmpdisk-command.sh | 52 ++++++ 5 files changed, 278 insertions(+), 81 deletions(-)

+=head2 Serve a fresh operating system to each client + + nbdkit tmpdisk 16G os=fedora-31 \ + command=' virt-builder -o "$disk" --size ${size}b "$os" ' + +=head2 Serve a throwaway snapshot of a base image to each client + +You could create a base image using L<virt-builder(1)> or a similar +tool, and then serve different throwaway snapshots to each client: + + virt-builder fedora-31 -o /var/tmp/base.img + nbdkit tmpdisk size=0 base=/var/tmp/base.img \ + command=' cp --sparse=always "$base" "$disk" ' +

+/* For block devices, stat->st_size is not the true size. */ +static int64_t +block_device_size (int fd) +{ + off_t size; + + size = lseek (fd, 0, SEEK_END); + if (size == -1) { + nbdkit_error ("lseek: %m"); + return -1; + } + + return size; +}

+ /* The command could set $disk to a regular file or a block device + * (or a symlink to either), so we must check that here. + */ + if (S_ISBLK (statbuf.st_mode)) { + h->size = block_device_size (h->fd); + if (h->size == -1) + goto error; + } + else /* Regular file. */ + h->size = statbuf.st_size; + nbdkit_debug ("tmpdisk: requested_size = %" PRIi64 ", size = %" PRIi64, + requested_size, h->size); + /* We don't need the disk to appear in the filesystem since we hold * a file descriptor and access it through that, so unlink the disk. * This also ensures it is always cleaned up. */ unlink (disk); + rmdir (dir);

+++ b/tests/test-tmpdisk-command.sh

+source ./functions.sh +set -e +set -x + +requires nbdsh -c 'exit (not h.supports_uri ())' + +# - If multiple parameters appear, last one is used. +# - Test quoting. +# - size=0 because we ignore it in the command itself. +nbdkit -f -v -U - tmpdisk 0 a=2 a=1 b=1024 c="a ' b ' c" \ + command=' +set -x +set -e +if [ $a -ne 1 ]; then exit 1; fi +if [ "$c" != "a '\'' b '\'' c" ]; then exit 1; fi +truncate -s $b "$disk" +' \ + --run ' +nbdsh -u "$uri" -c "assert h.get_size() == 1024" +'