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Diffstat (limited to 'mailinglist/output_launchpad/1881648')
| -rw-r--r-- | mailinglist/output_launchpad/1881648 | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/mailinglist/output_launchpad/1881648 b/mailinglist/output_launchpad/1881648 new file mode 100644 index 00000000..10d22b14 --- /dev/null +++ b/mailinglist/output_launchpad/1881648 @@ -0,0 +1,31 @@ +`qemu-img info` reports an incorrect actual-size when the underlying posix filesystem has transparent compression + +qemu-img info reports the same thing as `du`*1024: + +$ qemu-img info --output json ./my.qcow2 | jq '."actual-size"' +558619648 + +$ du ./my.qcow2 +545527 ./my.qcow2 + +$ echo $((558619648 / 545527)) +1024 + +and this is correct in terms of bytes on disk, but due to transparent compression implemented by the filesystem, it is not the actual byte count: + +$ du -h --apparent-size ./my.qcow2 +1346568192 my.qcow2 + +But that’s the point of that field, to show the amount of space used by the image on the host. + +The man page documents it as: “disk size: How much space the image file occupies on the host file system (may be shown as 0 if this information is unavailable, e.g. because there is no file system)”, and the QAPI definition of ImageInfo documents the actual-size field as “actual size on disk in bytes of the image”. + +So it is documented as and intended to be the number of bytes used, not the length of the file. + +Max + +This bug has been reported on the Ubuntu ISO testing tracker. + +A list of all reports related to this bug can be found here: +http://iso.qa.ubuntu.com/qatracker/reports/bugs/1881648 + |