I have been having this same issue for some time and finally found a fix.

Here is what I posted to the bug tracker in sourceforge.

While listing S3 keys: CURL error: Failed writing body (CURLcode 23)
taper: Error writing label DailySet1/010 to device

Had this error any time amanda was attempting to write a new backup to an
S3 slot that previously had data on it.

I found that if I change s3-device.c to have the same s3_list_keys function
to be the same as others in the file the issue went away.

delete_file(S3Device *self,
int file)
{
gboolean result;
GSList *keys;
char *my_prefix = g_strdup_printf("%sf%08x-", self->prefix, file);

result = s3_list_keys(self->s3, self->bucket, self->prefix, "-",
&keys);
if (!result) {


Not sure whay the my_prefix is trying to do but by removing it from the
s3_list_keys it fixed my issue and now backups work correctly.



So edit s3-device.c and change the line in delete_file section to look like 
this: 
result = s3_list_keys(self->s3, self->bucket, self->prefix, "-",
&keys);

once that is done. do a make all and a make install.

That should fix your issues.

Derrick

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