Messages in this thread | | | Date | Fri, 26 Jan 2018 07:51:21 -0800 (PST) | From | Victor Kamensky <> | Subject | Re: [PATCH v2 01/15] Documentation: add newcx initramfs format description |
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On Fri, 26 Jan 2018, Henrique de Moraes Holschuh wrote:
> On Thu, 25 Jan 2018, Rob Landley wrote: >> That said, I don't think -h newcx should emit (or recognize) the >> "TRAILER!!!1!" entry. That's kinda silly in-band signaling for 2018: >> files have a length, pipes provide EOF, and each cpiox entry starts with >> 6 bytes of c_magic anyway.
My understanding that TRAILER is really used on tape devices, there is no notion of file end in this case, it is just a stream of bytes from char device.
Thanks, Victor
>> (I stopped toybox from producing the TRAILER >> entry back in june, toybox commit 32550751997d, and the kernel consumes >> the resulting cpio just fine. All the trailer does is prevent you from >> concatenating cpio files, which is a feature multiple people asked me for.) > > Not in the kernel. What TRAILER does in the kernel is to act as a > barrier for the hardlink creation state, which IS a good thing. You > could just specify it as such for "newcx". > > The kernel will continue reading for more entries after TRAILER, so > concatenation is not broken by TRAILER. It is also insensitive to > NUL-padding length (as long as it is 4-byte aligned), which is another > nice feature you could specify for "newcx". > > Also, the kernel does something nothing in userspace ever tried to, > AFAIK: it detects compression signatures along with the CPIO header > signatures, and thus it can take several compressed and uncompressed > archives concatenater together (and the compressor doesn't need to be > the same, either). > -- > Henrique Holschuh >
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