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Re: How to restore BIOS-based backup on a UEFI machine

Jesper Dybdal writes:


On 2021-01-14 23:21, Linux-Fan wrote:
Finally out of curiosity: You mention using CPIO archives. Do you have any input files above 8 GiB for your backup processes? I always thought that to be the limit of CPIO?
My backups do not contain large files within the cpio archives, so I don't know whether that would be a problem.  But some of the archives are much larger than 8 GiB. 

Thank you for confirming this.
I've just realized that I may never actually have restored such large backups, but I have created contents listings for them, and if cpio can do that, surely it can also restore (but I'll try a real restore just to be sure).
As long as the individual files are below 8 GiB (in your case: 4 GiB), it should be fine. See below.
Since cpio as I use it works from and to standard input/output, I would not expect it to notice the archive size in any way.
Yes, that is what I think too. The 8 GiB are only a restriction of the individual input files, not for the resulting archive files. Here is the except from GNU CPIOs manpage cpio(1): 

| -H, --format=FORMAT
|        Use given archive FORMAT.  Valid  formats  are  (the  number  in
|        parentheses gives maximum size for individual archive member):
|
|        bin    The obsolete binary format.  (2147483647 bytes)
|
|        odc    The old (POSIX.1) portable format. (8589934591 bytes)
|
|        newc   The  new (SVR4) portable format, which supports file sys‐
|               tems having more than 65536 i-nodes. (4294967295 bytes)
|
|        crc    The new (SVR4) portable format with a checksum added.
|
|        tar    The old tar format. (8589934591 bytes)
|
|        ustar  The POSIX.1 tar format.   Also  recognizes  GNU  tar  ar‐
|               chives,  which are similar but not identical. (8589934591
|               bytes)
|
|        hpbin  The obsolete binary format used  by  HPUX's  cpio  (which
|               stores device files differently).
|
|        hpodc  The portable format used by HPUX's cpio (which stores de‐
|               vice files differently).


I back up with
  cd / && find home -xdev -print0 | cpio -o0 -H crc | gzip | openssl enc -md sha256 -salt -pass file:passwordfile -aes-128-cbc >backup.cpio.gz.aes
Hence in your case, the limit should be effectively max. 4 GiB per input file. As it is a streamed format, there is no practical limit on the resulting output archive file. Thank you for the `openssl` commandline. 

Linux-Fan

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