Unix & Linux Asked by x6herbius on October 31, 2021
Perhaps I’m doing something very stupid here, but Google hasn’t been very helpful in resolving the problem.
I have an archive of files I made for backup purposes. I’ve generated an SHA1 checksum file from this archive:
sha1sum myarchive.tar > myarchive.tar.sha1
The contents of this file are as follows:
6f5d7bdd71fe25ed8e881265fdb8a8bbcdaa41c1 myarchive.tar
I have also run the SHA1 process in the terminal without piping to a file:
sha1sum myarchive.tar
This gives me the output:
6f5d7bdd71fe25ed8e881265fdb8a8bbcdaa41c1 myarchive.tar
Clearly these checksums are the same. However, when I run the verification command, with the archive and its SHA1 file next to each other in the same directory:
sha1sum -c myarchive.tar.sha1
I get an error message saying that the checksum does not match:
myarchive.tar: FAILED
sha1sum: WARNING: 1 computed checksum did NOT match
Obviously something is wrong here, but I have no idea what it could be. Can anyone enlighten me?
EDIT: Interestingly, doing two consecutive MD5s on the file comes up with two different checksums. Now I’m very confused.
$ md5sum myarchive.tar
9a15036eed341613bbcf2c4b53a09859 myarchive.tar
$ md5sum myarchive.tar
a662d6b469627c62f2b03ee0df067436 myarchive.tar
EDIT2: Additional context:
EDIT3: In response to requests to see the output of dmesg, there appear to be a few errors like the following:
[ 7102.039819] perf: interrupt took too long (2502 > 2500), lowering kernel.perf_event_max_sample_rate to 79750
[ 8278.017874] sr 4:0:0:0: [sr0] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 8278.017876] sr 4:0:0:0: [sr0] tag#0 Sense Key : Blank Check [current]
[ 8278.017877] sr 4:0:0:0: [sr0] tag#0 Add. Sense: No additional sense information
[ 8278.017878] sr 4:0:0:0: [sr0] tag#0 CDB: Read(10) 28 00 00 00 00 00 00 00 01 00
[ 8278.017879] blk_update_request: critical target error, dev sr0, sector 0 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 0
[ 8278.019391] sr 4:0:0:0: [sr0] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 8278.019392] sr 4:0:0:0: [sr0] tag#0 Sense Key : Blank Check [current]
[ 8278.019392] sr 4:0:0:0: [sr0] tag#0 Add. Sense: No additional sense information
[ 8278.019393] sr 4:0:0:0: [sr0] tag#0 CDB: Read(10) 28 00 00 00 00 00 00 00 01 00
[ 8278.019394] blk_update_request: critical target error, dev sr0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
[ 8278.019396] Buffer I/O error on dev sr0, logical block 0, async page read
I think this is to do with my USB Blu Ray drive, though someone may be able to correct me.
There are 2 things that need some scrupulous investigation in your case.
As proven with your dmesg output snippet, your Blu-Ray disc has reached end-of-life. There is no way to fix that disc, unless the Blu-Ray drive manages to read the data on the Blu-Ray disc 100% fine, which is improbable at this point.
Personal recommendation regarding Blu-Ray discs: If ever I have to use for whatever reason my Blu-Ray Drive to burn something, I sure use the M-Disc (wiki) Blu-Ray discs. For highly sensitive small data it's close to perfect storage.
The varying consecutive checksum read from your computer storage would bother me more, if that was read from your storage, that is. You could in theory have bad RAM, but that is not much probable. My advice is to watch the output of dmesg (man page) for a long period of time, example of such command follows:
dmesg --human --color=auto --ctime --level=err,warn --follow
That could help you identify if your storage, be it a classic SATA HDD, or modern M.2 NVMe SSD, it does not matter, is failing. If you find there actually is a problem with your storage, better have backups prepared.
I hope this answer helps someone in similar position.
Answered by LinuxSecurityFreak on October 31, 2021
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