scdbac...@gmx.net, debian-user@lists.debian.org Thomas, Thank you for your previous assistance concerning the hacked iso issue. Below is my progress. The only remaining issues are found in Retort4-5 below:
<Quote1> Why this overwriting of partition 1 by zeros ? The partition table will be overwritten by the ISO anyways. Retort1-->Thanks for this info. -------------------------------------------- <Quote2> dd if=/media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-lxde-CD-1.iso of=/dev/sdb bs=1M ... (For me it runs substantially faster if i add option bs=1M.) Retort2-->I ran dd again: [code] $ dd if=/media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-lxde-CD-1.iso of=/dev/sdb dd: failed to open ‘/dev/sdb’: Permission denied $ ll /dev/sdb brw-rw----. 1 root disk 8, 16 8月 14 19:45 /dev/sdb $ sudo chown a:adm /dev/sdb $ ll /dev/sdb brw-rw----. 1 a adm 8, 16 8月 14 19:45 /dev/sdb $ ll /dev/sdb brw-rw----. 1 a adm 8, 16 8月 14 19:45 /dev/sdb $ dd if=/media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-lxde-CD-1.iso of=/dev/sdb $ dd if=/media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-lxde-CD-1.iso of=/dev/sdb bs=1M 613+0 records in 613+0 records out 642777088 bytes (643 MB) copied, 105.551 s, 6.1 MB/s [/code] -------------------------------------------- <Quote3> Did the command last long enough to be credible ? Did it report 1255424+0 records in 1255424+0 records out Retort3--> Again, I burnt the iso to disk again (above and below): [code] $ dd if=/media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-lxde-CD-1.iso of=/dev/sdb bs=1M 613+0 records in 613+0 records out 642777088 bytes (643 MB) copied, 105.551 s, 6.1 MB/s [/code] -------------------------------------------- <Quote4> When you write: $ dd if=debian-8.4.0-amd64-netinst.iso bs=1 skip=32768 count=6 | od -c ... 0000000 001 C D 0 0 1 Your file yielded two blanks on this shell command dd if="/dev/sdb" bs=2048 skip=16 count=1 | dd bs=1 count=6 | od -x | head -1 | \ awk '{print $2 " " $3 " " $4}' Wheras an ISO is supposed to yield (on little-endian machine): 4301 3044 3130 Retort4--> Do you mean that you want me to try out these commands? Or is the program not usable on an average lubuntu 14.04 Samsung netbook like mine? Is there anything more I can do? -------------------------------------------- <Quote5> As we learn from the copy-to-stick command, we need to curb to 1255424 blocks of dd''s default size (512 bytes per block). My USB stick is at /dev/sdc: $ dd if=/dev/sdc count=1255424 | sha256sum Retort5--> May I assume that the number "1255424" is the records in/out integer? The first results below I used a count matching the burn of the iso to sdb: [code] $ dd if=/dev/sdb count=613 | sha256sum 613+0 records in 613+0 records out 313856 bytes (314 kB) copied, 0.0509401 s, 6.2 MB/s 943ad23096494bdff9a29f99368430285f8ecbe57da49db3d1fcf4be0800643d - [/code] The second results below I used a count matching the burn of the iso to sdb: [code] $ dd if=/dev/sdb count=1255424 | sha256sum 1255424+0 records in 1255424+0 records out fd7729e3bdfcb2b1b8793f5a19096fb2eee3cf709c39112ed2da7e7a2d7f6886 - 642777088 bytes (643 MB) copied, 31.813 s, 20.2 MB/s $ sha256sum /media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-lxde-CD-1.iso fd7729e3bdfcb2b1b8793f5a19096fb2eee3cf709c39112ed2da7e7a2d7f6886 [/code] Quite incredible, with the 'magic' number of "1255424" and using sha256sum the "/dev/sdb" and the original iso MATCH!!! But not the above command using the "records in/out integer" of 613(M), which is coincidentally the size of the downloaded iso on the local disk. Where does the number 1255424 come from? I notice that 613 M = 613 000 000 and if you break this down into 512 K than 613M / 512K = 1197265.6 which is near the magic number, is this not important? At this point I still didn't know where the 'magic number' came from. At this time I thought that sha256sum wasn't my target checksum, so I checked both /dev/sdb and the original iso with sha512sum: [code] $ dd if=/dev/sdb count=1255424 | sha512sum && wait && sha512sum /media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-lxde-CD-1.iso 1255424+0 records in 1255424+0 records out 642777088 bytes (643 MB) copied, 124.684 s, 5.2 MB/s 3365649694bf623d63f37853582d3fe0f7aa774821e2533d2dc79f5d763df1751e20da98da013ccc9bd3257159362434462bd7363caff3a590e75701b81e751c - 3365649694bf623d63f37853582d3fe0f7aa774821e2533d2dc79f5d763df1751e20da98da013ccc9bd3257159362434462bd7363caff3a590e75701b81e751c /media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-lxde-CD-1.iso [/code] It looks like the sha512sum of the /dev/sdb and the original iso MATCH ALSO!!! But may I understand the 'magic number' better? Sincerely, Andrew P.S. - Is there any forum (like linuxquestions.org) that I could post this on? I am new to debian and doubt the email thing is as quick as the email mailing list. -------- Original Message -------- Subject: Re: iso hacked suspicious: answers Local Time: August 10, 2016 5:23 PM UTC Time: August 10, 2016 5:23 PM From: scdbac...@gmx.net To: debian-user@lists.debian.org Hi, Andrew F Comly wrote: > E) Burn iso to media > dd if=/dev/zero of=/dev/sdb1 bs=1M; > wait; Why this overwriting of partition 1 by zeros ? The partition table will be overwritten by the ISO anyways. (And on what asynchronous processes are you waiting to end ?) > ddif=/media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-l xde-CD-1.iso of=/dev/sdb Blanks matter. :)) Assumed that you did put a blank between "dd" and "/media", the command would be ok for copying the ISO onto a USB stick at /dev/sdb. (For me it runs substantially faster if i add option bs=1M.) Did the command last long enough to be credible ? Did it report 1255424+0 records in 1255424+0 records out ? > sudo sha256sum /dev/sdb As we learn from the copy-to-stick command, we need to curb to 1255424 blocks of dd's default size (512 bytes per block). My USB stick is at /dev/sdc: $ dd if=/dev/sdc count=1255424 | sha256sum ... fd7729e3bdfcb2b1b8793f5a19096fb2eee3cf709c39112ed2da7e7a2d7f6886 - $ fgrep fd7729e3bdfcb2b1b8793f5a19096fb2eee3cf709c39112ed2da7e7a2d7f6886 SHA256SUMS fd7729e3bdfcb2b1b8793f5a19096fb2eee3cf709c39112ed2da7e7a2d7f6886 debian-8.5.0-i386-lxde-CD-1.iso Testing with ./check_debian_iso (which counts blocks of 2048 bytes each): $ ./check_debian_iso SHA512SUMS debian-8.5.0-i386-lxde-CD-1.iso /dev/sdc Piping 313856 blocks of '/dev/sdc' through 'sha256sum' to verify checksum list item 'debian-8.5.0-i386-lxde-CD-1.iso'. 313856+0 records in 313856+0 records out 642777088 bytes (643 MB) copied, 31.7854 s, 20.2 MB/s Ok: '/dev/sdc' matches 'debian-8.5.0-i386-lxde-CD-1.iso' in 'SHA256SUMS' Have a nice day :) Thomas