Ciro Santilli @cirosantilli 35

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Twin prime  Updated 2025-04-24  +Created 1970-01-01

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Domain (biology)  Updated 2025-04-24  +Created 1970-01-01

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ELF Hello World Tutorial / Executable hd  Updated 2025-04-24  +Created 1970-01-01

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Running:

hd hello_world.out

gives:

00000000  7f 45 4c 46 02 01 01 00  00 00 00 00 00 00 00 00  |.ELF............|
00000010  02 00 3e 00 01 00 00 00  b0 00 40 00 00 00 00 00  |..>.......@.....|
00000020  40 00 00 00 00 00 00 00  10 01 00 00 00 00 00 00  |@...............|
00000030  00 00 00 00 40 00 38 00  02 00 40 00 06 00 03 00  |....@.8...@.....|
00000040  01 00 00 00 05 00 00 00  00 00 00 00 00 00 00 00  |................|
00000050  00 00 40 00 00 00 00 00  00 00 40 00 00 00 00 00  |..@.......@.....|
00000060  d7 00 00 00 00 00 00 00  d7 00 00 00 00 00 00 00  |................|
00000070  00 00 20 00 00 00 00 00  01 00 00 00 06 00 00 00  |.. .............|
00000080  d8 00 00 00 00 00 00 00  d8 00 60 00 00 00 00 00  |..........`.....|
00000090  d8 00 60 00 00 00 00 00  0d 00 00 00 00 00 00 00  |..`.............|
000000a0  0d 00 00 00 00 00 00 00  00 00 20 00 00 00 00 00  |.......... .....|
000000b0  b8 01 00 00 00 bf 01 00  00 00 48 be d8 00 60 00  |..........H...`.|
000000c0  00 00 00 00 ba 0d 00 00  00 0f 05 b8 3c 00 00 00  |............<...|
000000d0  bf 00 00 00 00 0f 05 00  48 65 6c 6c 6f 20 77 6f  |........Hello wo|
000000e0  72 6c 64 21 0a 00 2e 73  79 6d 74 61 62 00 2e 73  |rld!...symtab..s|
000000f0  74 72 74 61 62 00 2e 73  68 73 74 72 74 61 62 00  |trtab..shstrtab.|
00000100  2e 74 65 78 74 00 2e 64  61 74 61 00 00 00 00 00  |.text..data.....|
00000110  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000150  1b 00 00 00 01 00 00 00  06 00 00 00 00 00 00 00  |................|
00000160  b0 00 40 00 00 00 00 00  b0 00 00 00 00 00 00 00  |..@.............|
00000170  27 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |'...............|
00000180  10 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000190  21 00 00 00 01 00 00 00  03 00 00 00 00 00 00 00  |!...............|
000001a0  d8 00 60 00 00 00 00 00  d8 00 00 00 00 00 00 00  |..`.............|
000001b0  0d 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001c0  04 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001d0  11 00 00 00 03 00 00 00  00 00 00 00 00 00 00 00  |................|
000001e0  00 00 00 00 00 00 00 00  e5 00 00 00 00 00 00 00  |................|
000001f0  27 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |'...............|
00000200  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000210  01 00 00 00 02 00 00 00  00 00 00 00 00 00 00 00  |................|
00000220  00 00 00 00 00 00 00 00  90 02 00 00 00 00 00 00  |................|
00000230  08 01 00 00 00 00 00 00  05 00 00 00 07 00 00 00  |................|
00000240  08 00 00 00 00 00 00 00  18 00 00 00 00 00 00 00  |................|
00000250  09 00 00 00 03 00 00 00  00 00 00 00 00 00 00 00  |................|
00000260  00 00 00 00 00 00 00 00  98 03 00 00 00 00 00 00  |................|
00000270  4c 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |L...............|
00000280  01 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000290  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000002a0  00 00 00 00 00 00 00 00  00 00 00 00 03 00 01 00  |................|
000002b0  b0 00 40 00 00 00 00 00  00 00 00 00 00 00 00 00  |..@.............|
000002c0  00 00 00 00 03 00 02 00  d8 00 60 00 00 00 00 00  |..........`.....|
000002d0  00 00 00 00 00 00 00 00  01 00 00 00 04 00 f1 ff  |................|
000002e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000002f0  11 00 00 00 00 00 02 00  d8 00 60 00 00 00 00 00  |..........`.....|
00000300  00 00 00 00 00 00 00 00  1d 00 00 00 00 00 f1 ff  |................|
00000310  0d 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000320  00 00 00 00 04 00 f1 ff  00 00 00 00 00 00 00 00  |................|
00000330  00 00 00 00 00 00 00 00  2d 00 00 00 10 00 01 00  |........-.......|
00000340  b0 00 40 00 00 00 00 00  00 00 00 00 00 00 00 00  |..@.............|
00000350  34 00 00 00 10 00 02 00  e5 00 60 00 00 00 00 00  |4.........`.....|
00000360  00 00 00 00 00 00 00 00  40 00 00 00 10 00 02 00  |........@.......|
00000370  e5 00 60 00 00 00 00 00  00 00 00 00 00 00 00 00  |..`.............|
00000380  47 00 00 00 10 00 02 00  e8 00 60 00 00 00 00 00  |G.........`.....|
00000390  00 00 00 00 00 00 00 00  00 68 65 6c 6c 6f 5f 77  |.........hello_w|
000003a0  6f 72 6c 64 2e 61 73 6d  00 68 65 6c 6c 6f 5f 77  |orld.asm.hello_w|
000003b0  6f 72 6c 64 00 68 65 6c  6c 6f 5f 77 6f 72 6c 64  |orld.hello_world|
000003c0  5f 6c 65 6e 00 5f 73 74  61 72 74 00 5f 5f 62 73  |_len._start.__bs|
000003d0  73 5f 73 74 61 72 74 00  5f 65 64 61 74 61 00 5f  |s_start._edata._|
000003e0  65 6e 64 00                                       |end.|
000003e4

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Endurance athlete  Updated 2025-04-24  +Created 1970-01-01

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How to teach / Projects with global impact  Updated 2025-04-24  +Created 1970-01-01

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Important Lie group  Updated 2025-04-24  +Created 1970-01-01

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Phase shift gate  Updated 2025-04-24  +Created 1970-01-01

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Project Xanadu  Updated 2025-04-24  +Created 1970-01-01

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Crazy overlaps with Ciro Santilli's OurBigBook Project, Wikipedia states:

Administrators of Project Xanadu have declared it superior to the World Wide Web, with the mission statement: "Today's popular software simulates paper. The World Wide Web (another imitation of paper) trivialises our original hypertext model with one-way ever-breaking links and no management of version or contents.

Video 1.

New Game in Town by TheTedNelson (2016)

Source.

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Webots  Updated 2025-04-24  +Created 1970-01-01

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github.com/cyberbotics/webots

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Domain, codomain and image  Updated 2025-04-24  +Created 1970-01-01

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Kardashev scale  Updated 2025-04-24  +Created 1970-01-01

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Kronecker delta  Updated 2025-04-24  +Created 1970-01-01

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Stefan Thomas  Updated 2025-04-24  +Created 1970-01-01

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www.nytimes.com/2021/01/12/technology/bitcoin-passwords-wallets-fortunes.html

As for his lost password and inaccessible Bitcoin, Mr. Thomas has put the IronKey in a secure facility - he won’t say where - in case cryptographers come up with new ways of cracking complex passwords. Keeping it far away helps him try not to think about it, he said.

“I would just lay in bed and think about it," Mr. Thomas said.

Video 1.

What is Bitcoin? (v1) by WeUseCoins (2011)

Source. This is the video that Stefan Thomas as paid 7,002 Bitcoins to make back in 2011.

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Ciro Santilli's hardware / Lenovo ThinkPad P51 (2017) log  Updated 2025-04-24  +Created 1970-01-01

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cirosantilli.com/linux-kernel-module-cheat/#p51 (permalink)

battery life:
- 2023-04: on-browser streaming + light browsing on Ubuntu 22.10: about 2h45. Too low! Gotta try buying a new battery.
2022-01-04 updated firmward after noticing that ubuntu 21.10 does not wake up from suspend seemed to happen every time when not connected to external power. dmidecode diff excerpt:
```
 BIOS Information
        Vendor: LENOVO
-       Version: N1UET40W (1.14 )
-       Release Date: 09/28/2017
+       Version: N1UET71W (1.45 )
+       Release Date: 07/18/2018
```
used the "Ubuntu Software" GUI as mentioned at: support.lenovo.com/gb/en/solutions/ht510810-how-to-do-software-updates-linux. Kudos for making this accessible to newbs.
After doing that, another update became available to: 0.1.56, clicked it and was much faster than the previous one, and didn't auto reboot. After manual reboot, dmidecode diffed again:
```
 BIOS Information
        Vendor: LENOVO
-       Version: N1UET71W (1.45 )
-       Release Date: 07/18/2018
+       Version: N1UET82W (1.56 )
+       Release Date: 08/12/2021
```
plus a bunch of other lines.

2021-06-05 upgraded to Ubuntu 21.04 with a clean install from an ISO. Selected

"Minimal installation"
"Erase disk and install Ubuntu". Notably, this erased the Microsoft Windows that came with the computer and was never used not even once
"Erase disk ans use ZFS"
Encrypt the new Ubuntu installation for security

After this, the GUI felt fast, who would have thought that erasing a bunch of stuff would make the system faster!

lsblk contains:

zd0               230:0    0   500M  0 disk
└─keystore-rpool  253:0    0   484M  0 crypt /run/keystore/rpool
nvme0n1           259:0    0 476.9G  0 disk
├─nvme0n1p1       259:1    0   512M  0 part  /boot/efi
├─nvme0n1p2       259:2    0     2G  0 part
│ └─cryptoswap    253:1    0     2G  0 crypt
├─nvme0n1p3       259:3    0     2G  0 part
└─nvme0n1p4       259:4    0 472.4G  0 part

and lsblk -f:

zd0               crypto_LUKS 2
└─keystore-rpool  ext4        1.0   keystore-rpool
nvme0n1
├─nvme0n1p1       vfat        FAT32
├─nvme0n1p2       crypto_LUKS 2
│ └─cryptoswap
├─nvme0n1p3       zfs_member  5000  bpool
└─nvme0n1p4       zfs_member  5000  rpoo

Then:

grep '[rb]pool' /proc/mounts

contains:

rpool/ROOT/ubuntu_uvs1fq / zfs rw,relatime,xattr,posixacl 0 0
rpool/USERDATA/ciro_czngbg /home/ciro zfs rw,relatime,xattr,posixacl 0 0
rpool/USERDATA/root_czngbg /root zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/srv /srv zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/usr/local /usr/local zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/games /var/games zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/log /var/log zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/lib /var/lib zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/mail /var/mail zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/snap /var/snap zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/www /var/www zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/spool /var/spool zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/lib/AccountsService /var/lib/AccountsService zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/lib/NetworkManager /var/lib/NetworkManager zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/lib/apt /var/lib/apt zfs rw,relatime,xattr,posixacl 0 0
rpool/ROOT/ubuntu_uvs1fq/var/lib/dpkg /var/lib/dpkg zfs rw,relatime,xattr,posixacl 0 0
bpool/BOOT/ubuntu_uvs1fq /boot zfs rw,nodev,relatime,xattr,posixacl 0 0

which gives an idea of how the above map to mountpoints.

Had two GUI freezes since installation, a fixed images shows no matter what I do, possibly graphics only, but impossible to tell (next time I'll try SSH access). No Nvidia drivers installed yet.

2020-06-06: dropped some lemon juice on the bottom left of touchpad. Bottom left button not working anymore... I'm an idiot. There are many other alternatives, but very aggravating, I'll replace it for sure. Can't find the exact replacement part or any videos showing its replacement online easliy, dang. For the T430: www.youtube.com/watch?v=F3lzV9uXRjU Asked at: forums.lenovo.com/t5/ThinkPad-P-and-W-Series-Mobile-Workstations/P51-left-bottom-button-below-trackpad-mouse-left-click-stopped-working-possible-to-replace/m-p/5019903 Also I could not access it because you need to remove the HDD first: www.youtube.com/watch?v=5Klawxc7T_Y and I can't pull it out even with considerable force, unlike in the video... And OMG, those button caps are impossible to re-install once removed!!! Then when I put the whole thing back together, the upper buttons were not working anymore. FUUUUUUUUCK. When first opening I pulled on it without properly removing the cap and it came off, but it didn't look broken in any way and I put it back in. Keyboard works thank God, so right black connector is fine, left white one oppears to be the one for upper keys and trackpoint, both of which stopped working. The hardware manual confirms that they are both part of the same device, so basically a mouse :-) TODO can it be bought separately from te keyboard? Doesn't look like it, photo of keyboard part includes those buttons. The manual also confirms that the bottom buttons are one device with the trackpad "trackpad with buttons", thus forming the second entire mouse.

2019-04-17: popup asking about "ThinkPad P51 Management Engine Update" from from 182.29.3287 to 184.60.3561, said yes.

Ubuntu 17.10 setup after buying it:

partition setup: askubuntu.com/questions/343268/how-to-use-manual-partitioning-during-installation/976430#976430
BIOS:
- for NVIDIA driver:
- for KVM, required by Android Emulator: enable virtualization extensions
TODO fix the brightness keys:
- failed: askubuntu.com/questions/769006/brightness-key-not-working-ubuntu-16-04-lts/770100#770100

Battery life shown by Ubuntu battery app after installation:

before NVIDIA driver setup: 8h
after: 6.5h

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Diameter  Updated 2025-04-24  +Created 1970-01-01

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ELF Hello World Tutorial / How to learn  Updated 2025-04-24  +Created 1970-01-01

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Spin like mad between:

standards
high level generators. We use the assembler as and linker ld.
hexdumps
file decompilers. We use readelf. It makes it faster to read the ELF file by turning it into human readable output. But you must have seen one byte-by-byte example first, and think how readelf output maps to the standard.
low-level generators: stand-alone libraries that let you control every field of the ELF files you generated. github.com/BR903/ELFkickers, github.com/sqall01/ZwoELF and many more on GitHub.
consumer: the exec system call of the Linux kernel can parse ELF files to starts processes: github.com/torvalds/linux/blob/v4.11/fs/binfmt_elf.c, stackoverflow.com/questions/8352535/how-does-kernel-get-an-executable-binary-file-running-under-linux/31394861#31394861

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ELF Hello World Tutorial / Section header table  Updated 2025-04-24  +Created 1970-01-01

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Array of Elf64_Shdr structs.

Each entry contains metadata about a given section.

e_shoff of the ELF header gives the starting position, 0x40 here.

e_shentsize and e_shnum from the ELF header say that we have 7 entries, each 0x40 bytes long.

So the table takes bytes from 0x40 to 0x40 + 7 + 0x40 - 1 = 0x1FF.

Some section names are reserved for certain section types: www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html#special_sections e.g. .text requires a SHT_PROGBITS type and SHF_ALLOC + SHF_EXECINSTR

Running:

readelf -S hello_world.o

outputs:

There are 7 section headers, starting at offset 0x40:

Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [ 0]                   NULL             0000000000000000  00000000
       0000000000000000  0000000000000000           0     0     0
  [ 1] .data             PROGBITS         0000000000000000  00000200
       000000000000000d  0000000000000000  WA       0     0     4
  [ 2] .text             PROGBITS         0000000000000000  00000210
       0000000000000027  0000000000000000  AX       0     0     16
  [ 3] .shstrtab         STRTAB           0000000000000000  00000240
       0000000000000032  0000000000000000           0     0     1
  [ 4] .symtab           SYMTAB           0000000000000000  00000280
       00000000000000a8  0000000000000018           5     6     4
  [ 5] .strtab           STRTAB           0000000000000000  00000330
       0000000000000034  0000000000000000           0     0     1
  [ 6] .rela.text        RELA             0000000000000000  00000370
       0000000000000018  0000000000000018           4     2     4
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

The struct represented by each entry is:

typedef struct {
    Elf64_Word  sh_name;
    Elf64_Word  sh_type;
    Elf64_Xword sh_flags;
    Elf64_Addr  sh_addr;
    Elf64_Off   sh_offset;
    Elf64_Xword sh_size;
    Elf64_Word  sh_link;
    Elf64_Word  sh_info;
    Elf64_Xword sh_addralign;
    Elf64_Xword sh_entsize;
} Elf64_Shdr;

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Mono  Updated 2025-04-24  +Created 1970-01-01

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One, single. Actual word: μόνος.

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The best science fiction works deeply explore the consequences of one single technology  Updated 2025-04-24  +Created 1970-01-01

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The impact of the work is greater when you examine what one single new technology would do to existing society, as in Primer (2004), rather than "start on a society with severl new technologies", like in Star Wars.

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Dictionary  Updated 2025-04-24  +Created 1970-01-01

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