GNU coreutils: Sources of random data

script file contents

#!/bin/bash

get_seeded_random()
{
    seed="$1"
    echo $seed
    openssl enc -aes-256-ctr -pass pass:"$seed" -nosalt \
	    /dev/null
}

shuf -i1-100 --random-source=<(get_seeded_random 45)

using /dev/urandom 

$sudo shuf -i1-5 --random-source=/dev/urandom
1
2
4
3
5
$sudo shuf -i1-5 --random-source=/dev/urandom
3
4
5
1
2
$sudo shuf -i1-5 --random-source=/dev/urandom
4
5
2
1
3
$sudo shuf -i1-5 --random-source=/dev/urandom
4
2
3
1
5
$sudo shuf  --random-source=/dev/urandom
^C
$sudo shuf -i1-10 --random-source=/dev/urandom
2
4
6
10
7
8
5
3
1
9
$sudo shuf -i1-10 --random-source=/dev/urandom
6
2
10
3
5
8
7
9
4
1
$sudo shuf -i1-10 
5
4
10
8
9
6
7
1
2
3
$sudo shuf 
qq


qq
$sudo shuf -i1-100 --random-source=/dev/urandom
65
51
62
79
41
35
26
36
52
77
54
82
48
99
75
17
39
31
1
7
88
61
9
94
73
70
63
55
44
38
23
84
15
25
53
85
66
16
20
69
81
32
98
45
96
49
74
10
4
59
93
40
12
13
50
100
14
90
6
68
8
57
5
34
60
67
80
3
2
78
18
76
21
92
33
56
24
37
87
83
47
29
97
46
89
43
91
27
11
58
64
19
28
86
95
72
30
22
71
42
$sudo shuf -i1-100 --random-source=/dev/random
8
79
40
19
62
27
90
71
9
93
32
85
21
3
26
31
63
18
99
2
78
11
100
49
75
64
37
13
39
30
29
73
82
34
55
14
35
80
84
33
67
98
92
25
87
51
41
88
10
4
97
45
53
68
16
15
47
46
42
36
54
94
70
28
61
83
58
96
69
91
59
1
72
38
5
23
60
12
74
44
7
52
48
86
43
95
20
65
50
24
76
22
6
66
81
89
56
77
17
57
$sudo shuf -i1-100 --random-source=/dev/null
shuf: ‘/dev/null’: end of file
$sudo shuf -i1-100 --random-source=/dev/zero
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
$

What if a user or group name is a string of digits?

root>useradd 1991
root>mkdir /home/1991
root>chown 1991.1991 /home/1991/
root>passwd 1991
Enter new UNIX password: 
Retype new UNIX password: 
passwd: password updated successfully
root>login 1991
Password: 

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
$ 
root>deluser 1991
Removing user `1991' ...
Warning: group `1991' has no more members.
Done.
root>


root>ls
Desktop
root>cd /home/
root>ls
1991  jeffrin
root>rm -r 1991/
root>cd
root>



root>useradd 471
root>mkdir /home/471
root>chown 471.471  /home/471/
root>ls -l /home/
total 8
drwxr-xr-x  2 471     471     4096 Apr 15 17:57 471
drwxr-xr-x 24 jeffrin jeffrin 4096 Apr 15 17:25 jeffrin
root>chown +471:+471 /home/471/
root>ls -l /home/
total 8
drwxr-xr-x  2     471     471 4096 Apr 15 17:57 471
drwxr-xr-x 24 jeffrin jeffrin 4096 Apr 15 17:25 jeffrin
root>chown +471 /home/471/
root>ls -l /home/
total 8
drwxr-xr-x  2     471     471 4096 Apr 15 17:57 471
drwxr-xr-x 24 jeffrin jeffrin 4096 Apr 15 17:25 jeffrin
root>

https://www.gnu.org/software/coreutils/manual/coreutils.html#Disambiguating-names-and-IDs

GNU coreutils: signal specifications . commands “kill” and “nohup”

$kill -l
 1) SIGHUP	 2) SIGINT	 3) SIGQUIT	 4) SIGILL	 5) SIGTRAP
 6) SIGABRT	 7) SIGBUS	 8) SIGFPE	 9) SIGKILL	10) SIGUSR1
11) SIGSEGV	12) SIGUSR2	13) SIGPIPE	14) SIGALRM	15) SIGTERM
16) SIGSTKFLT	17) SIGCHLD	18) SIGCONT	19) SIGSTOP	20) SIGTSTP
21) SIGTTIN	22) SIGTTOU	23) SIGURG	24) SIGXCPU	25) SIGXFSZ
26) SIGVTALRM	27) SIGPROF	28) SIGWINCH	29) SIGIO	30) SIGPWR
31) SIGSYS	34) SIGRTMIN	35) SIGRTMIN+1	36) SIGRTMIN+2	37) SIGRTMIN+3
38) SIGRTMIN+4	39) SIGRTMIN+5	40) SIGRTMIN+6	41) SIGRTMIN+7	42) SIGRTMIN+8
43) SIGRTMIN+9	44) SIGRTMIN+10	45) SIGRTMIN+11	46) SIGRTMIN+12	47) SIGRTMIN+13
48) SIGRTMIN+14	49) SIGRTMIN+15	50) SIGRTMAX-14	51) SIGRTMAX-13	52) SIGRTMAX-12
53) SIGRTMAX-11	54) SIGRTMAX-10	55) SIGRTMAX-9	56) SIGRTMAX-8	57) SIGRTMAX-7
58) SIGRTMAX-6	59) SIGRTMAX-5	60) SIGRTMAX-4	61) SIGRTMAX-3	62) SIGRTMAX-2
63) SIGRTMAX-1	64) SIGRTMAX	
$kill -19 `pidof chromium-browse`
$kill -18 `pidof chromium-browse`
$kill -5 `pidof chromium-browse`
$kill -1 `pidof chromium-browse`
$nohup chromium-browser 
nohup: ignoring input and appending output to 'nohup.out'

$
$nohup chromium-browser 
nohup: ignoring input and appending output to 'nohup.out'

$
$kill -1 `pidof chromium-browse`
kill: usage: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ... or kill -l [sigspec]
$kill -3 `pidof chromium-browse`
kill: usage: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ... or kill -l [sigspec]
$nohup chromium-browser 
nohup: ignoring input and appending output to 'nohup.out'



$
$
$
$echo $?
0
$

GNU coreutils: block size related to df command

ABOUT df

df (abbreviation for disk free) is a standard Unix command used to display the amount of
available disk space for file systems on which the invoking user has appropriate read access.
df is typically implemented using the statfs or statvfs system calls.

[bash]
$df
Filesystem 1K-blocks Used Available Use% Mounted on
udev 1921644 0 1921644 0% /dev
tmpfs 388676 6508 382168 2% /run
/dev/sda2 475184136 6024592 444951776 2% /
tmpfs 1943372 1460 1941912 1% /dev/shm
tmpfs 5120 4 5116 1% /run/lock
tmpfs 1943372 0 1943372 0% /sys/fs/cgroup
/dev/sda1 523248 3660 519588 1% /boot/efi
tmpfs
[/bash] 388672 104 388568 1% /run/user/1000

[bash]
$df -h
Filesystem Size Used Avail Use% Mounted on
udev 1.9G 0 1.9G 0% /dev
tmpfs 380M 6.4M 374M 2% /run
/dev/sda2 454G 5.8G 425G 2% /
tmpfs 1.9G 1.5M 1.9G 1% /dev/shm
tmpfs 5.0M 4.0K 5.0M 1% /run/lock
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sda1 511M 3.6M 508M 1% /boot/efi
tmpfs 380M 104K 380M 1% /run/user/1000
$export DF_BLOCK_SIZE=2k
[/bash]

[bash]
$df
Filesystem 2K-blocks Used Available Use% Mounted on
udev 960822 0 960822 0% /dev
tmpfs 194338 3254 191084 2% /run
/dev/sda2 237592068 3012288 222475896 2% /
tmpfs 971686 136 971550 1% /dev/shm
tmpfs 2560 2 2558 1% /run/lock
tmpfs 971686 0 971686 0% /sys/fs/cgroup
/dev/sda1 261624 1830 259794 1% /boot/efi
tmpfs 194336 50 194286 1% /run/user/1000
$export POSIXLY_CORRECT=1
[/bash]

[bash]
$df
Filesystem 2K-blocks Used Available Use% Mounted on
udev 960822 0 960822 0% /dev
tmpfs 194338 3252 191086 2% /run
/dev/sda2 237592068 3018782 222469402 2% /
tmpfs 971686 618 971068 1% /dev/shm
tmpfs 2560 2 2558 1% /run/lock
tmpfs 971686 0 971686 0% /sys/fs/cgroup
/dev/sda1 261624 1830 259794 1% /boot/efi
tmpfs 194336 46 194290 1% /run/user/1000
$set -o posix
[/bash]

[bash]
$df
Filesystem 2K-blocks Used Available Use% Mounted on
udev 960822 0 960822 0% /dev
tmpfs 194338 3252 191086 2% /run
/dev/sda2 237592068 3018774 222469410 2% /
tmpfs 971686 618 971068 1% /dev/shm
tmpfs 2560 2 2558 1% /run/lock
tmpfs 971686 0 971686 0% /sys/fs/cgroup
/dev/sda1 261624 1830 259794 1% /boot/efi
tmpfs 194336 46 194290 1% /run/user/1000
$
[/bash]

https://en.wikipedia.org/wiki/Df_(Unix)
https://www.gnu.org/software/coreutils/manual/coreutils.html#df-invocation