bash/sh incrementing for loop

  i=0; while [ $i -le 255 ]
 do
 echo evvdyn$i:nodhcp:10.11.16.$i::
 i=`expr $i + 1`
 done

Send a process to the background - "fork" - the command missing from Linux proper

These will send the process to the background and send a "wall" broadcast when complete.

$ cat fork
#!/usr/bin/bash
echo $*
(/usr/bin/nohup /usr/local/etc/fork2 $* > /tmp/nohup$$.txt &)&


$ cat fork2
#!/usr/bin/bash
/usr/bin/wall $* completed

Ping until failure - AND - Wait for a ping

These two Perl scripts fork to the background and call each other in turn to help track important systems.

 -------------------------- ping2failure --------------------

#!/usr/bin/perl

#

$MAIL_CMD = "/bin/mail";

$PING = "/bin/ping";

$dofork = 1;

$target = $ARGV[0];

die "No target.\n" if ($target eq "");

if ($dofork) {

if (open(PS, "/bin/ps ax | /bin/grep \"ping2failure $target\" | /bin/grep -v grep |")) {

    @psax = <PS>;

    close(PS);

    #print "@psax";

    for(@psax) {

        s/^\s+//g;

        #print $_;

        if (/ping2failure $target/) {

            #print "$_";

            ($pid, @stuff) = split(/\s+/);

            #print "$$ pid is $pid and $stuff[0]\n";

            if ($pid != $$) {

                die "$target already being waited on\n";

                 # no reason to run if already doing this

            }

        }

    }

}

# deal with stdin, stdout, stderr, control terminal, and put self

# in background

$TIOCNOTTY = 0x20007471;

close(stdin);

open(stdout, ">/dev/null");

open(stderr, ">/dev/null");

if (open(tty, "/dev/tty")) {

    ioctl(tty, $TIOCNOTTY, 0);

    close(tty);

}

if (fork) {

    exit 0;

}

}

$pings = 0;

$go = 1;

while ($go) {

        $xrand = system("/usr/bin/shuf -i 7-25 -n1");

        chomp($xrand);

        sleep($xrand);

        open(DOPING,"$PING -c 5 -W 45 $target |");

        @hello = <DOPING>;

        close(DOPING);

        for (@hello) {

                chomp;

                $x = $_;

                if ($x =~ /0 received/) {

                        open(DOPING,"$PING -c 5 -W 45 $target |");

                        @hello2 = <DOPING>;

                        close(DOPING);

                        for (@hello2) {

                                chomp;

                                $x = $_;

                                if ($x =~ /0 received/) {

                                        $go = 0;

                                        }

                                }

                        }

                }

        $pings++;

}

#system("/usr/bin/logger -p local1.emerg ping2failure $target is now off-line");

system("/usr/bin/logger -p local1.emerg ping2failure $target is now off-line ");

system("/usr/bin/wall ping2failure $target is now off-line ");

------------------ wait4ping ---------------------------

#!/usr/bin/perl

#

$MAIL_CMD = "/usr/bin/mail";

$PINGCMD = "/usr/bin/ping";

$target = $ARGV[0];

die "No target.\n" if ($target eq "");

if (open(PS, "/bin/ps ax | /bin/grep \"wait4ping $target\" | /bin/grep -v grep |")) {

    @psax = <PS>;

    close(PS);

    #print "@psax";

    for(@psax) {

        s/^\s+//g;

        #print $_;

        if (/wait4ping $target/) {

            #print "$_";

            ($pid, @stuff) = split(/\s+/);

            #print "$$ pid is $pid and $stuff[0]\n";

            if ($pid != $$) {

                die "$target already being waited on\n";

                 # no reason to run if already doing this

            }

        }

    }

}

# deal with stdin, stdout, stderr, control terminal, and put self

# in background

$TIOCNOTTY = 0x20007471;

close(stdin);

open(stdout, ">/dev/null");

open(stderr, ">/dev/null");

if (open(tty, "/dev/tty")) {

    ioctl(tty, $TIOCNOTTY, 0);

    close(tty);

}

if (fork) {

    exit 0;

}

$pings = 0;

while (1) {

        open(DOPING,"$PINGCMD -c 1 -W 45 $target |");

        @hello = <DOPING>;

        close(DOPING);

        last if ($hello[4] =~ /\,\s+1\s+received\,/);

        $pings++;

        $xrand = system("/usr/bin/shuf -i 17-37 -n1");

        chomp($xrand);

        sleep($xrand);

}

#system("/usr/bin/logger -p local1.emerg wait4ping $target is now on-line");

system("/usr/bin/logger -p local1.emerg wait4ping $target is now on-line ");

system("/usr/bin/wall wait4ping $target is now on-line ");

Fedora (et al) linux - enable/disable or start/stop the graphical user interface

Enable
 /usr/bin/systemctl set-default graphical.target

Disable
/usr/bin/systemctl set-default multi-user.target

Start
/usr/bin/systemctl start graphical.target

Stop
/usr/bin/systemctl stop graphical.target

Enable USB-to-serial-to-USB direct able connection to you Fedora and many other Linux flavors

/usr /bin/systemctl restart getty\@ttyUSB0

The backslash makes sure the command line uses the @ sign literally.

Enable telnet on Fedora

dnf -y install telnet-server telnet
systemctl enable telnet.socket
systemctl start telnet.socket



- yes I don't care if it's not best practices. The occasional use of telnet is a nice fallback when things get sideways.

Use all the space of a Micro-SD card of a Raspberry Pi running Fedora 34 (or possibly higher)

 To expand the root partition

growpart /dev/mmcblk0 3
pvresize /dev/mmcblk0p3
lvextend -r -l +100%FREE  /dev/mapper/fedora_fedora-root
xfs_growfs -d /