(to be sorted later)

xenethernetnetwork

• https://wiki.xenproject.org/wiki/Xen_Networking#MAC_addresses
• https://en.wikipedia.org/wiki/MAC_address#Universal_addresses_that_are_administered_locally

I conclude, that software generated MAC addresses in the Xen context need to start with

00:16:3e:xx:xx:xx

printf '00:16:3e:%02x:%02x:%02x\n' $((RANDOM%256)) $((RANDOM%256)) $((RANDOM%256))
ip link set $IFACE address $HWADDR

or¹⁾

x2-xx-xx-xx-xx-xx
x6-xx-xx-xx-xx-xx
xa-xx-xx-xx-xx-xx
xe-xx-xx-xx-xx-xx

printf '%02x:%02x:%02x:%02x:%02x:%02x\n' $(( (RANDOM%256 | 0x02) & 0xfe )) $((RANDOM%256)) $((RANDOM%256)) $((RANDOM%256)) $((RANDOM%256)) $((RANDOM%256))
ip link set $IFACE address $HWADDR

ssh

ssh-keygen -lf <pub key file>

The part to be entered at the ssh prompt when connecting to unknown hosts is after the number, i.e. starting with the alg. specifier and need not contain the comment.

screenlessipfire

~/.screenrc

# workaround for the glitch, that "less" inside "screen" 5 on 
# "ipfire" 2.29 shows blinking text instead of reverse video:
setenv LESS_TERMCAP_so ^[[7m
setenv LESS_TERMCAP_se ^[[27m
:
:

Credits: ChatGPT

nagiosicingabash

$ needs to be escaped by a second $$

/etc/icinga/commands.cfg

   command_line /usr/local/bin/send_something.sh "$$(printf '%s\n%s' '$HOSTNAME' '$HOSTOUTPUT')"

Credits: Nagios Object Definitions at old-www-mathrice.pages.math.cnrs.fr (Well actually that was the first relevant Startpage hit after ChatGPT failed completely)
Reference: Command Definition - The primary source of the above

ntfypam

/etc/pam.d/common-session

:
session default=ignore pam_exec.so quiet /bin/sh -c [ test 'open_session' = "$PAM_TYPE" && /usr/bin/wget -q -O /dev/null --post-data "$PAM_USER hat sich gerade von $PAM_RHOST über $PAM_TTY eingeloggt" --header "X-Title: Login" --header "X-Priority: 4" --header "X-Tags: unlock" https://ntfy.sh/my_ntfy_topic]

$PAM_TTY will be ssh when appropriate

References:

• man 5 pam.conf
• man 8 pam_exec

lsofnetwork

lsof -iUDP:5353
lsof -iTCP:22

shellbashrcs

for i in `seq 1 17`
do
  rlog -r1.2.1.$i /etc/RCS/fstab,v > /tmp/work/log/1.2.1.$i
  co -u -M -r1.2.1.$i /etc/RCS/fstab,v
  log=$( ( egrep -m1 '^date: .*author:.*state:' ; sed '$d' | fgrep -v '*** empty log message ***' ) < /tmp/work/log/1.2.1.$i | sed '1d' )
  rcs -l1 /etc/RCS/fstab,v
  ci -d -m"$log" /etc/RCS/fstab,v
done

diff  <(rlog -r1 /etc/RCS/fstab,v )  <(rlog -r1.2.1 /etc/RCS/fstab,v )

for i in `seq 17 -1 1`
do
  j=$(( i+2 ))
  rcsdiff -r1.2.1.$i -r1.$j /etc/RCS/fstab,v \
  && rcs -o1.2.1.$i /etc/RCS/fstab,v
done

bash

shopt -s lithist

zsh

setopt shwordsplit

shelllessdiff

apt install --no-install-recommends source-highlight colordiff ccze
export LESSOPEN="| /usr/share/source-highlight/src-hilite-lesspipe.sh %s"
export LESS="-R"
less  index.php
rcsdiff index.php | colordiff | less -SRF
rlog index.php | ccze -A | less -SRF

~ # dmidecode -s system-serial-number                      

linuxUSBudev

udevadm trigger
# ? # udevadm trigger --action=add 
echo 1 > /sys/class/block/sd[x]/device/delete