DHCP debugging with tcpdump

tcpdump filter to match DHCP packets including a specific Client MAC Address: tcpdump -i br0 -vvv -s 1500 ‘((port 67 or port 68) and (udp[38:4] = 0x3e0ccf08))’ tcpdump filter to capture packets sent by the client (DISCOVER, REQUEST, INFORM): tcpdump -i br0 -vvv -s 1500 ‘((port 67 or port 68) and (udp[8:1] = 0x1))’ Sample…

Convert Large numbers to binary in Excel

=DEC2BIN(MOD(QUOTIENT($A$1,16^7),16),4)&” “&DEC2BIN(MOD(QUOTIENT($A$1,16^6),16),4)&” “&DEC2BIN(MOD(QUOTIENT($A$1,16^5),16),4)&” “&DEC2BIN(MOD(QUOTIENT($A$1,16^4),16),4)&” “&DEC2BIN(MOD(QUOTIENT($A$1,16^3),16),4)&” “&DEC2BIN(MOD(QUOTIENT($A$1,16^2),16),4)&” “&DEC2BIN(MOD(QUOTIENT($A$1,16^1),16),4)&” “&DEC2BIN(MOD(QUOTIENT($A$1,16^0),16),4) The above code will convert large numbers up to 32 bit. nJoy 😉

Get ssh key fingerprint for comparing safely

SSh keys can be long and unwieldy to compare. Many platforms digest them to md5 formats for non disclosure such as github. This command will give you the digested fingerprint of an ssh key in linux / Mac. nJoy 😉

Get Days in a month from a bash script

Useful listing of days in a month to populate directories or run scripts for backing up getting the correct dates of days in a month and year.     YEAR=2020 MONTH=2 for DAY in $(DAYS=`cal $MONTH $YEAR | awk ‘NF {DAYS = $NF}; END {print DAYS}’` && seq -f ‘%02G’ $DAYS) ;do DATE=”$YEAR-$MONTH-$DAY” echo $DATE…

SYSTEMD – controls

Starting with Ubuntu 15.04, Upstart will be deprecated in favor of Systemd. With Systemd to manage the services we can do the following: systemctl start SERVICE – Use it to start a service. Does not persist after reboot systemctl stop SERVICE – Use it to stop a service. Does not persist after reboot systemctl restart…

Automatically passing ssh password in scripts especially to ESX where passwordless ssh is hard

First you need to install sshpass. Ubuntu/Debian: apt-get install sshpass Fedora/CentOS: yum install sshpass Arch: pacman -S sshpass Example: sshpass -p “YOUR_PASSWORD” ssh -o StrictHostKeyChecking=no YOUR_USERNAME@SOME_SITE.COM Custom port example: sshpass -p “YOUR_PASSWORD” ssh -o StrictHostKeyChecking=no YOUR_USERNAME@SOME_SITE.COM:2400 from : https://stackoverflow.com/questions/12202587/automatically-enter-ssh-password-with-script   This works better for me though for sshfs: echo $mypassword | sshfs -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no user@host mountpoint -o workaround=rename…

fail to mount ntfs in BSD

[root@ftp /mnt/test]# ntfs-3g /dev/da10s1 /mnt/test fuse: failed to open fuse device: No such file or directory kldload fuse That’s a missing module needs loading. nJoy 😉