Category: Howtos

How to quit ESXi SSH and leave background tasks running

Posted on by admin

In Linux when a console session is closed most background jobs (^Z and bg %n) will stop running when the parent ( the ssh session ) is closed because the parent sends a SIGHUP to all its children when closing (properly). Some programs can catch and ignore the SIGHUP or not handle it at all hence passing to the root init parent. The disown command in a shell removes a background job from the list to send SIGHUPs to.

In ESXi there is no disown command. However there is a way to close a shell immediately without issuing the SIGHUPs :

exec </dev/null >/dev/null 2>/dev/null

The exec command will run a command and switch it out for the current shell. Also this command will make sure the stdio and stderr are piped properly.

nJoy 😉

DHCP debugging with tcpdump

Posted on by admin

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 output :


 21:38:05.644153 IP (tos 0x0, ttl 64, id 32104, offset 0, flags [none], proto UDP (17), length 374)
     0.0.0.0.bootpc > 255.255.255.255.bootps: [udp sum ok] BOOTP/DHCP, Request from 12:42:82:cb:7a:7e (oui Unknown), length 346, xid 0xd01f0ad4, secs 18694, Flags [none] (0x0000)
   Client-Ethernet-Address 12:42:82:cb:7a:7e (oui Unknown)
   Vendor-rfc1048 Extensions
     Magic Cookie 0x63825363
     DHCP-Message Option 53, length 1: Discover
     Client-ID Option 61, length 7: ether 12:42:82:cb:7a:7e
     SLP-NA Option 80, length 0""
     NOAUTO Option 116, length 1: Y
     MSZ Option 57, length 2: 1472
     Vendor-Class Option 60, length 49: "dhcpcd-7.1.0:Linux-4.19.59-sunxi:armv7l:Allwinner"
     Hostname Option 12, length 11: "whiteorange"
     T145 Option 145, length 1: 1
     Parameter-Request Option 55, length 15: 
       Subnet-Mask, Classless-Static-Route, Static-Route, Default-Gateway
       Domain-Name-Server, Hostname, Domain-Name, MTU
       BR, NTP, Lease-Time, Server-ID
       RN, RB, Option 119
     END Option 255, length 0

…And yes it is an orangepi zero for those playing at home..

nJoy 😉

Get ssh key fingerprint for comparing safely

Posted on by admin

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.

ssh-keygen -lf .ssh/id_rsa.pub -E md5

nJoy 😉

Get Days in a month from a bash script

Posted on by admin

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
done

nJoy 😉

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

Posted on by admin

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 -o password_stdin

 

 

nJoy 😉

 

fail to mount ntfs in BSD

Posted on by admin 
[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 😉

Resizing a disk once the volume has grown on host in a VM (Ubuntu)

Posted on by admin

The disk will not automatically resize on many platforms once more disk space was made available.

Particularly in Ubuntu 16.04

Rescanning the device for size maps :

echo 1 > /sys/class/scsi_device/2\:0\:0\:0/device/rescan

Then standard procedures to grow the fs apply.

nJoy 😉

 

 

Nginx setting to allow wss sockets to connect

Posted on by admin

General idea of the config

https + proxy pass + virtual host

Nginx as a proxy causes a failure of wss:// connections to the backend server.

add these parameters to the proxy section :

 

proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection “upgrade”;
proxy_set_header Host $host;

Voila’  !!!

😉 nJoy