wsl -h shows the following:
--exec, -e <CommandLine> Execute the specified command without using the default Linux shell.
-- Pass the remaining command line as is.
What does "without using the default Linux shell" mean (i.e. what else is it going to use, if not the default shell!?)?.
Additionally, by way of an example, I now have three possible ways to run Linux ls from my PowerShell prompt (i.e. this will not be Get-ChildItem aliased to ls, but instead a Linux command via WSL):
PS C:\> wsl -e ls # Alternatively, wsl --exec ls
PS C:\> wsl -- ls
PS C:\> wsl ls
But all outputs appear to be the same. How would you explain the differences between these three ways of running a WSL Linux command from a PowerShell prompt?
I think it means wsl runs the command directly, instead of spawning a shell process to run the command.
For example, if I run :
wsl -e sleep 10
From another terminal, I have :
root 1482 1 0 11:32 tty3 00:00:00 /init
ubuntu 1483 1482 0 11:32 tty3 00:00:00 sleep 10
We can see /init is the parent of sleep 10, without a shell in between.
A cool trick is using this to set the X11 $DISPLAY variable, letting you use windows terminal to get remote shells using WSLG.
# in microsoft terminal or powershell use this command line
wsl.exe -- ssh -a -X -Y $hostname
then on the remote system
# DISPLAY will show something like localhost:10.0 on the remote system
echo $DISPLAY
# use a program like xeyes to test
xeyes
I'm running the following command for an automation with interactive connection after the automation run (my full automation has other commands), for example:
ssh user#ip 'ls -la; bash'
and for some reason I don't have a complete tty like normal ssh connection (user#hostname:~$ and autocomplete)
As the ssh man page says:
-t Force pseudo-tty allocation. This can be used to execute arbi-
trary screen-based programs on a remote machine, which can be
very useful, e.g. when implementing menu services. Multiple -t
options force tty allocation, even if ssh has no local tty.
So you have to use
ssh -tt user#ip 'ls -la; bash'
If I do
ssh -f 10.10.47.47 "/opt/omni/bin/mbuffer -4 -v 0 -q -I 8024 | /usr/sbin/zfs receive tank/test"
then I have to press CTRL-D to exit an extra shell that have been spawned on the Linux host, where I ran the ssh command.
If I do
ssh -f 10.10.47.47 "sleep 10s"
and then try to CTRL-D than the Linux host hangs until the sleep command exits on the remote host. Very weird behaviour, which I wouldn't expect since -f was used.
Question
Is it possible to avoid this extra shell on the host where the ssh command is executed?
I am using linux pc and installed tshark . And have to capture packets in eth1 interface using TCL script. But tshark is running in root mode. Capturing and script running pc's are same. How to login as root and how to run tshark commands using TCL ? Please provide me a solution for this.
#!/usr/bin/tclsh
set out [exec tshark -V -i eth1 arp -c 1 ]
puts $out
Output
test#test:~$ tclsh pcap.tcl
Capturing on eth1
tshark: The capture session could not be initiated (eth1: You don't have permission to capture on that device (socket: Operation not permitted)).
Please check to make sure you have sufficient permissions, and that you have the proper interface or pipe specified.
0 packets captured
while executing
"exec tshark -V -i eth1 arp -c 1 "
invoked from within
"set out [exec tshark -V -i eth1 arp -c 1 ]"
(file "pcap.tcl" line 5)
test#test:~$
please try below steps and also refer this link http://packetlife.net/blog/2010/mar/19/sniffing-wireshark-non-root-user/
root#test:/usr/bin# setcap cap_net_raw,cap_net_admin=eip /usr/bin/dumpcap
root#test:/usr/bin# getcap /usr/bin/dumpcap
/usr/bin/dumpcap = cap_net_admin,cap_net_raw+eip
root#test:/usr/bin# exit
exit
test#test:/usr/bin$ tshark -V -i eth1
Capturing on eth1
Frame 1 (60 bytes on wire, 60 bytes captured)
Arrival Time: Aug 8, 2013 13:54:27.481528000
[Time delta from previous captured frame: 0.000000000 seconds]
[Time delta from previous displayed frame: 0.000000000 seconds]
You have to either elevate the privileges of your tshark process via sudo (or any other available means) or run your whole script with elevated privileges.
One way to do that which might be simpler than sudo as it would require zero customizations is to write a super-simple C program which would just run /usr/bin/tshark with the necessary arguments and then make that program setuid root and distribute along with your Tcl program. That is only needed if you need portability. Otherwise sudo is much simpler.
I have two questions:
There are multiple remote linux machines, and I need to write a shell script which will execute the same set of commands in each machine. (Including some sudo operations). How can this be done using shell scripting?
When ssh'ing to the remote machine, how to handle when it prompts for RSA fingerprint authentication.
The remote machines are VMs created on the run and I just have their IPs. So, I cant place a script file beforehand in those machines and execute them from my machine.
There are multiple remote linux machines, and I need to write a shell script which will execute the same set of commands in each machine. (Including some sudo operations). How can this be done using shell scripting?
You can do this with ssh, for example:
#!/bin/bash
USERNAME=someUser
HOSTS="host1 host2 host3"
SCRIPT="pwd; ls"
for HOSTNAME in ${HOSTS} ; do
ssh -l ${USERNAME} ${HOSTNAME} "${SCRIPT}"
done
When ssh'ing to the remote machine, how to handle when it prompts for RSA fingerprint authentication.
You can add the StrictHostKeyChecking=no option to ssh:
ssh -o StrictHostKeyChecking=no -l username hostname "pwd; ls"
This will disable the host key check and automatically add the host key to the list of known hosts. If you do not want to have the host added to the known hosts file, add the option -o UserKnownHostsFile=/dev/null.
Note that this disables certain security checks, for example protection against man-in-the-middle attack. It should therefore not be applied in a security sensitive environment.
Install sshpass using, apt-get install sshpass then edit the script and put your linux machines IPs, usernames and password in respective order. After that run that script. Thats it ! This script will install VLC in all systems.
#!/bin/bash
SCRIPT="cd Desktop; pwd; echo -e 'PASSWORD' | sudo -S apt-get install vlc"
HOSTS=("192.168.1.121" "192.168.1.122" "192.168.1.123")
USERNAMES=("username1" "username2" "username3")
PASSWORDS=("password1" "password2" "password3")
for i in ${!HOSTS[*]} ; do
echo ${HOSTS[i]}
SCR=${SCRIPT/PASSWORD/${PASSWORDS[i]}}
sshpass -p ${PASSWORDS[i]} ssh -l ${USERNAMES[i]} ${HOSTS[i]} "${SCR}"
done
This work for me.
Syntax : ssh -i pemfile.pem user_name#ip_address 'command_1 ; command 2; command 3'
#! /bin/bash
echo "########### connecting to server and run commands in sequence ###########"
ssh -i ~/.ssh/ec2_instance.pem ubuntu#ip_address 'touch a.txt; touch b.txt; sudo systemctl status tomcat.service'
There are a number of ways to handle this.
My favorite way is to install http://pamsshagentauth.sourceforge.net/ on the remote systems and also your own public key. (Figure out a way to get these installed on the VM, somehow you got an entire Unix system installed, what's a couple more files?)
With your ssh agent forwarded, you can now log in to every system without a password.
And even better, that pam module will authenticate for sudo with your ssh key pair so you can run with root (or any other user's) rights as needed.
You don't need to worry about the host key interaction. If the input is not a terminal then ssh will just limit your ability to forward agents and authenticate with passwords.
You should also look into packages like Capistrano. Definitely look around that site; it has an introduction to remote scripting.
Individual script lines might look something like this:
ssh remote-system-name command arguments ... # so, for exmaple,
ssh target.mycorp.net sudo puppet apply
The accepted answer sshes to machines sequentially. In case you want to ssh to multiple machines and run some long-running commands like scp concurrently on them, run the ssh command as a background process.
#!/bin/bash
username="user"
servers=("srv-001" "srv-002" "srv-002" "srv-003");
script="pwd;"
for s in "${servers[#]}"; do
echo "sshing ${username}#${s} to run ${script}"
(ssh ${username}#${s} ${script})& # Run in background
done
wait # If removed, you can run some other script here
If you are able to write Perl code, then you should consider using Net::OpenSSH::Parallel.
You would be able to describe the actions that have to be run in every host in a declarative manner and the module will take care of all the scary details. Running commands through sudo is also supported.
For this kind of tasks, I repeatedly use Ansible which allows to duplicate coherently bash scripts in several containets or VM. Ansible (more precisely Red Hat) now has an additional web interface AWX which is the open-source edition of their commercial Tower.
Ansible: https://www.ansible.com/
AWX:https://github.com/ansible/awx
Ansible Tower: commercial product, you will probably fist explore the free open-source AWX, rather than the 15days free-trail of Tower
There is are multiple ways to execute the commands or script in the multiple remote Linux machines.
One simple & easiest way is via pssh (parallel ssh program)
pssh: is a program for executing ssh in parallel on a number of hosts. It provides features such as sending input to all of the processes, passing a password to ssh, saving the output to files, and timing out.
Example & Usage:
Connect to host1 and host2, and print "hello, world" from each:
pssh -i -H "host1 host2" echo "hello, world"
Run commands via a script on multiple servers:
pssh -h hosts.txt -P -I<./commands.sh
Usage & run a command without checking or saving host keys:
pssh -h hostname_ip.txt -x '-q -o StrictHostKeyChecking=no -o PreferredAuthentications=publickey -o PubkeyAuthentication=yes' -i 'uptime; hostname -f'
If the file hosts.txt has a large number of entries, say 100, then the parallelism option may also be set to 100 to ensure that the commands are run concurrently:
pssh -i -h hosts.txt -p 100 -t 0 sleep 10000
Options:
-I: Read input and sends to each ssh process.
-P: Tells pssh to display output as it arrives.
-h: Reads the host's file.
-H : [user#]host[:port] for single-host.
-i: Display standard output and standard error as each host completes
-x args: Passes extra SSH command-line arguments
-o option: Can be used to give options in the format used in the configuration file.(/etc/ssh/ssh_config) (~/.ssh/config)
-p parallelism: Use the given number as the maximum number of concurrent connections
-q Quiet mode: Causes most warning and diagnostic messages to be suppressed.
-t: Make connections time out after the given number of seconds. 0 means pssh will not timeout any connections
When ssh'ing to the remote machine, how to handle when it prompts for
RSA fingerprint authentication.
Disable the StrictHostKeyChecking to handle the RSA authentication prompt.
-o StrictHostKeyChecking=no
Source: man pssh
This worked for me. I made a function. Put this in your shell script:
sshcmd(){
ssh $1#$2 $3
}
sshcmd USER HOST COMMAND
If you have multiple machines that you want to do the same command on you would repeat that line with a semi colon. For example, if you have two machines you would do this:
sshcmd USER HOST COMMAND ; sshcmd USER HOST COMMAND
Replace USER with the user of the computer. Replace HOST with the name of the computer. Replace COMMAND with the command you want to do on the computer.
Hope this helps!
You can follow this approach :
Connect to remote machine using Expect Script. If your machine doesn't support expect you can download the same. Writing Expect script is very easy (google to get help on this)
Put all the action which needs to be performed on remote server in a shell script.
Invoke remote shell script from expect script once login is successful.