Objective:
=========
connect to server1 as root and execute commands and postprocess the command output to get a list of servers (let's say this is server2)
change to non-root user in server1
3)connect to server2 as a non-root user via server1
change to root user on server2
execute commands on server2 and from the output of the command, build another command and run it
==========
I wrote a program using pexpect/pxssh. However, the program is awfully slow while I run commands on server-2
Would you please advise to resolve this issue? Any alternative is welcome.
Regards,
Ashish
Related
I am trying to connect to a MySQL server, which is restricted by being connected to a given server. I am trying to connect through this restricting server while not physically connected.
Through the command line this is doable by creating a SSH connection, after which I can run MySQL commands from the command line. For example:
ssh myUsername#Hostname
myUsername#Hostname's password:
[myUsername#Host ~]$ mysql -h mySQLHost -u mySQLUsername -p mySQLPassword
However, I wish to connect to the MySQL database from within R, so I can send queries to read in tables into my current R session. Usually I would run a R session inside of the commandline, but the server does not have R installed on it.
For example, I have this snippet of code that work when I am physically connected to the server (filled in information changed):
myDB <- dbConnect(MySQL(), user="mySQLUsername", password="mySQLPassword", dbname="myDbname", host="mySQLHost")
In essence, I want to run this same command through a pipe, so that the myDB object is a working mySQL connection.
I have been trying to pipe my way into the restricting server from within R, and have been able to read in a csv file. For example:
dat <- read.table(pipe('ssh myUsername#Hostname "cat /path/to/your/file"'))
This prompts me for my password, and the table is read (as is suggested it would here). However, I am unsure how to translate this to a MySQL connection. For example, should I make the pipe part of the host argument? That was my first thought, but have been unable to make that work.
Any help would be appreciated.
I accomplish a similar task with Postgres using SSH tunneling. Effectively, what you're doing with an SSH tunnel is saying "establish a connection to the remote server, and make a port from that server available as a port on my local machine."
You can set up a SSH tunnel using the following command on your local machine:
ssh -L local_port:lochalhost:remote_port username#remote_host
Specifically, what you're doing with this command is creating a Local Port Forwarding SSH tunnel, which is taking the port you'd connect to directly on the machine with your database installed (remote_port), and securely sending it to the machine you have R installed on as local_port.
For example, for a database server with the following options:
hostname: 192.168.1.3
username: mysql
server mysql port: 3306
You could use the following command (at the command line, or in R using system2) to create a tunnel to port 9000 on your machine:
ssh -L 9000:localhost:3306 mysql#192.168.1.3
Depending on what your exact DBI connection looks like in R, you may have to edit the connection configuration slightly to make it connect to your newly created tunneling port. The reason why I use a different localhost port is that it prevents conflicts with a local version of the database, if you've got one.
I have small example script (script_p.r) like the following, which in intend run in terminal.
#!/usr/bin/Rscript
sink("output_capture.txt")
mn <- mean(1:10)
# and so on, much longer list of tasks
I want to run this script remotely with other iMac host computer (ip address e.g.. not real : 111.111.111.111) which allows me to log in and work (e.g., not real. username user101, password p12334)
Is this way to run this script remotely (say using ssh), say from other computer with ip address: 222.222.222.222 and user name user102 ?
First, put script_p.r on the remote machine.
Then either just do:
ssh user102#222.222.222.222
user102:-$ ./script_p.r
or ssh user102#222.222.222.222 'script_p.r'
or put it in a script:
runremote.sh :
#!/bin/bash
ssh user102#222.222.222.222 'script_p.r'
and run locally
user101:-$ ./runremote.sh
on my server dmgr is down, how can I stop/start the application running on server1?
wsadmin script throwing exception.
Thanks
SF
Use the -host and -port options of wsadmin to point to server1.
Alternatively, restart the dmgr.
If servers is federated, we can't connect to server directly. we need dmgr and nodeagent running to stop/start only application.
or
Server has to be standalone.
Thanks
-SR
I am facing difficulty in executing MPI program on two machines. The OS is Ubuntu 12.04. And the MPI implementation is MPICH2
ssh is working fine:
root#ubuntu:/home# ssh 192.168.1.9
root#gpuguy's password:
Welcome to Ubuntu 12.04.3 LTS (GNU/Linux 3.8.0-29-generic i686)
* Documentation: https://help.ubuntu.com/
131 packages can be updated.
67 updates are security updates.
Last login: Thu Oct 24 17:36:25 2013 from ubuntu.local
root#gpuguy:~#
But when I run my MPI programs it fails:
root#ubuntu:/home# mpiexec -f hosts.cfg -n 4 hello
root#192.168.1.9's password:
[proxy:0:0#gpuguy] HYDU_sock_connect (./utils/sock/sock.c:171): unable to get host address for ubuntu (1)
[proxy:0:0#gpuguy] main (./pm/pmiserv/pmip.c:209): unable to connect to server ubuntu at port 42104 (check for firewalls!)
I have already disabled firewall on both machines that is the reason I can do ssh successfully. But how to solve this issue?
My MPI code runs successfully on single machine.
For MPICH (or any MPI implementation) to work, you need to have passwordless SSH set up. I should also mention that you really shouldn't have to be logged in as root to make this work. It's generally a very bad idea to be logged in as root all of the time.
In /etc/hosts file, add ip address of each server and its hostname.
You should do this for all the servers.
for example:
10.10.0.5 server1
10.10.0.6 server2
10.10.0.7 server3
Just check in /etc/hosts file, not use tab (\t) instead of space to separate between ip address and hostname.
This is wrong:
10.10.0.5 \t server1
This is true:
10.10.0.5 server1
Be careful to not delete or modify existed lines in /etc/hosts file. only add new lines at end of file.
Also, you do not need to disable firewall to fix this issue.
I am trying to kickstart a newly built VM. I am stuck with the following.
Want to start with a console so that I can include username and other info for this VM:
#vmhost02 ~]$ sudo virsh start --console testengine
Domain testengine started
Connected to domain testengine
Escape character is ^]
It hangs up in there and doesn't listen to any keys except "^]"
Let me know if you need more information for any ideas...
Thanks very much.
1)
You can try to edit /etc/default/grub in the guest, and make sure you have:
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1"
Then execute:
# update-grub
# reboot
2)
If that does not work, try to replace quiet with console=ttyS0 in GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub:
GRUB_CMDLINE_LINUX_DEFAULT="... console=ttyS0"
Then again:
# update-grub
# reboot
3)
You may still need to try:
# systemctl enable serial-getty#ttyS0.service
# systemctl start serial-getty#ttyS0.service
# reboot
You would need to define a tty to be used as a virtual console. In case you have access to your vm either using vnc or ssh create the following file
vi /etc/init/ttyS0.conf
The content should be something like
start on stopped rc RUNLEVEL=[2345]
stop on runlevel [!2345]
respawn
exec /sbin/getty -L 38400 ttyS0 vt102 # This is your term type vt102
Save these settings and subsequently from your host machine
virsh destroy [vm-name]; service libvirtd stop; service libvirtd start; virsh start [vm-name]
I'm doing here a stop/start of libvirt, because it sometimes tend to not send a SIGTERM to libvirt.
Finally try
virsh console [vm-name]
May be simpler than the solution of val0x00ff, you shall add the console=ttyS0 at the end of the kernel lines in the /boot/grub2/grub.cfg file of the VM (this is not done by default it seems):
(vm)$> grubby --update-kernel=ALL --args="console=ttyS0"
(vm)$> reboot
Then virsh console shall work as expected.