One of my tasks at work is to check the health/status of multiple Linux servers everyday. I'm thinking of a way to automate this task (without having to login to each server everyday). I'm a newbie system admin by the way. Initially, my idea was to setup a cron job that would run scripts and email the output. Unfortunately, it's not possible to send mail from the servers as of the moment.
I was thinking of running the command in parallel, but I don't know how. For example, how can I see output of df -h without logging in to servers one by one.
You can run ssh with the -t flag to open a ssh session, run a command and then close the session. But to get this fully automated you should automate the login process to every server so that you don't need to type the password for every server.
So to run df -hon a remote server and then close the session you would run ssh -t root#server.com "df -h". Then you can process that output however you want.
One way of automating this could be to write a bash script that runs this command for every server and process the output to check the health of the server.
For further information about the -t flag or how you can automate the login process for ssh.
https://www.novell.com/coolsolutions/tip/16747.html
https://serverfault.com/questions/241588/how-to-automate-ssh-login-with-password
You can use ssh tunnels or just simply ssh for this purpose. With ssh tunnel you can redirect the outputs to your machine, or as an alternative, you can run the ssh with the remote commands on your machine then get the ouput on your machine too.
Please check the following pages for further reading:
http://blog.trackets.com/2014/05/17/ssh-tunnel-local-and-remote-port-forwarding-explained-with-examples.html
https://www.google.hu/amp/s/www.cyberciti.biz/faq/unix-linux-execute-command-using-ssh/amp/
If you want to avoid manual login, use ssh keys.
Create a file /etc/sxx/hosts
populate like so:
[grp_ips]
1.1.1.1
2.2.2.2
3.3.3.3
share ssh key on all machines.
Install sxx from package:
https://github.com/ericcurtin/sxx/releases
Then run command like so:
sxx username#grp_ips "whatever bash command"
Related
I am using local system to learn ssh and what I am trying to do is execute a command on the remote server.
I have ssh server running on terminal1 and client on terminal2.
I used the following command on terminal2:
ssh user1#127.0.0.1 echo Display this.
but it echoes on terminal2. How would I know if the command actually worked if it's not displaying in terminal1?
Thank you.
It worked correctly. It ssh'd into the server, executed the command, and returned the stdout of that command back to you.
SSH gains access to the server, but not necessarily any TTY's active on it. You would have to jump through some hoops to send text to a specific TTY, such as your Terminal1.
A better test would be:
ssh user1#127.0.0.1 'touch ~/testfile'
Then you can check on your server (which is localhost) to see if testfile was created in your user1 home folder. If it did, then the connection and the command succeeded.
What is the best and secure way for a terminal to ping a server for a list of commands to execute every 60 secs? For example, it could download a file (that houses the command) or query a database and then execute what is on there.
Are there more efficient/secure ways to accomplish the above?
Thanks
If you want to make it into a script:
commands.ssh
echo "This will run on the remote machine."
# Do a backup or something...
Then you can execute pass this file to the remote machine using:
ssh user#remote -i id_rsa < commands.ssh
I recommend using an sshkey so that you don't have to keep your login information in the commands file.
Note: make sure the permissions for the commands.ssh file are secure!
chmod 600 commands.ssh
You can use SSH connections which are SSL enabled. If commands are predefined you can depend on a cron job, then you don't need to login to terminal again and again to run it.
My code below doesn't work, when ssh to client and dump log file to the server. Please look at the code below.
ssh 192.168.0.10
dmesg >>/log.txt
You need to include the command to run on the server as part of your ssh command. You can then do the output redirection on the client side:
ssh 192.168.0.10 'dmesg' >> local_file.log
As Khanna111 mentions, this will require a password to be entered (by default), which you can avoid by setting up SSH keys for passwordless login.
How about doing ssh to the client and run the dmesg command and then rsync the logs back. Assuming you can use rsync.
You could also have a CRON that periodically run on the client that invokes dmesg and dumps the log file which can subsequently be copied over. This way you do not have to do an explict ssh.
Another option that I would prefer is to get rysnc to run the command "dmesg" before the transfer. The parameter to use is --rsync-path. The details are explained here: http://www.schwertly.com/2013/07/forcing-rsync-to-create-a-remote-path-using-rsync-path/
EDIT 1: I am assuming that in case of ssh, you have thought about password less logins and the setup they require.
i wanted to execute commands on remote linux box from windows and also wanted to collect result of executed command. Basically i have to pass 2 boxes to execute that command here is flow.
Login to a box
ssh to another box
run command
collect output of command locally (in file)
I tried following
F:\xyz>plink xyz#a1.b1.com -i F:\x\y\PRIVATEKEY.ppk -pw xyz
ssh -f root#166.1.8.1 yum upgrade Cyberc
but this is asking for password. I can do it by adding id_rsa.pub value in to authorized_keys but we dont have permission to do. So instead of that i wanted to write EXPECT script to pass user/pass and commands to complete my job.
Any help on EXPECT script would be much appreciated.
Unless the program on the remote linux host is interactive (i.e. it has prompts that the user must respond to), then you probably don't need to use expect - you can simply use plink to connect to the remote Linux host from your windows machine and run the command. You can specify the username and password to authenticate with the remote host in the plink command. See the following links for more info:
http://the.earth.li/~sgtatham/putty/0.58/htmldoc/Chapter7.html
http://stackoverflow.com/questions/12844944/login-syntax-for-plink-using-ip-username-and-password
I am trying to SSH from one Unix host to another and execute some commands.
Whenever I run ssh hostname <any command> I get back "logname: no login name".
I can succesfully just ssh hostname and then execute the same command without any issues. SSH is setup to use rsa keys for password-less connections.
Everything works fine using a different user account so I suspect it might be related to bash profile or something along those lines? I would appreciate any pointers.