I am running a cronjob for rsyncing my hard drive with a folder on a server within my companies network. This happens on my laptop which I also use outside that network.
My crontab looks like this:
*/30 * * * * rsync --delete -azvv -e ssh /Users/user/Work/Folder user#server:/home/user/BACKUP/
How can I make cron running this job only when the server is available?
Many thanks!
First you need a way to determine if your server is available or not. ping might be sufficient but is probably not ideal. As poor man's solution you could prepend your original command like this:
ping -c2 server >/dev/null 2>&1 && rsync --delete...
This means that cron will run rsync only if ping has been successful.
Related
I am trying to use parallel on multiple server using ssh, what actually I would like to do is something like:
parallel -s computer_list.txt < command.txt
where in server_list.txt there is list of server and in command.txt looks like
fist_job.sh
second_job.sh
...
But I don't want that all the server do all the jobs in the list, I want that each *.sh is executed just one time on a random server, all of them can reach all files that they need to execute each command.
In other words what I am looking for is a kind of generalization of:
parallel < command.txt
I guess you could do something like this:
servers.txt
server1
server2
server3
server4
serverA
serverB
raspi10
raspi11
raspi12
raspi13
supercomputerA
supercomputerB
jobs.txt
job1
job2
job3
job4
job5
job6
Then use this bash script:
#!/bin/bash
# Read in list of jobs into array
jobs=( $(<jobs.txt) )
# Get randomised list of servers
servers=( $( gshuf servers.txt) )
# Assign each job to a server and execute in parallel
for ((i==0;i<${#jobs[#]};i++)) ; do
echo "ssh \"${servers[i]}\" \"${jobs[i]}\""
done | parallel
Example
That generates the following input for GNU Parallel:
ssh "raspi12" "job1"
ssh "serverA" "job2"
ssh "serverB" "job3"
ssh "raspi13" "job4"
ssh "server3" "job5"
ssh "supercomputerB" "job6"
Notes:
gshuf is how GNU shuf (shuffle) is installed on a Mac. It may be known as shuf on other machines.
This works for me:
parallel --slf computer_list.txt < command.txt
I use version 20180822.
I've got,
My laptop
A remote server I can SSH into which has a Docker volume inside of which are some files I'd like to copy to my laptop.
What is the best way to copy these files over? Bonus points for using things like rsync, etc.. which are fast / can resume / show me progress and not writing any temporary files.
Note: my user on the remote server does not have permission to just scp the data straight out of the volume mount in /var/lib/docker, although I can run any containers on there.
Having this problem, I created dvsync which uses ngrok to establish a tunnel that is being used by rsync to copy data even if the machine is in a private VPC. To use it, you first start the dvsync-server locally, pointing it at the source directory:
$ docker run --rm -e NGROK_AUTHTOKEN="$NGROK_AUTHTOKEN" \
--mount source=MY_DIRECTORY,target=/data,readonly \
quay.io/suda/dvsync-server
Note, you need the NGROK_AUTHTOKEN which can be obtained from ngrok dashboard. Then start the dvsync-client on the target machine:
docker run -e DVSYNC_TOKEN="$DVSYNC_TOKEN" \
--mount source=MY_TARGET_VOLUME,target=/data \
quay.io/suda/dvsync-client
The DVSYNC_TOKEN can be found in dvsync-server output and it's a base64 encoded private key and tunnel info. Once the data has been copied, the client wil exit.
I'm not sure about the best way of doing so, but if I were you I would run a container sharing the same volume (in read-only -- as it seems you just want to download the files within the volume) and download theses.
This container could be running rsync as you wish.
I have a script which loops through a list of hosts, connecting to each of them with SSH using an RSA key, and then saving the output to a file on my local machine - this all works correctly. However, the commands to run on each server take a while (~30 minutes) and there are 10 servers. I would like to run the commands in parallel to save time, but can't seem to get it working. Here is the code as it is now (working):
for host in $HOSTS; do
echo "Connecting to $host"..
ssh -n -t -t $USER#$host "/data/reports/formatted_report.sh"
done
How can I speed this up?
You should add & to the end of the ssh call, it will run on the background.
for host in $HOSTS; do
echo "Connecting to $host"..
ssh -n -t -t $USER#$host "/data/reports/formatted_report.sh" &
done
I tried using & to send the SSH commands to the background, but I abandoned this because after the SSH commands are completed, the script performs some more commands on the output files, which need to have been created.
Using & made the script skip directly to those commands, which failed because the output files were not there yet. But then I learned about the wait command which waits for background commands to complete before continuing. Now this is my code which works:
for host in $HOSTS; do
echo "Connecting to $host"..
ssh -n -t -t $USER#$host "/data/reports/formatted_report.sh" &
done
wait
Try massh http://m.a.tt/er/massh/. This is a nice tool to run ssh across multiple hosts.
The Hypertable project has recently added a multi-host ssh tool. This tool is built with libssh and establishes connections and issues commands asynchronously and in parallel for maximum parallelism. See Multi-Host SSH Tool for complete documentation. To run a command on a set of hosts, you would run it as follows:
$ ht ssh host00,host01,host02 /data/reports/formatted_report.sh
You can also specify a host name or IP pattern, for example:
$ ht ssh 192.168.17.[1-99] /data/reports/formatted_report.sh
$ ht ssh host[00-99] /data/reports/formatted_report.sh
It also supports a --random-start-delay <millis> option that will delay the start of the command on each host by a random time interval between 0 and <millis> milliseconds. This option can be used to avoid thundering herd problems when the command being run accesses a central resource.
Currently, I have two servers running on an EC2 instance (MongoDB and bottlepy). Everything works when I SSHed to the instance and started those two servers. However, when I closed the SSH session (the instance is still running), I lost those two servers. Is there a way to keep the server running after logging out? I am using Bitvise Tunnelier on Windows 7.
The instance I am using is Ubuntu Server 12.04.3 LTS.
For those landing here from a google search, I would like to add tmux as another option. tmux is widely used for this purpose, and is preinstalled on new Ubuntu EC2 instances.
Managing a single session
Here is a great answer by Hamish Downer given to a similar question over at askubuntu.com:
I would use a terminal multiplexer - screen being the best known, and tmux being a more recent implementation of the idea. I use tmux, and would recommend you do to.
Basically tmux will run a terminal (or set of terminals) on a computer. If you run it on a remote server, you can disconnect from it without the terminal dying. Then when you login in again later you can reconnect, and see all the output you missed.
To start it the first time, just type
tmux
Then, when you want to disconnect, you do Ctrl+B, D (ie press Ctrl+B, then release both keys, and then press d)
When you login again, you can run
tmux attach
and you will reconnect to tmux and see all the output that happened. Note that if you accidentally lose the ssh connection (say your network goes down), tmux will still be running, though it may think it is still attached to a connection. You can tell tmux to detach from the last connection and attach to your new connection by running
tmux attach -d
In fact, you can use the -d option all the time. On servers, I have this in my >.bashrc
alias tt='tmux attach -d'
So when I login I can just type tt and reattach. You can go one step further >if you want and integrate the command into an alias for ssh. I run a mail client >inside tmux on a server, and I have a local alias:
alias maileo='ssh -t mail.example.org tmux attach -d'
This does ssh to the server and runs the command at the end - tmux attach -d The -t option ensures that a terminal is started - if a command is supplied then it is not run in a terminal by default. So now I can run maileo on a local command line and connect to the server, and the tmux session. When I disconnect from tmux, the ssh connection is also killed.
This shows how to use tmux for your specific use case, but tmux can do much more than this. This tmux tutorial will teach you a bit more, and there is plenty more out there.
Managing multiple sessions
This can be useful if you need to run several processes in the background simultaneously. To do this effectively, each session will be given a name.
Start (and connect to) a new named session:
tmux new-session -s session_name
Detach from any session as described above: Ctrl+B, D.
List all active sessions:
tmux list-sessions
Connect to a named session:
tmux attach-session -t session_name
To kill/stop a session, you have two options. One option is to enter the exit command while connected to the session you want to kill. Another option is by using the command:
tmux kill-session -t session_name
If you don't want to run some process as a service (or via an apache module) you can (like I do for using IRC) use gnome-screen Install screen http://hostmar.co/software-small.
screen keeps running on your server even if you close the connection - and thus every process you started within will keep running too.
It would be nice if you provided more info about your environment but assuming it's Ubuntu Linux you can start the services in the background or as daemons.
sudo service mongodb start
nohup python yourbottlepyapp.py &
(Use nohup if you want are in a ssh session and want to prevent it from closing file descriptors)
You can also run your bottle.py app using Apache mod_wsgi. (Running under the apache service) More info here: http://bottlepy.org/docs/dev/deployment.html
Hope this helps.
Addition: (your process still runs after you exit the ssh session)
Take this example time.py
import time
time.sleep(3600)
Then run:
$ python3 time.py &
[1] 3027
$ ps -Af | grep -v grep | grep time.py
ubuntu 3027 2986 0 18:50 pts/3 00:00:00 python3 time.py
$ exit
Then ssh back to the server
$ ps -Af | grep -v grep | grep time.py
ubuntu 3027 1 0 18:50 ? 00:00:00 python3 time.py
Process still running (notice with no tty)
You will want the started services to disconnect from the controlling terminal. I would suggest you use nohup to do that, e.g.
ssh my.server "/bin/sh -c nohup /path/to/service"
you may need to put an & in there (in the quotes) to run it in the background.
As others have commented, if you run proper init scripts to start/stop services (or ubuntu's service command), you should not see this issue.
If on Linux based instances putting the job in the background followed by disown seems to do the job.
$ ./script &
$ disown
I'm dealing with a crappy ISP that resets my WAN connection at random points while my script is running. I want the transfer to survive this reset and go on. I manually launch this script vs using cron / launchd currently.
I have a fairly basic script as shown below:
rsync -rltv --progress --partial -e "ssh -i <key> -o ConnectTimeout=300" <remotedir> <localdir>
Am I better off putting the timeout in the rsync section instead?
For example:
rsync -rltv --progress--partial --timeout=300 -e "ssh -i <key>" <remotedir> <localdir>
Thanks!
ConnectTimeout only applies when SSH is trying to establish the connection with the server, it doesn't have anything to do with timeouts during the data transfer. So you need to use the --timeout option to do what you want.
Try re-running the rsync. Also try without the ssh option. The job failed probably due to losing your network connection. I have an rsync job copying files between datacenters running every 2 hours via cron and it will fail about once per day.