I have a bash script that I have to regularly run on a remote server. Part of the script includes running a backup which takes a while, and after it has run, I have to hit "Y" to confirm that the backup worked before the script will continue.
I would like to know if there is a way to get my laptop to make a beep (or some sort of sound) when that happens. I know that echo -e '\a' makes a beep, but if I run it from within a script on the remote server, the beep happens on the remote server.
I have control of the script that is being run, so I could easily change it to do something special.
You could send the command through ssh back to your computer like:
ssh user#host "echo -e '\a'"
Just make sure you have ssh key authentication from your server to your computer so the command can run smoothly
In my case the offered solutions with echo didn't work. I'm using a macbook and connect to an ubuntu system. I keep the terminal open and I'd like to be informed when a long running bash script is ready.
What I did notice is that if I shutdown the remote system then it will beep the macbook and show an alarm icon on the relevant tab. So I have now implemented a bit of dirty workaround:
sudo shutdown 1440 && shutdown -c
This will initiate the system to shutdown and will immediately cancel the request. And I do get the alarm beep + icon. You will need to setup sudo to allow the user to permit shutdown. As it was my own remote server it was no problem but could limit the usability for others.
Ive been trying to figure out when to set my script to initiate and what to use as After= parameter.
What i need is to initiate my service as late as possible... kind of like the last service in the stack. I def. need /home to be mounted. I cant rely on wpa_supplicant nor mdns since it is not given those have been configured on the device.
Ive also read systemd docs but could not figure out what service to set to After= option in service file.
After=ABC.service
means you service will launch after launching ABC.service, but it is not guarantied, so to ensure you service starts only after ABC.service use
Requires=ABC.service
OR
You can use below script to achieve this.
Create a file at any location of your device once home is getting mounted, and then launch your service
[Service]
Type=oneshot
ExecStart=/bin/ABC -c 'while [ ! -e /tmp/YOUR_FILE ]; do sleep 0.1 ; done'
ABC is your executable of service, it will wait till it doesn't get YOUR_FILE at /tmp/ location.
Hope this helps.
I've been experimenting with Pis for a little while now and am close to completing my first project, I have all the bits working but I'm struggling to put them all together into an automated process.
Basically I have a Pi setup to run a fbi slideshow from a specific folder and I want it to constantly be looking for a pre established Wifi network and when it finds this network it needs to run an update script. I've got these two bits working.
From here, I want the Pi to be turned on and load straight into fbi whilst running the checking script in the background, if the checking script finds the Wifi network then it will run as normal (preferably without ending the slideshow) and when it's done fbi should have an updated selection of images to run (if a restart of fbi is necessary then so be it).
I'm coming up short on achieving this. I can run one script or the other, and if I automate the checking script (cron hasn't worked though I dare say I'm doing something wrong) with rc.local it just gets stuck in a checking loop before login, which kinda makes sense given the script.
Here's the monitoring script:
#!/bin/bash
while true ; do
if ifconfig wlan0 | grep -q "inet addr:" ; then
echo "Wifi connected!"
echo "Initiating Grive sync!"
(cd /home/pi/images/; ./grive -s Pi_Test -V)
sleep 60
else
echo "Wifi disconnected! Attempting to reconnect now."
ifup --force wlan0
sleep 10
fi
done
and in case it's relevant, here's the command the run the fbi slideshow:
fbi -noverbose -a -t 10 -u /home/pi/images/Pi_Test/*.jpg
I do not have a Pi but I have used cron on my VPS which is running a CentOS, but the overall procedure should be similar.
To have some script to be executed by cron, you need to:
Edit /etc/cron.allow
You need to add in your user id to this file so that you can use crontab.
crontab -e
Use this command to add rules you want to fire.
From your description, it seems to me that you already know the syntax to add rules into cron table.
After that, you can use crontab -l to verify your change.
As for stuck at before login, that is very likely due to the while loop. You might want to get rid of the while and sleep because cron is helping you out by invoking your script periodically.
Therefore the following should not suffer from the stuck issue.
if ifconfig wlan0 | grep -q "inet addr:" ; then
echo "Wifi connected!"
echo "Initiating Grive sync!"
(cd /home/pi/images/; ./grive -s Pi_Test -V)
else
echo "Wifi disconnected! Attempting to reconnect now."
ifup --force wlan0
fi
The trick instead, is to have some line similar to this in your cron table
*/1 * * * * /home/David_Legassick/test.sh
The */1 asks cron to call your script test.sh every minute.
I'm running a Bukkit (Minecraft) server on a Linux machine and I want to have the server gracefully shut down using the server's stop command and the computer suspend at a certain time using pm-suspend from the command line. Here's what I've got:
me#comp~/dir$ perl -e 'sleep [time]; print "stop\\n";' | ./server && sudo pm-suspend
(I've edited by /etc/sudoers so I don't have to enter my password when I suspend.)
The thing is, while the perl -e is sleeping, the server is expecting a constant stream of bytes, (That's my guess. I could be misunderstanding something.) so it prints out all of the nothings it receives, taking up precious resources:
me#comp~/dir$ ...
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>...
Is there any such thing as a buffered pipe? If not, are there any ways to send delayed input to a script?
You may want to have a look at Bukkit's wiki, which recommends an init script for permanently running servers.
This init script uses rather unconventional approach to communicate with running server. The server is started in screen session, then all commands are send to the server console via screen, e.g.
screen -p 0 -S $SCREEN -X eval 'stuff \"stop\"\015'
See https://github.com/Ahtenus/minecraft-init/blob/master/minecraft
This approach suggest that bukkit may be expecting standard input to be attached to a terminal, thus requiring screen wrapper (which is itself terminal emulator) for unattended runs.
I'm trying to write a shell script that automates certain startup tasks based on my location (home/campusA/campusB). I go to University and take classes in two different campuses (hence campusA/campusB). My location is determined by which wireless network I'm connected to. For the purposes of this script, we can assume that I will be connected to one of these networks when the script is called and my script knows which one I'm connected to based on a call to iwconfig.
This is what I want it to do:
cat file1 > file2 # always do this, regardless of where I am
if Im at home:
start tweetdeck, thunderbird, skype
else if Im at campusA:
activate the login script # I need to login on a webform before I get internet access.
# I have written a script to automate this.
# Wait for this script to finish before doing anything else
myProg2 & # I want myProg2 running in the background until I shutdown my computer.
else if Im at campusB:
ssh username#domain # this is the problematic line
myProg2 & # I want myProg2 running in the background until I shutdown my computer.
start tweetdeck, thunderbird
close the terminal with the "exit" command
The problem is that campusB's wireless network is behind a firewall, which grants me internet access ONLY after I successfully ssh by username#domain. After a successful ssh, I need to keep the terminal window active in order to hold keep the internet access. If I close the terminal window, I lose internet access (this is bad).
When I try doing just ssh username#domain, the script stops because I don't exit the ssh command. I can't ^C out of it, which means that the rest of the script is never executed. I also have the same problem if I just close the terminal window in an attempt to kill the ssh session.
Some googling brought me to subshell, which I'm either using wrong or can't use to solve my problem. So how should I go about solving this problem? I'd appreciate any help - I've been at this for a while now and am unable to find anything helpful. If it makes a difference, I'd rather not store my ssh password in the script
Further, ampersanding the ssh call (ssh username#domain &) doesn't seem to do any good (can anyone explain why?)
Thank you in advance
EDIT
I must clarify, that the ssh connection has to be active in order for me to have internet access. Thus, when I close the terminal window, I need the ssh connection to still be active.
I had a script that looped on 6 servers, calling via ssh in the background. In 1 part of the script, there was a mis-behaving vendor application; the application didn't 'let go' of the connection properly. (other parts of the script using ssh in background worked fine).
I found that using ssh -t -t cured the problem. Maybe this can help you too.
(a teammate found this on the web, and we had spent so much time, I never went back to read the article that suggested this. The man page on our system gave no hint that such a thing was possible)
Hope this helps.
You may want to try to double background myProg2 to detach it from the tty:
# cf. "Wizard Boot Camp, Part Six: Daemons & Subshells",
# http://www.linux-mag.com/id/5981
(myProg2 &) &
Another option may be to use the daemon tool from the libslack package:
http://ingvar.blog.linpro.no/2009/05/18/todays-sysadmin-tip-using-libslack-daemon-to-daemonize-a-script/
Having a ssh with pseudy tty on background shell
In addition to #shellter's answer, I would like make some precision:
where #shelter said:
The man page on our system gave no hint that such a thing was possible
On my system (Debian 7 GNU/Linux), if I hit:
man -Pcol\ -b ssh| grep -A3 '^ *-t '
I could read:
-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.
Yes: Multiple -t options force tty allocation, even if ssh has no local tty.
This mean: If you remotely run a tool that require access to pseudo terminal ( pty like /dev/pts/0), you could run them by using -t switch.
But this would work only if ssh is run from a shell console (aka having his own pty). If you plan to run them is shell session without console, like background scripts, you may use Multiple -t to enforce pseudo tty allocation from ssh.
Multiple ssh shell on one ssh connection
In addition to answers from #tommy and #geekosaur, I would make some precision:
#tommy point to a very intersting feature of ssh. Not sure this have a lot to do with answer, but speaking around long time connection, this feature has to be clearly understood.
Once a connection is established, ssh could (and know how to) use them to drive a lot of thing in this one connection:
-L let you drive remote TCP connections to local machines/network. (full syntax is: -L localip:localport:distip:distport) where localip could be specified to permit other hosts from same local domain to access same tcp bind, and distip could by any host from distant network ( not only localhost ) sample: -L192.168.1.31:8443:google.com:443 permit any host from local domain to reach google through your host: http://192.168.1.31:8443
-R Same remarks in reverse way!
-M Tell ssh to open a local unix socket for bindind next ssh consoles. Simply open two terminal window. First in both window, hit: ssh somewhere than hit netstat -tan | grep :22 or netstat -tan | grep 192.168.1.31:22 (assuming 192.168.1.31 is your onw host's ip)
Than compare close all your ssh session and in first terminal, hit: ssh -M somewhere and in second, simply ssh somewhere. you may see in second terminal:
$ ssh somewhere
+ ssh somewhere
Last login: Mon Feb 3 08:58:01 2014 from elsewhere
If now you hit netstat -tan | grep 192.168.1.31:22 (on any of two oppened ssh session;) you must see that there is only one tcp connection.
This kind of features could be used in combination with -L and maybe some sleep 86399...
To work around a tcp killer router that close every inactive TCP connection from more than 120 seconds, I run:
ssh -M somewhere 'while :;do uptime;sleep 60;done'
This ensure connection stay up even if I dont hit a key for more than two minutes.
Here's a few thoughts that might help.
Sub-shells
Sub-shells fork new processes, but don't return control to the calling shell. If you want to fork a sub-shell to do the work for you, then you'll need to append a & to the line.
(ssh username#domain) &
But this doesn't look like a compelling reason to use a sub-shell. If you had a number commands you wanted to execute in order from each other, yet in parallel from the calling shell, then maybe it would be worth it. For example...
(dothis.sh; thenthis.sh; andthislastthingtoo.sh) &
Forking
I'm not sure why & isn't working for you, but it may be worth looking into nohup as well. This makes the command "immune" to hang up signals.
nohup ssh username#domain (try with and without the & at the end)
Passwords
Not storing passwords in the script is essential for any ssh automation. You can accomplish that using public key cryptography which is an inherent feature of ssh. I wont go into the details here because there are a number of great resources all across the interwebs on setting this up. I strongly suggest investigating this further.
HOWTO: set up ssh keys - Paul Keck, 2001
SSH Keys - archlinux.org
SSH with authentication key instead of password - Debian Administration
Secure Shell - Wikipedia, the free encyclopedia
If you do go this route, I also suggest running ssh in "batch mode" which will disable password querying and will automatically disconnect from the server if it becomes unresponsive after 5 minutes.
ssh -o 'BatchMode=yes' username#domain
Persistence
Then if you want to persist the connection, run some silly loop in bash! :)
ssh -o 'BatchMode=yes' username#domain "while (( 1 == 1 )); do sleep 60; done"
The problem with & is that ssh loses access to its standard input (the terminal), so when it goes to read something to send to the other side it either gets an error and exits, or is killed by the system with SIGTTIN which will implicitly suspend it. The -n and -f options are used to deal with this: -n tells it not to use standard input, -f tells it to set up any necessary tunnels etc., then close the terminal stream.
So the best way to do this is probably to do
ssh -L 9999:localhost:9999 -f host & # for some random unused port
and then manually kill the ssh before logout. Alternately,
ssh -L 9999:localhost:9999 -n host 'while :; do sleep 86400; done' </dev/null &
(The redirection is to make sure the SIGTTIN doesn't happen anyway.)
While you're at it, you may want to save the process ID and shut it down from your .logout/.bash_logout:
ssh -L 9999:localhost:9999 -n host 'while :; do sleep 86400; done' < /dev/null & echo $! >~.ssh_pid; chmod 0600 ~/.ssh_pid
and in .bash_logout:
if test -f ~/.ssh_pid; then
set -- $(sed -n 's/^\([0-9][0-9]*\)$/\1/p' ~/.ssh_pid)
if [ $# = 1 ]; then
kill $1 >/dev/null 2>&1
fi
rm ~/.ssh_pid
fi
The extra code there attempts to avoid someone sabotaging your ~/.ssh_pid, because I'm a professional paranoid.
(Code untested and may have typoes)
It's been a while since I've used ssh, and I can't test it right now, but have you tried the -f switch?
ssh -f username#domain
The man page says it backgrounds ssh. Not sure why & wouldn't work, but I guess it's interpreting it as a command to be run on the remote machine.
Maybe screen + ssh would fit the bill as well?
Something like:
screen -d -m -S sessionName cmd
screen -d -m -S sessionName cmd &
# reconnect with
screen -r sessionName