How to run a script, depending on internet connection

Question

I often mount a remote drive using sshfs. I would love to have this mount automatically. However, if I mount it in my .bashrc or startup scripts, the mount often fails because my wireless internet connection has not yet been made.

Does anybody know of an easy way to execute a bash scrip every time the connection is made, or to auto-mount an sshfs drive?

Answer 1

Add your script to /etc/network/if-up.d/. Name your script without a '.sh' extension.

Also after adding script run chmod +x /etc/network/if-up.d/yourscriptname to give necessary permission.

Make sure the network interface (e.g. wlan0 or eth0) that should trigger your script when turned on is mentioned in the file /etc/network/interfaces.

Answer 2

Editor's note: Cuttlefish hasn't been updated since 2012 and is not in any current Ubuntu repositories

Ubuntu 12.04

• Install Cuttlefish: A simple tool, which realises reflexes on your computer by executing actions when specific events are triggered.

• Open Cuttlefish and click on New.

  

  • Give it a name, and change Activated by stimulus option to ON.
  • Click on Stimulus, select the category Network and type Connect to WLAN. Click OK.

  

  • You can also select the SSID of wireless network and you have an option of whether or not to check this on startup.

  

  • Now you will have to specify a reaction. Go to Reaction tab, and click add. Select Applications from the category and Start Application (in advanced mode) from type.

  

  • Now specify the script which you want to run in executable option. You can even pass parameters to the script.

  

  • And that's it! Also make sure that you add Cuttlefish in startup applications. Go to Edit > Preferences and enable the autostart option.

  

Answer 3

As far as I'm concerned, the /etc/network/if-up.d/ solution did not work from me as when I added to /etc/network/interfaces the following:

auto wlp58s0
iface wlp58s0 inet dhcp
post-up /home/augustin/Config/myscript.sh

Wifi would start after reboot.

But after some struggle, from this link, what worked was to add the script to /etc/NetworkManager/dispatcher.d/ in the form 90myscript.sh where 90 is the priority level of the script and with the following form:

#!/bin/bash
IF=$1
STATUS=$2
if [ "$IF" == "wlp58s0" ]
then
    case "$2" in
        up)
        # interface is up
        ;;
        down)
        # interface will be down
        ;;
        pre-up)
        # interface will be up
        ;;
        post-down)
        # interface is down
        ;;
        *)
        ;;
    esac
fi

I guess there are issues between who controls the network config at system level and sometimes the default network behavior is left behind the dispatcher one.

Also, for those who would like - like me - to try to have a symbolic link to the script (to store the file in a better location), unfortunately it did not work for me.

Hope this helps!

Answer 4

I will answer this part of the OP question: "I would love to have this mount automatically"

My favorite tool for automounting network shares is autofs: https://help.ubuntu.com/community/Autofs

AutoFS is my tool of choice to mount my NAS - for all my laptops and workstations.

"autofs is a program for automatically mounting directories on an as-needed basis. Auto-mounts are mounted only as they are accessed, and are unmounted after a period of inactivity. Because of this, automounting NFS/Samba shares conserves bandwidth and offers better overall performance compared to static mounts via fstab."

Answer 5

systemd seems to have taken over networking nowadays.

$ networkctl
WARNING: systemd-networkd is not running, output will be incomplete.

IDX LINK             TYPE               OPERATIONAL SETUP
  1 lo               loopback           n/a         unmanaged
  2 enp0s25          ether              n/a         unmanaged
  3 wlo1             wlan               n/a         unmanaged

3 links listed.

It also has units corresponding to the interfaces

$ systemctl list-units |grep wlo1
sys-devices-pci0000:00-0000:00:1c.3-0000:24:00.0-net-wlo1.device                                                        loaded active plugged   Centrino Ultimate-N 6300 (3x3 AGN)
sys-subsystem-net-devices-wlo1.device                                                                                   loaded active plugged   Centrino Ultimate-N 6300 (3x3 AGN)

Apparently you can use these in service unit files. So just create a service unit to run your script and use something like that inside to make it run conditionally on the network:

BindsTo=sys-subsystem-net-devices-wlo1.device
After=sys-subsystem-net-devices-wlo1.device

Good luck! I haven't tested this, so "your mileage may vary".

Sources:

• https://unix.stackexchange.com/questions/126009/cause-a-script-to-execute-after-networking-has-started
• https://unix.stackexchange.com/questions/257888/systemd-wait-for-network-interface-to-be-up-before-running-service

Answer 6

The best, simple and easy way would be to add an up command to what ever interface on which you want work on.

Interfaces can be found in the "/etc/network/" directory under the file name "interfaces"

iface elan0 inet manual
    up filename.sh

This will add the up command to elan0. Simillarly give this to what ever interface you want to work on. Remember to indent one tab space.

Make sure you give the execute permissions to the file.

sudo chmod 755 filename.sh