Execute script after a network connection has been established

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1

Hello kind people,

I recently bought a used HP ProBook 6460b in order to convert it into a machine to do some coding. I installed the latest Manjaro XFCE Edition on it.

In order to make my life easier, i wanted to get manjaro to mount my network share automatically, but only when im at home.

so i did the following

create an .smbcredentials file
create a target folder in /mnt
test a command to mount the drive in the target folder
move .smbcredentials to / and change ownership to root
chmod 600 . smbcredentials
test the mount command again.

until this point, no problem.
in order to check if i am home or not and than mount the drive, i created the following script

/usr/local/bin/fritzmount.sh

#!/bin/bash

sleep 30s
if [[ $(/usr/bin/arping -c 1 192.168.178.1|cgrep -i  --color --no-numbers "F0:B0:XX:XX:XX:XX") ]]; then
	mount -t cifs -o credentials=/.smbcredentials,vers=1.0,noserverino //192.168.178.1/FRITZ.NAS/Nas/user /mnt/fritznas/
else
echo "not found"
fi

and that script seems to work too

i finally created a .service file with the following content

[Unit]
# Type=simple|forking|oneshot|dbus|notify|idle
Description=Automount for Fritz Nas
## make sure we only start the service after network is up
Wants=network-online.target
After=network.target

[Service]
## here we can set custom environment variables
Type=oneshot
User=root
WorkingDirectory=/usr/local/bin
ExecStart=fritzmount.sh
StandardOutput=append:/mount.log
StandardError=append:/mounterror.log
# don't use 'nobody' if your script needs to access user files
# (if User is not set the service will run as root)
#User=nobody

# Useful during debugging; remove it once the service is working
#StandardOutput=console

[Install]
WantedBy=multi-user.target

and ran
sudo systemd-analyze verify automount_fritzbox.service
wich passed without problems

sudo systemctl daemon-reload
sudo systemctl enable automount_fritzbox.service

However, after restarting the pc, the drive was not mounted.
No matter where i look, i cant seem to figure out why and as such i turn to you for insight.

Thanks you,
Sulumar

2

Not good. Do not do this. Get rid of Working directory and use the absolute path in ExecStart.

Also check the journal.

journalctl -u automount_fritzbox.service
3

Is this really nessesay? Why not put it in the journal with all the other messages from this unit?

4

Is this really nessesay? Why not put it in the journal with all the other messages from this unit?

Because i have no idea how. at least this way i knew where the logs went
I will try editing the .service file according to your suggestion.

If you dont mind, would you tell me why using Working Dir is not good ?

5

Because it does not change the directory before ExecStart is executed. It changes the directory after that.

It basically does a cd /path after the script is started, but before the first command from the script is executed.

However, use always a full path to the script or binary in ExecStart.

6

Heres the journal output, looks like the script got executed

↪ journalctl -u automount_fritzbox.service                                                                                                     14:06:31
-- Journal begins at Thu 2021-01-14 20:31:50 CET, ends at Wed 2021-01-20 14:07:44 CET. --
Jan 18 19:13:08 jerome-devstation systemd[1]: /etc/systemd/system/automount_fritzbox.service:21: Failed to parse output specifier, ignoring: console
Jan 18 19:17:14 jerome-devstation systemd[1]: /etc/systemd/system/automount_fritzbox.service:22: Failed to parse output specifier, ignoring: console
-- Boot 7eaa771c1b294e0b8ea17e04d8cc9a57 --
Jan 18 19:22:37 jerome-devstation systemd[1]: Starting Automount for Fritz Nas...
Jan 18 19:22:50 jerome-devstation systemd[1]: automount_fritzbox.service: Succeeded.
Jan 18 19:22:50 jerome-devstation systemd[1]: Finished Automount for Fritz Nas.
Jan 18 19:26:25 jerome-devstation systemd[1]: Starting Automount for Fritz Nas...
Jan 18 19:26:27 jerome-devstation systemd[1]: automount_fritzbox.service: Succeeded.
Jan 18 19:26:27 jerome-devstation systemd[1]: Finished Automount for Fritz Nas.
Jan 18 19:30:40 jerome-devstation systemd[1]: /etc/systemd/system/automount_fritzbox.service:22: Failed to parse output specifier, ignoring: console
-- Boot 7978e997ddc14c10a4f9a4033a07ef82 --
Jan 18 19:37:41 jerome-devstation systemd[1]: Starting Automount for Fritz Nas...
Jan 18 19:38:37 jerome-devstation systemd[1]: automount_fritzbox.service: Succeeded.
Jan 18 19:38:37 jerome-devstation systemd[1]: Finished Automount for Fritz Nas.
-- Boot 2bc140dad13549b184c78ddab9484299 --
Jan 18 19:43:38 jerome-devstation systemd[1]: Starting Automount for Fritz Nas...
Jan 18 19:44:32 jerome-devstation systemd[1]: automount_fritzbox.service: Succeeded.
Jan 18 19:44:32 jerome-devstation systemd[1]: Finished Automount for Fritz Nas.
Jan 18 19:50:40 jerome-devstation systemd[1]: Starting Automount for Fritz Nas...
Jan 18 19:51:12 jerome-devstation systemd[1]: automount_fritzbox.service: Succeeded.
Jan 18 19:51:12 jerome-devstation systemd[1]: Finished Automount for Fritz Nas.
-- Boot 10d9edff1477428b8cb63c140e2e5a36 --
Jan 20 11:38:40 jerome-devstation systemd[1]: Starting Automount for Fritz Nas...
Jan 20 11:39:17 jerome-devstation systemd[1]: automount_fritzbox.service: Succeeded.
Jan 20 11:39:17 jerome-devstation systemd[1]: Finished Automount for Fritz Nas.
-- Boot 92e6e0eacef4449bbcff089ab876e7a4 --
Jan 20 13:35:44 jerome-devstation systemd[1]: Starting Automount for Fritz Nas...
Jan 20 14:01:36 jerome-devstation systemd[1]: automount_fritzbox.service: Succeeded.
Jan 20 14:01:36 jerome-devstation systemd[1]: Finished Automount for Fritz Nas.
sulumar at jerome-devstation in /m/fritznas
↪

however, ls -la

[sulumar@jerome-devstation]
[14:11:36 fritznas]$ ls -la
insgesamt 8,0K
drwxr-xr-x 2 root root 4,0K 18. Jan 19:45 .
drwxr-xr-x 3 root root 4,0K 18. Jan 19:45 ..

it seems its still not mounted

i checked the mounterror.log and found this

↪ cat mounterror.log                                                                                                                           
/usr/bin/arping: NETLINK_ROUTE unexpected iov element
/usr/bin/arping: NETLINK_ROUTE unexpected iov element
/usr/bin/arping: NETLINK_ROUTE unexpected iov element
/usr/bin/arping: NETLINK_ROUTE unexpected iov element
7

looks like as of the ping command doesn’t work.

8

my best guess is the arping goes off before the wifi connection is established
i tried to get the script to check by pinging the router and waiting for a reply but i cant get the bash script to work propperly.

Hell, it cant be that difficult to check for a working network connection. i must be missing something.
Here is the bash script i wrote, but that wont even run manually
throws out
.> /fritzmount.sh: Zeile 3: [: syntax error: `-q’ unexpected

./fritzmount.sh: Zeile 3: 20: Datei oder Verzeichnis nicht gefunden
./fritzmount.sh: Zeile 9: [: Fehlende »]«

before proceeding to try and mount the drive, if connected
if not connected or not on my home network it pings indefinitely

i=0
while [ ! ping -q -c 1 -W 1 192.168.178.1 >> /dev/null ] || [ i < 20 ]; do
	let "i = i+1"
	sleep 1
	
done

if [ i >= 20]; then
	echo "Network Down"
else

	if [[ $(/usr/bin/arping -c 1 192.168.178.1|cgrep -i --no-numbers "F0:B0:14:57:E5:21") ]]; then
		mount -t cifs -o credentials=/.smbcredentials,vers=1.0,noserverino //192.168.178.1/FRITZ.NAS/Nas/Jerome /mnt/fritznas/
	else
		echo "not home"
	fi
fi

you’d think that after coding some C, some java and some python, id grasp bash but obviously not

9

Well, maybe it is easier to use NM dispatcher. It can start scripts (as root) after a connection is established.

https://wiki.archlinux.org/index.php/NetworkManager#Mounting_of_SMB_shares

If you go with the systemd stuff, add Requires=network-online.target and make sure it is set.

Also check first if the wifi devices has an IP (if possible check for a specific IP). Only then start pining.