Linux SystemD Path

Sending files to a remote SFTP immediately

In modern Linux systems there’s SystemD path unit. It allows you to monitor specific directory and trigger connect tool to automatically transmit data.

Let’s say we’d like to send all .zip files from /data folder to target folder of SFTP server 10.0.0.24 using monitor02 user and id_ed25519 key that is password protected.

Moreover we’d like those files to be send automatically as soon as they appear in the /data folder.

1. First we need to test the connection

$ connect test sftp -h 10.0.0.24 -l monitor02 -i /apps/keys/id_ed25519 -k -
2025/02/10 09:13:31 INFO License valid to: 2026-04-13 18:06:28
2025/02/10 09:13:31 INFO Licensed for: Ultimate
Enter Private Key Passphrase:
2025/02/10 09:13:33 INFO Testing connection to sftp://[email protected]
The key of 10.0.0.24:22 is unknown. Do you want to add this key to known_hosts (y/n): y
2025/02/10 09:13:39 INFO Connection successful

Note

Upon first connection we’ll be asked to add the remote server host key to known_hosts file.

2. Then we need to store the key password in a file and rerun the connection test

$ echo "pass" > /apps/send_pass
$ connect test sftp -h 10.0.0.24 -l monitor02 -i /apps/keys/id_ed25519 --identity-passphrase-file /apps/send_pass
2025/02/10 09:15:49 INFO License valid to: 2026-04-13 18:06:28
2025/02/10 09:15:49 INFO Licensed for: Ultimate
2025/02/10 09:15:49 INFO Testing connection to sftp://[email protected]
2025/02/10 09:15:50 INFO Connection successful
$ cat /apps/send_pass
ENC:QqKtxb2TeNoXXUIV7P64wJXy07tM33er9PPNcNozhz5lPg==

Note

Upon first use key password got encrypted.

3. Then we need to prepare the connect sftp send command

$ connect send sftp \
                     -h 10.0.0.24 \
                     -l monitor02 \
                     -i /apps/keys/id_ed25519 \
                     --identity-passphrase-file /apps/send_pass \
                     -s /data \
                     --file-mask "*.zip" \
                     -d target \
                     --delete \
                     --parallel 3 \
                     --batch \
                     --no-color
2025/02/10 09:36:44 INFO License valid to: 2026-04-13 18:06:28
2025/02/10 09:36:44 INFO Licensed for: Ultimate
2025/02/10 09:36:44 INFO Sending files to sftp://[email protected]:target
2025/02/10 09:36:47 INFO created directory name=target
2025/02/10 09:36:47 INFO Transferring file=/data/file1.zip sftpSessionID=2 targetFolder=target
2025/02/10 09:36:48 INFO Transferring file=/data/file3.zip sftpSessionID=1 targetFolder=target
2025/02/10 09:36:48 INFO Transferring file=/data/file2.zip sftpSessionID=3 targetFolder=target
2025/02/10 09:36:48 INFO File deleted file=/data/file1.zip sftpSessionID=2
2025/02/10 09:36:48 INFO File transferred successfully bytesTransferred=10485760 duration=912ms transferRate=10.96MB/s file=/data/file1.zip sftpSessionID=2 targetFolder=target
2025/02/10 09:36:49 INFO File deleted file=/data/file2.zip sftpSessionID=3
2025/02/10 09:36:49 INFO File transferred successfully bytesTransferred=10485760 duration=876ms transferRate=11.41MB/s file=/data/file2.zip sftpSessionID=3 targetFolder=target
2025/02/10 09:36:49 INFO File deleted file=/data/file3.zip sftpSessionID=1
2025/02/10 09:36:49 INFO File transferred successfully bytesTransferred=10485760 duration=882ms transferRate=11.33MB/s file=/data/file3.zip sftpSessionID=1 targetFolder=target
2025/02/10 09:36:49 INFO Disconnected sftpSessionID=2 target=sftp://[email protected]:
2025/02/10 09:36:49 INFO Disconnected sftpSessionID=3 target=sftp://[email protected]:
2025/02/10 09:36:49 INFO Disconnected sftpSessionID=1 target=sftp://[email protected]:

Parameters

-h 10.0.0.24 IP address of the target SFTP server
-l monitor02 SFTP user name on the target server
-i /apps/keys/id_ed25519 SSH private key
--identity-passphrase-file /apps/send_pass file containing private key password
-s /data source folder containing the files to send
--file-mask "*.zip" file mask for the files to send
-d target target folder on the remote SFTP server
--delete we want to delete files after successful transmission
--parallel 3 we want to send files using 3 parallel sessions
--batch we want to progress bar
--no-color disables colored output

4. Prepare sending service

$ systemctl --user edit --force --full send.service
[Unit]
Description=SFTP Send Service
After=network-online.target
Wants=network-online.target

[Service]
ExecStart=/apps/connect send sftp -h 10.0.0.24 -l monitor02 --password-file /apps/send_pass -s /data --file-mask "*.zip" -d target --delete --parallel 3 --batch --no-color

Note

If you receive following error:

Failed to connect to bus: No medium found

Then please login to the account directly ssh myaccount@myhost and not via su - myaccount

Reload systemd, start the service one time and check the logs.

$ systemctl --user daemon-reload
$ systemctl --user start send
$ journalctl --user -eu send
Feb 10 10:11:37 arm systemd[1270]: Started send.service - SFTP Send Service.
Feb 10 10:11:37 arm connect[4036]: 2025/02/10 10:11:37 INFO License valid to: 2026-04-13 18:06:28
Feb 10 10:11:37 arm connect[4036]: 2025/02/10 10:11:37 INFO Licensed for: Ultimate
Feb 10 10:11:37 arm connect[4036]: 2025/02/10 10:11:37 INFO Sending files to sftp://[email protected]:target
Feb 10 10:11:37 arm connect[4036]: 2025/02/10 10:11:37 WARN No file to send

5. Prepare SystemD Path unit

$ systemctl --user edit --force --full send.path
[Unit]
After=network.target

[Path]
PathModified=/data
Unit=send.service

[Install]
WantedBy=multi-user.target

Tip

PathModified specifies the directory to watch for new files. It should match the -s /data parameter in the connect tool.

6. Enable SystemD Path unit

$ systemctl --user daemon-reload
$ systemctl --user --now enable send.path
Created symlink /apps/.config/systemd/user/default.target.wants/send.path → /apps/.config/systemd/user/send.path.

7. Allow a user’s systemd services to run even after the user has logged out.

$ sudo loginctl enable-linger $(whoami)

Note

This step requires elevated privileges.

8. Check the job logs

$  journalctl --user -eu send
Feb 10 10:54:34 arm systemd[1270]: Started send.service - SFTP Send Service.
Feb 10 10:54:35 arm connect[5750]: 2025/02/10 10:54:35 INFO License valid to: 2026-04-13 18:06:28
Feb 10 10:54:35 arm connect[5750]: 2025/02/10 10:54:35 INFO Licensed for: Ultimate
Feb 10 10:54:35 arm connect[5750]: 2025/02/10 10:54:35 INFO Sending files to sftp://[email protected]:target
Feb 10 10:54:37 arm connect[5750]: 2025/02/10 10:54:37 INFO Transferring file=/data/test1.zip sftpSessionID=1 targetFolder=target
Feb 10 10:54:42 arm connect[5750]: 2025/02/10 10:54:42 INFO File deleted file=/data/test1.zip sftpSessionID=1
Feb 10 10:54:42 arm connect[5750]: 2025/02/10 10:54:42 INFO File transferred successfully bytesTransferred=104857600 duration=5s484ms transferRate=18.23MB/s file=/data/test1.zip sftpSessionID=1 targetFolder=target