JDownloader runs directly on Ubuntu as a systemd service. It is not a Docker container.
Permanent installation directory:
/opt/jdownloader
Systemd service:
jdownloader.service
The established JDownloader configuration is stored under:
/opt/jdownloader/cfg
It is okay to initiate a JDownloader update through MyJDownloader / the web interface.
JDownloader may stop and restart itself while applying an update. Give it a couple of minutes to complete before intervening.
After an update, verify that the service came back:
systemctl is-active jdownloader
Normal result:
active
For more detail:
sudo systemctl status jdownloader --no-pager
The running process can also be checked with:
pgrep -af 'java.*JDownloader'
A healthy installation should show Java running:
/opt/jdownloader/JDownloader.jar
For example:
/usr/bin/java -Djava.awt.headless=true -jar /opt/jdownloader/JDownloader.jar
Start JDownloader:
sudo systemctl start jdownloader
Stop JDownloader:
sudo systemctl stop jdownloader
Restart JDownloader:
sudo systemctl restart jdownloader
Check whether it is running:
systemctl is-active jdownloader
Detailed status:
sudo systemctl status jdownloader --no-pager
First check its status:
sudo systemctl status jdownloader --no-pager
If the service is simply stopped, try starting it:
sudo systemctl start jdownloader
Then verify:
systemctl is-active jdownloader
If the service fails again, do not immediately reinstall JDownloader, delete files, or replace the configuration.
Check that the main application files still exist:
ls -lh /opt/jdownloader/JDownloader.jar /opt/jdownloader/Core.jar
Check whether another JDownloader Java process is already running:
pgrep -af 'java.*JDownloader'
If JDownloader.jar is missing or the service still will not start, stop here and investigate the updater logs before changing the installation.
The established JDownloader configuration is stored under:
/opt/jdownloader/cfg
This directory contains the settings used by the established installation.
Preserve this directory during troubleshooting or recovery.
Do not replace it with the configuration from a newly created or temporary JDownloader installation.
During an update failure, troubleshooting, or recovery, another JDownloader installation may appear under:
/home/mike/.jd_home
Do not assume this is the permanent installation.
The systemd-managed installation is:
/opt/jdownloader
A .jd_home installation may contain newly downloaded JDownloader application files while having a new or default configuration.
In particular, do not replace:
/opt/jdownloader/cfg
with:
/home/mike/.jd_home/cfg
unless there is a specific, verified reason to do so.
The presence of newer JDownloader.jar or Core.jar files under .jd_home does not by itself mean that JDownloader should be moved there.
Show the most recent systemd log entries:
journalctl -u jdownloader -n 100 --no-pager
Follow the service log live:
journalctl -u jdownloader -f
Press Ctrl+C to stop following the log.
JDownloader's own logs are stored under:
/opt/jdownloader/logs
These logs can be useful when diagnosing an update or restart failure.
On September 21, 2026, an update initiated through JDownloader resulted in the service becoming unavailable.
Investigation established that JDownloader was operating from the correct installation:
/opt/jdownloader
At approximately 13:28, JDownloader deliberately initiated its normal update/restart process and launched itself with:
JDownloader.jar -forceupdate
The updater continued to operate against the correct /opt/jdownloader installation.
Its updater self-test used:
/opt/jdownloader/tmp/update/self/JDU/JDownloader.jar
and reported:
Validate: OK SelfTest Results: OK Self Update successful
JDownloader subsequently performed a normal shutdown. At 13:31:59, systemd recorded:
jdownloader.service: Deactivated successfully.
However, by the next attempt to start the service at 13:32:55:
/opt/jdownloader/JDownloader.jar
was no longer available.
Systemd therefore reported:
Error: Unable to access jarfile /opt/jdownloader/JDownloader.jar
and subsequent automatic restart attempts failed for the same reason.
The exact reason the updater failed to leave a usable replacement JDownloader.jar in /opt/jdownloader was not established.
The investigation did not find evidence that initiating the update through MyJDownloader was incorrect, nor did it establish systemd's Restart=on-failure setting as the cause.
A separate fresh JDownloader installation was discovered under:
/home/mike/.jd_home
It contained newer application files, but its cfg directory contained only a small/default configuration.
The established configuration under:
/opt/jdownloader/cfg
was therefore preserved.
For this specific recovery, fresh copies of JDownloader.jar and Core.jar were restored to /opt/jdownloader while retaining the existing cfg directory.
After recovery:
systemctl is-active jdownloader
returned:
active
and the running Java process again used:
/opt/jdownloader/JDownloader.jar
MyJDownloader also reconnected using the existing configuration.
Important: Copying application files from .jd_home was an incident-specific recovery procedure. It should not be treated as the normal JDownloader update procedure.
After initiating a JDownloader update or restart, wait a couple of minutes and run:
systemctl is-active jdownloader ls -lh /opt/jdownloader/JDownloader.jar cat /opt/jdownloader/JDownloader.pid pgrep -af 'java.*JDownloader'
Normal results should show:
* jdownloader is active
* /opt/jdownloader/JDownloader.jar exists
* JDownloader.pid contains a process ID
* the same process ID is running Java with /opt/jdownloader/JDownloader.jar
If JDownloader.jar is missing, do not repeatedly restart the service, reinstall JDownloader, or replace /opt/jdownloader/cfg.
Stop the service first:
sudo systemctl stop jdownloader
Then investigate the updater state before restoring any files.