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, wait a couple of minutes and run:

systemctl is-active jdownloader

If the result is:

active

no further action is required.

If the result is not active, check:

ls -lh /opt/jdownloader/JDownloader.jar /opt/jdownloader/Core.jar
sudo systemctl status jdownloader --no-pager

If JDownloader.jar is missing, do not reinstall JDownloader or replace /opt/jdownloader/cfg. Investigate the update failure first.