Can aria2 periodically save its session state?

The popular command-line download utility aria2 can automatically and periodically save its active download session state to a designated file. This capability prevents the loss of your download progress in the event of an unexpected system crash, power outage, or ungraceful application shutdown. Managing this behavior relies on defining a target text file to hold the data and choosing the frequency at which the state information is written to the disk.

Understanding the Configuration Parameters

To successfully implement periodic session saving, aria2 requires two baseline options alongside the specific interval configuration parameter. If the software does not know where to record the state, the interval configuration will have no effect.

• --save-session: This parameter requires a string value pointing to the file path where you want aria2 to keep its session records (e.g., /path/to/session.txt).
• --input-file: To ensure your session resumes after a system restart, you should also point this parameter to the exact same text file. Aria2 reads this file at startup to reload incomplete downloads.

Configuring the Time Interval

The exact parameter used to dictate how often aria2 flushes its current state to the specified file is --save-session-interval.

The Default Behavior

By default, if you specify a --save-session path but omit the interval parameter, aria2 sets the value to 0. A value of 0 means the program will only save the session file when it shuts down cleanly and gracefully (such as receiving a SIGINT or SIGTERM signal, or pressing Ctrl+C in the terminal). It will not write periodic backups during the download process.

Changing the Frequency

To set a continuous backup routine, pass an integer value greater than zero representing time measured in seconds. For example, if you want your download lists and active tasks serialized to disk every 60 seconds, you can supply the following flag in your terminal:

aria2c --save-session=/path/to/session.txt --save-session-interval=60

Implementing Settings via Configuration File

If you run aria2 constantly as a background daemon or via an RPC interface, adding command-line parameters every time can become tedious. Instead, you can save these directives directly into your permanent configuration file (typically named aria2.conf).

# Enable session tracking
save-session=/path/to/session.txt
input-file=/path/to/session.txt

# Automatically flush progress to disk every 2 minutes
save-session-interval=120

Setting a shorter time frame ensures that minimal progress is lost if the application terminates abruptly. However, choosing an excessively frequent interval (such as every few seconds) on slower storage media could cause unnecessary disk write cycles. A duration between 30 and 120 seconds balances safety and disk performance for most systems.