IT Forensics · Linux

Forensic classification of tmpfs and RAM-based file systems – Correctly assessing volatile memory areas

tmpfs and similar RAM-based file systems store data exclusively in main memory in order to speed up access. They are frequently used in Linux for temporary directories such as /tmp or /run.

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As tmpfs contents are not, by design, stored persistently, they are lost when the system is shut down or restarted. For forensic analysis, it is therefore often necessary to take a live backup of the system memory whilst the system is still running.

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Since its foundation, LanCologne has specialised in professional IT forensics. Our staff have decades of experience in the field of information technology and assist companies, solicitors, private individuals and, on a regular basis, the courts in the technical investigation of complex digital matters.

The examination is, as a matter of principle, carried out exclusively on a forensic copy, a forensic image or a data source captured in a technically equivalent manner that preserves the integrity of the evidence. The original evidence remains unchanged and is stored in a manner that preserves its integrity.

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For systems that are currently running, we examine which forensically relevant data is contained in tmpfs-based directories and back this up as part of a live data collection process, provided that this is technically feasible and has been agreed with the client.

Typical areas of application

•Backing up temporary data whilst systems are running
•Investigation of applications using temporary working directories
•Evaluation of container-based tmpfs mounts
•Recovering files that appear to have disappeared after a restart
•Incident Response on Linux Systems
•Judicial and non-judicial expert reports

This is how the categorisation of tmpfs content works

For a system that is still running, the first step is to check which tmpfs mounts are present and what data they contain. Where technically feasible, relevant areas are backed up as part of a live capture, whilst documenting the unavoidable changes in system state that occur during this process. For systems that have already been shut down, the loss of this data is explained in a technically verifiable manner.

Why is the classification of tmpfs relevant from a forensic perspective?

Many applications and containers use tmpfs for temporary working data, which may be relevant to forensic analysis but is irretrievably lost after a reboot. Understanding this correctly prevents false expectations regarding the recoverability of such data.

If a system is shut down before a backup is taken, any data stored on it may be lost permanently. This underlines the importance of an early, expert assessment.

Frequently Asked Questions

Is tmpfs data retained after a reboot?+
No, tmpfs contents are stored exclusively in main memory and are always lost when the system is shut down or restarted.
Can tmpfs be read retrospectively?+
Once the system has been restarted, this is usually no longer possible. A backup can only be made whilst the system is still running.
Do containers frequently use tmpfs?+
Yes, tmpfs mounts are often used for temporary working directories in containers, such as for caches or session data.

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