IT Forensics · Linux

Forensic analysis of init.d scripts – Checking traditional system boot mechanisms

init.d scripts are part of the traditional SysV init system, which has been replaced by systemd in many modern distributions; however, for compatibility reasons, they are often still supported or used in part.

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As init.d scripts are standard executable shell scripts, they offer a relatively simple way of running programmes automatically at system start-up, which is why they are also checked for persistence mechanisms.

Why LanCologne?

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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We identify existing init.d scripts and their links in the respective runlevel directories, check the script content for any suspicious commands, and map these to the system boot behaviour.

Typical areas of application

Investigation of older or hybrid Init configurations
Identifying persistence mechanisms via traditional start scripts
Analysis of compatibility layers between SysV-Init and systemd
Reconstruction of the historical system boot behaviour
Incident Response on Linux Systems
Judicial and non-judicial expert reports

This is how an init.d analysis works

Once the backup has been completed, any existing init.d scripts and their links in the runlevel directories are recorded. The contents of each script are checked for unusual or atypical commands and compared with known standard scripts for the respective distribution.

Why is the init.d analysis relevant from a forensic perspective?

Even on systems that primarily use systemd for boot, init.d compatibility mechanisms may still be active, thereby representing an additional, easily overlooked means of persistence.

Older systems or migrated systems, in particular, may contain init.d configurations that have evolved over time, the forensic relevance of which must be assessed separately.

Frequently Asked Questions

Are init.d scripts still used on modern systems?+
In many cases, this is still supported for compatibility reasons, even though systemd is the primary init system.
Where are the init.d scripts located?+
Typically in a central script directory, with corresponding shortcuts in the respective runlevel directories.
Can init.d scripts be misused for persistence?+
Yes, as these are standard executable shell scripts, they can be misused for automated execution in a similar way to systemd units.

LanCologne – Linux Forensics Cologne

Do you require a professional forensic investigation into „forensic analysis of init.d scripts"? LanCologne can assist you with the legally admissible preservation of digital evidence and the transparent analysis of relevant Linux artefacts.

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