Directories of the firmware components

Note: Phoenix Contact recommends operating the PLCnext Control device with an SD card if it supports SD card operation. For some PLCnext Control devices, operation with an SD card is mandatory. Refer to the user manual of your PLCnext Control device.

You can access the controller via SFTP or via SSH, view the directories and files in the Linux® file system (on the internal flash memory and on the SD card), and modify them if necessary.

Directories and files that Phoenix Contact provides are stored on the internal flash memory of the controller. If you make changes to the directories or files, the Linux® operating system generates an Overlay File System. It is used to combine contents of a read-only partition with a read-write partition. The read-write partition is stored either at the external SD card or (if no SD card is present) in a dedicated partition of the internal flash memory.

Important directories in the root file system

First generation of PLCnext Control devices

Valid with AXC F 1152, AXC F 2152, AXC F 3152, RFC 4072S, RFC 4072R, EPC 1502, EPC 1522, BPC 9102S

Directory	Contents
/opt/plcnext	Home directory of the `admin` Linux user, all PLCnext users with the `Admin` role, and root directory of the device firmware. Also, files written by the application program are stored in this directory if the specified file name does not contain a storage path.
/opt/plcnext/config	Directory for storing configuration files.
/opt/plcnext/config/System/Um	Directory for storing configuration files of the User Manager. From firmware 2020.6 on, this directory also contains the UmSystemUseNotification.txt (see Default system use notification for details).
/opt/plcnext/logs	Directory for storing the log files of the diagnostic logging as well as the database of the Notification Logger. This directory contains the Output.log files. It contains information on the startup behavior of the firmware, status, and error messages as well as warning notes that help you find the source of error. See Output.log for more information. In addition, you will find the diagnostic log file of the`plcnextapp` command line tools (plcnextapp.log) as well as the log files of the UA server (uatrace.log, uatrace_1.log).
/opt/plcnext/projects	Directory for storing project directories and files
/opt/plcnext/projects/Default	Directory for storing project directories and files downloaded manually by the user
/opt/plcnext/projects/PCWE	Directory for storing PLCnext Engineer projects; PLCnext Engineer exclusively manages all files and subdirectories in this directory. Do not make any changes to this directory.
/opt/plcnext/projects/Splc	Directory for storing SPLC data (safety-related controller)
/opt/plcnext/Security	Directory for storing certificates of `IdentityStores` and `TrustStores`, which are managed by the WBM (from firmware 2025.0 by the WBM 2).
/opt/plcnext/Security/Certificates/https	Directory for storing HTTPS certificates. For more details see WBM: Security - Certificate Authentication or WBM2: Security - Certificate management.
/opt/plcnext/Security/TrustStores/<name>	Directory for storing the Trust Stores. Each subdirectory corresponds to the name of a Trust Store. For more details see WBM Certificate Authentication or WBM2 Certificate management.
/opt/plcnext/Security/TrustStores/Empty	This Trust Store is used by the firmware internally. Do not make any changes to this directory, its subdirectories, or the files in it.
/opt/plcnext/Security/IdentityStores	Directory for storing the Identity Stores. Each subdirectory corresponds to the name of an Identity Store. For more details see WBM Certificate Authentication or WBM 2 Certificate management.
/opt/plcnext/Security/IdentityStores/IDevID	This Identity Store is used by the firmware internally. Do not make any changes to this directory, its subdirectories, or the files in it.
/opt/plcnext/apps	The PLCnext Store manages the directory. Do not make any changes to this directory. All active apps downloaded from the PLCnext Store to the controller are mounted in this directory. Each active app is mounted with the name of the app identifier in a subdirectory. The entire content of the app container is available in this directory (read-only).
/opt/plcnext/installed_apps	Directory for storing all installed app containers. This directory belongs to the PLCnext Store.
/opt/plcnext/appshome	Directory for storing and managing app data. The PLCnext Store and the installed apps manage the directory. Do not make any changes to this directory other than those recommended in the app documentation.
/opt/plcnext/lttng	Directory for storing the default configuration files for tracing via LTTng.
/opt/plcnext/lttng_traces	Directory for storing trace files. The directory is created during runtime of the trace controller when the trigger function for storing the trace files is called for the first time. Each time the trigger function of the memory is called, a new subdirectory (trace directory) for storing the current trace data is created. The designation of a trace directory is structured as follows: `YYYYMMDD_hhmmss`; for example: /opt/plcnext/lttng_traces/20250701_120615/<trace_data> The memory operates as a ring memory. When exceeding the maximum storage space, the oldest trace directory is deleted.
/opt/plcnext/backup	Directory for download changes operations. The directory is used for creating a backup of the project directory (/opt/plcnext/projects/). In the event of an error, the contents of the backup directory are restored. The backup directory is created following the first successful project download and following every successful project download.
/opt/plcnext/data/Services/BackupAndRestore	Directory for storing backups created in the Backup & restore WBM 2 page.
/opt/plcnext/retaining	Directory for storing remanent data.
/opt/plcnext/retaining/backups ≥ 2021.0 LTS	Directory for storing backup files that contain the retain variable values and its corresponding retain CRC along with the project name. Up to 10 backup files are stored before the oldest file is deleted. The criterion is the file name. Find more information about the backup and restore feature in the topic Extended retain handling.
/opt/plcnext/shadowing	Directory for storing shadow copies of C++ user libraries and Shared Object (.so) files related to PLM components.
/usr/local/lib	Directory for storing additional open-source libraries that customized C++ programs use (see C++ programming).
/usr/share/common-licenses	License information on the individual Linux packages of the controller.

Secure-by-default generation of PLCnext Control devices

Valid with Virtual PLCnext Control, AXC F 1252

Note: On Secure-by-default PLCnext Control devices additional folder restrictions can be defined for security reasons - see Access control lists.

Directory	Contents
/home/admin	Home directory of the `admin` Linux user, all PLCnext users with the `Admin` role.
/opt/plcnext/	Root directory of the device firmware. No write permission on this level, see subdirectories in the following rows.
/opt/plcnext/custom	Files written by the application program are stored in this directory if the specified file name does not contain a storage path.
/opt/plcnext/config	Directory for storing configuration files.
/opt/plcnext/config/System/Um	Directory for storing configuration files of the User Manager. From firmware 2020.6 on, this directory also contains the UmSystemUseNotification.txt (see Default system use notification for details).
/opt/plcnext/logs	Directory for storing the log files of the diagnostic logging as well as the database of the Notification Logger. This directory contains the Output.log files. It contains information on the startup behavior of the firmware, status, and error messages as well as warning notes that help you find the source of error. See Output.log for more information. In addition, you will find the diagnostic log file of the`plcnextapp` command line tools (plcnextapp.log) as well as the log files of the UA server (uatrace.log, uatrace_1.log).
/opt/plcnext/projects	Directory for storing project directories and files
/opt/plcnext/projects/Default	Directory for storing project directories and files downloaded manually by the user
/opt/plcnext/projects/PCWE	Directory for storing PLCnext Engineer projects; PLCnext Engineer exclusively manages all files and subdirectories in this directory. Do not make any changes to this directory.
/opt/plcnext/projects/Splc	Directory for storing SPLC data (safety-related controller)
/opt/plcnext/config/System/Security	Directory for storing certificates of `IdentityStores` and `TrustStores`, which are managed by the WBM (from firmware 2025.0 by the WBM 2).
/opt/plcnext/config/System/Security/Certificates/https	Directory for storing HTTPS certificates. For more details see WBM: Security - Certificate Authentication or WBM2: Security - Certificate management.
/opt/plcnext/config/System/Security/TrustStores/<name>	Directory for storing the Trust Stores. Each subdirectory corresponds to the name of a Trust Store. For more details see WBM Certificate Authentication or WBM2 Certificate management.
/opt/plcnext/config/System/Security/TrustStores/Empty	This Trust Store is used by the firmware internally. Do not make any changes to this directory, its subdirectories, or the files in it.
/opt/plcnext/config/System/Security/IdentityStores/<name>	Directory for storing the Identity Stores. Each subdirectory corresponds to the name of an Identity Store. For more details see WBM Certificate Authentication or WBM 2 Certificate management.
/opt/plcnext/config/System/Security/IdentityStores/IDevID	This Identity Store is used by the firmware internally. Do not make any changes to this directory, its subdirectories, or the files in it.
/opt/plcnext/apps/mounted	The PLCnext Store manages the directory. Do not make any changes to this directory. All active apps downloaded from the PLCnext Store to the controller are mounted in this directory. Each active app is mounted with the name of the app identifier in a subdirectory. The entire content of the app container is available in this directory (read-only).
/opt/plcnext/apps/installed	Directory for storing all installed app containers. This directory belongs to the PLCnext Store.
/opt/plcnext/appshome	Directory for storing and managing app data. The PLCnext Store and the installed apps manage the directory. Do not make any changes to this directory other than those recommended in the app documentation.
/opt/plcnext/config/Services/TraceController	Directory for storing the default configuration files for tracing via LTTng.
/opt/plcnext/lttng_traces	Directory for storing trace files. The directory is created during runtime of the trace controller when the trigger function for storing the trace files is called for the first time. Each time the trigger function of the memory is called, a new subdirectory (trace directory) for storing the current trace data is created. The designation of a trace directory is structured as follows: `YYYYMMDD_hhmmss`; for example: /opt/plcnext/lttng_traces/20250701_120615/<trace_data> The memory operates as a ring memory. When exceeding the maximum storage space, the oldest trace directory is deleted.
/opt/plcnext/data/Plc/Backup/backup	Directory for download changes operations. The directory is used for creating a backup of the project directory (/opt/plcnext/projects/). In the event of an error, the contents of the backup directory are restored. The backup directory is created following the first successful project download and following every successful project download.
/opt/plcnext/data/Services/BackupAndRestore	Directory for storing backups created in the Backup & restore WBM 2 page.
/opt/plcnext/data/Plc/Retain/retaining	Directory for storing remanent data.
/opt/plcnext/data/Plc/Retain/retaining/backups	Directory for storing backup files that contain the retain variable values and its corresponding retain CRC along with the project name. Up to 10 backup files are stored before the oldest file is deleted. The criterion is the file name. Find more information about the backup and restore feature in the topic Extended retain handling.
/opt/plcnext/data/Plc/Plm/shadowing	Directory for storing shadow copies of C++ user libraries and Shared Object (.so) files related to PLM components.
/usr/local/lib	Directory for storing additional open-source libraries that customized C++ programs use (see C++ programming).
/usr/share/common-licenses	License information on the individual Linux packages of the controller.

Directories of the firmware components

Important directories in the root file system

First generation of PLCnext Control devices

Secure-by-default generation of PLCnext Control devices

First generation of PLCnext Control devices

Secure-by-default generation of PLCnext Control devices