systemd-coredump

systemd
Developer Lennart Poettering lennart@poettering.net
systemd-coredump 8
systemd-coredump systemd-coredump.socket systemd-coredump@.service Acquire, save and process core dumps

`/usr/lib/systemd/systemd-coredump`

`/usr/lib/systemd/systemd-coredump` `--backtrace`

`systemd-coredump@.service`

`systemd-coredump.socket`

## Description

`systemd-coredump@.service` is a system service that can acquire core dumps from the kernel and handle them in various ways. The `systemd-coredump` executable does the actual work. It is invoked twice: once as the handler by the kernel, and the second time in the `systemd-coredump@.service` to actually write the data to the journal.

When the kernel invokes `systemd-coredump` to handle a core dump, it runs in privileged mode, and will connect to the socket created by the `systemd-coredump.socket` unit, which in turn will spawn an unprivileged `systemd-coredump@.service` instance to process the core dump. Hence `systemd-coredump.socket` and `systemd-coredump@.service` are helper units which do the actual processing of core dumps and are subject to normal service management.

Core dumps can be written to the journal or saved as a file. Once saved they can be retrieved for further processing, for example in gdb 1.

By default, `systemd-coredump` will log the core dump including a backtrace if possible to the journal and store the core dump itself in an external file in `/var/lib/systemd/coredump`.

The behavior of a specific program upon reception of a signal is governed by a few factors which are described in detail in core 5. In particular, the core dump will only be processed when the related resource limits are sufficient.

It is also possible to invoke `systemd-coredump` with `--backtrace` option. In this case, `systemd-coredump` expects a journal entry in the journal Journal Export Format on standard input. The entry should contain a `MESSAGE=` field and any additional metadata fields the caller deems reasonable. `systemd-coredump` will append additional metadata fields in the same way it does for core dumps received from the kernel. In this mode, no core dump is stored in the journal.

## Configuration

For programs started by `systemd` process resource limits can be set by directive `LimitCore=`, see systemd.exec 5.

In order to be used by the kernel to handle core dumps, `systemd-coredump` must be configured in sysctl 8 parameter `kernel.core_pattern`. The syntax of this parameter is explained in core 5. Systemd installs the file `/usr/lib/sysctl.d/50-coredump.conf` which configures `kernel.core_pattern` accordingly. This file may be masked or overridden to use a different setting following normal sysctl.d 5 rules. If the sysctl configuration is modified, it must be updated in the kernel before it takes effect, see sysctl 8 and systemd-sysctl 8.

In order to by used in the `--backtrace` mode, an appropriate backtrace handler must be installed on the sender side. For example, in case of python 1, this means a `sys.excepthook` must installed, see systemd-coredump-python.

The behavior of `systemd-coredump` itself is configured through the configuration file `/etc/systemd/coredump.conf` and corresponding snippets `/etc/systemd/coredump.conf.d/*.conf`, see coredump.conf 5. A new instance of `systemd-coredump` is invoked upon receiving every core dump. Therefore, changes in these files will take effect the next time a core dump is received.

Resources used by core dump files are restricted in two ways. Parameters like maximum size of acquired core dumps and files can be set in files `/etc/systemd/coredump.conf` and snippets mentioned above. In addition the storage time of core dump files is restricted by `systemd-tmpfiles`, corresponding settings are by default in `/usr/lib/tmpfiles.d/systemd.conf`.

## Usage

Data stored in the journal can be viewed with journalctl 1 as usual. coredumpctl 1 can be used to retrieve saved core dumps independent of their location, to display information and to process them e.g. by passing to the GNU debugger (gdb).

## See Also

coredump.conf 5, coredumpctl 1, systemd-journald.service 8, systemd-tmpfiles 8, core 5, sysctl.d 5, systemd-sysctl.service 8.