3.2 KiB
EPICS
Where is EPICS Base (https://gitea.psi.ch/epics) installed?
echo $EPICS
Host architecture that EPICS Base runs on:
echo $EPICS_HOST_ARCH
Which channel access lib is being used in python?
[sls-vserv-bd-hla01-dev ~]$ which python
/bin/python
[sls-vserv-bd-hla01-dev playground]$ python3 -c "import ctypes; import epics.ca; print(epics.ca.find_libca())"
/usr/local/epics/base-7.0.9/lib/RHEL9-x86_64/libca.so
[sls-vserv-bd-hla01-dev ~]$ source /opt/gfa/python-3.10/latest/bin/activate
(base) [sls-vserv-bd-hla01-dev ~]$ which python
/opt/gfa/python-3.10/20220602/bin/python
(base) [sls-vserv-bd-hla01-dev ~]$ python3 -c "import ctypes; import epics.ca; print(epics.ca.find_libca())"
/opt/gfa/python-3.10/20220602/epics/lib/linux-x86_64/libca.so
How does the conda env configure which EPICS to use?
(base) [sls-vserv-bd-hla01-dev ~]$ cat /opt/gfa/python-3.10/20220602/etc/conda/activate.d/epics-base_activate.sh
export EPICS_BASE="/opt/gfa/python-3.10/20220602/epics"
export EPICS_HOST_ARCH="linux-x86_64"
export EPICS_BASE_HOST_BIN="/opt/gfa/python-3.10/20220602/epics/bin/linux-x86_64"
export EPICS_BASE_VERSION="7.0.5.0"
export PATH=$EPICS_BASE_HOST_BIN:$PATH
How does the conda env configure which EPICS python uses?
(base) [sls-vserv-bd-hla01-dev ~]$ cat /opt/gfa/python-3.10/20220602/etc/conda/activate.d/pyepics_activate.sh
export PYEPICS_LIBCA="${EPICS_BASE}/lib/${EPICS_HOST_ARCH}/libca.so"
Example reading from a PV:
[sls-vserv-bd-hla01-dev ~]$ /bin/python
Python 3.9.25 (main, Apr 17 2026, 00:00:00)
[GCC 11.5.0 20240719 (Red Hat 11.5.0-14)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from epics import PV
>>> pv = PV("AGEBD-PLAYGROUND-DEV:AO")
>>> pv.get()
5.0
>>>
System python installed packages
/bin/python -m pip list -v
Systemd Services
When ssh-ing into a machine, /etc/profile.d/* automatically gets sourced. And thus we have:
[sls-vserv-bd-hla01-dev ~]$ env | grep EPICS
EPICS_CA_ADDR_LIST=sls-cagw.psi.ch:5062
When running a systemd service, this does not happen.
Note -- it seems that the following does not work as expected:
That's why we need to source `/etc/profile.d/cas_12_epics.sh` in our startup script
to make sure that `EPICS` is configured properly.
After sourcing the script, we still have: EPICS_CA_ADDR_LIST= (i.e. the script does not set EPICS_CA_ADDR_LIST=sls-cagw.psi.ch:5062) in systemd service.
Whereas in the shell unset EPICS_CA_ADDR_LIST and then . /etc/profile/cas_12_epics.sh properly sets EPICS_CA_ADDR_LIST=sls-cagw.psi.ch:5062.
Check which env variables a systemd service is running with:
[sls-vserv-bd-hla01-dev ~]$ systemctl --user restart AGEBD-SERVICE-SCRUBBING.service && sleep 1 && PID=$(systemctl --user show -p MainPID --value AGEBD-SERVICE-SCRUBBING.service)
[sls-vserv-bd-hla01-dev ~]$ tr '\0' '\n' < /proc/$PID/environ | grep EPICS
EPICS_CAS_IGNORE_ADDR_LIST=
EPICS_CA_ADDR_LIST= 129.129.146.255
EPICS_HOST_ARCH=linux-x86_64
EPICS_BASE_HOST_BIN=/opt/gfa/python-3.10/20220602/epics/bin/linux-x86_64
PYEPICS_LIBCA=/opt/gfa/python-3.10/20220602/epics/lib/linux-x86_64/libca.so
EPICS_BASE_VERSION=7.0.5.0
EPICS_BASE=/opt/gfa/python-3.10/20220602/epics