Good day.
The steps listed below are for the configuration of hard and soft file
limits.
The listed configuration for systemd only configures the hard limit. It
is apparent that some additional process is required to configure the
soft limit in this instance. This has not been observed before because
the prlimit command output in both Debian 12 and Debian 13 shows that
the soft limit is set by default to a value of 1024. Therefore issues
are only being encountered when there are more than 1000 layers in a
Qgis project.
I use qgis to process large numbers of raster layers that are loaded
from files and at time there are more than 1000 of these layers in a
particular series therefore this situation often arises for me.
I will be investigating how to configure the soft limit on these
operating systems.
On 17/09/2024 01:31, Patrick Dunford wrote:
Good day
For many years it has been known that applications such as Qgis
running under the Linux operating system have been subject to
configuration of maximum number of file descriptors for open files.
Generally the default is set to something like 1024 and will affect
Qgis projects with more than 1024 layers.
There are currently two limits in Linux that may affect users of Qgis
with a large number of layers in their project. These can be checked
using the ulimit -n command which will display the maximum number of
open files permitted in the current configuration.
1. PAM session limits are configured in the file
/etc/security/limits.conf
2. On some distros, the limits also have to be separately configured
for systemd.
Ubuntu up to and including 22.04 requires only step 1 to be completed.
Debian 12 on the other hand requires step 2 to be completed. It is not
clear if this is a requirement on any other releases of Debian.
However experience suggests this step has not been a requirement on
most earlier Debian releases.
The specifics as far as I can determine for step 2 suggest that a
.conf file is placed in the following path:
/etc/systemd/user.conf.d
This file can be any name chosen by a user (e.g. limits.conf). The
file was copied from the user.conf file placed in /etc/systemd and it
is also the case that editing this user.conf file in its default path
would have the same effect, however the subdirectory usage is
recommended.
This file must at a minimum contain the following:
[Manager]
DefaultLimitNOFILE=xxxxxx
This is a per-user limit and it does not apply to the root user. There
is a different procedure for the root user, which I do not have
documentation for. The result of ulimit -n run under a root shell will
display a different result from running it as a non-root user.
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