Sunrpc settings are not persistent after reboot.

This document (7022831) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server 12

Situation

SUNRPC tunables in /etc/sysctl.conf such as "sunrpc.tcp_max_slot_table_entries" may not take effect during boot. They still can be set after boot by executing "sysctl -p" which will read the settings again from /etc/sysctl.conf.

After such a boot, the following type of error can be found in /var/log/messages:

error systemd-sysctl[941]: Couldn't write '128' to 'sunrpc/tcp_max_slot_table_entries', ignoring: No such file or directory.

Resolution

The sunrpc module does not always load before systemd-sysctl.service starts, and in those cases, sunrpc settings within sysctl.conf (or other sysctl locations) cannot come into effect.

There are several possible ways to address this. The two easiest are:

1. For distributions of SLES which still receive maintenance updates, new nfs-utils packages will cause the sunrpc module to activate sysctl settings when it loads. So even if those settings could not come into effect during boot, they will come into effect later.

Packages that need updating are nfs-client and (if present) nfs-kernel-server, which together are also known as "nfs-utils" because they both come from a source code package with that name.

Distribution	Minimum nfs-client version
SLES 15 SP4	2.1.1-150100.10.32.1
SLES 15 SP3 (LTSS)	2.1.1-150100.10.37.1
SLES 15 SP2 (LTSS)	2.1.1-150100.10.37.1
SLES 15 SP1 (LTSS)	2.1.1-150100.10.37.1
SLES 12 SP5	1.3.0-34.42.1

2. Where the update (#1) is not available, the sunrpc module can be forced to load earlier in the boot sequence. Give the following command, which will create the following file with "sunrpc" as contents:

echo sunrpc > /etc/modules-load.d/sunrpc.conf

Upon the next boot, sunrpc will load earlier and systemd-sysctl should successfully set the sunrpc values.

Cause

In some configurations, the sunrpc kernel module is not loaded before systemd-sysctl service is started.

Additional Information

Potential sunrpc settings that can be set in /etc/sysctl.conf
sunrpc.max_resvport = 1023
sunrpc.min_resvport = 665
sunrpc.nfs_debug = 0x0000
sunrpc.nfsd_debug = 0x0000
sunrpc.nlm_debug = 0x0000
sunrpc.rpc_debug = 0x0000
sunrpc.tcp_fin_timeout = 15
sunrpc.tcp_max_slot_table_entries = 65536
sunrpc.tcp_slot_table_entries = 2
sunrpc.transports = tcp 1048576
sunrpc.transports = udp 32768
sunrpc.transports = tcp-bc 1048576
sunrpc.udp_slot_table_entries = 16

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