Server settings for a LXD production setup

To allow your LXD server to run a large number of instances, configure the following settings to avoid hitting server limits.

The Value column contains the suggested value for each parameter.

/etc/security/limits.conf

Note

For users of the snap, those limits are automatically raised.

Domain	Type	Item	Value	Default	Description
*	soft	nofile	1048576	unset	Maximum number of open files
*	hard	nofile	1048576	unset	Maximum number of open files
root	soft	nofile	1048576	unset	Maximum number of open files
root	hard	nofile	1048576	unset	Maximum number of open files
*	soft	memlock	unlimited	unset	Maximum locked-in-memory address space (KB)
*	hard	memlock	unlimited	unset	Maximum locked-in-memory address space (KB)
root	soft	memlock	unlimited	unset	Maximum locked-in-memory address space (KB), only need with bpf syscall supervision
root	hard	memlock	unlimited	unset	Maximum locked-in-memory address space (KB), only need with bpf syscall supervision

/etc/sysctl.conf

Note

Reboot the server after changing any of these parameters.

Parameter	Value	Default	Description
fs.aio-max-nr	524288	65536	Maximum number of concurrent asynchronous I/O operations (you might need to increase this limit further if you have a lot of workloads that use the AIO subsystem, for example, MySQL)
fs.inotify.max_queued_events	1048576	16384	Upper limit on the number of events that can be queued to the corresponding inotify instance (see inotify)
fs.inotify.max_user_instances	1048576	128	Upper limit on the number of inotify instances that can be created per real user ID (see inotify)
fs.inotify.max_user_watches	1048576	8192	Upper limit on the number of watches that can be created per real user ID (see inotify)
kernel.dmesg_restrict	1	0	Whether to deny container access to the messages in the kernel ring buffer (note that this will also deny access to non-root users on the host system)
kernel.keys.maxbytes	2000000	20000	Maximum size of the key ring that non-root users can use
kernel.keys.maxkeys	2000	200	Maximum number of keys that a non-root user can use (the value should be higher than the number of instances)
net.core.bpf_jit_limit	1000000000	varies	Limit on the size of eBPF JIT allocations (on kernels < 5.15 that are compiled with CONFIG_BPF_JIT_ALWAYS_ON=y, this value might limit the amount of instances that can be created)
net.ipv4.neigh.default.gc_thresh3	8192	1024	Maximum number of entries in the IPv4 ARP table (increase this value if you plan to create over 1024 instances - otherwise, you will get the error neighbour: ndisc_cache: neighbor table overflow! when the ARP table gets full and the instances cannot get a network configuration; see ip-sysctl)
net.ipv6.neigh.default.gc_thresh3	8192	1024	Maximum number of entries in IPv6 ARP table (increase this value if you plan to create over 1024 instances - otherwise, you will get the error neighbour: ndisc_cache: neighbor table overflow! when the ARP table gets full and the instances cannot get a network configuration; see ip-sysctl)
vm.max_map_count	262144	65530	Maximum number of memory map areas a process may have (memory map areas are used as a side-effect of calling malloc, directly by mmap and mprotect, and also when loading shared libraries)