If you occasionally see the following error when running backups or file copies on Linux:
Limit for the maximum number of semaphores reached. You can check and set the limits in /proc/sys/kernel/sem.\n
You may need to increase the maximum number of semaphores on your Linux server.
If you read the manpage for semget, in the Notes section you'll notice:
System wide maximum number of semaphore sets: policy dependent (on Linux, this limit can be read and modified via the fourth field of /proc/sys/kernel/sem).
You can check the current semaphore limit on your server by running:
cat /proc/sys/kernel/sem 250 32000 32 128
Then to increase the limit to 200 for example echo it back after increasing the last number:
printf '250\t32000\t32\t200' >/proc/sys/kernel/sem