ulimit and lsof

PID of WLS is 29518
to count how many file descriptors are held by a process:
ls /proc/29518/fd | wc -l
666

funnily this doesn’t match the count reported by lsof ( one day I will discover why):

lsof -p 29518 | wc -l
1288

to know the limit for the specific process:

cat /proc/29518/limits
Limit Soft Limit Hard Limit Units
Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes
Max data size unlimited unlimited bytes
Max stack size 10485760 unlimited bytes
Max core file size 0 0 bytes
Max resident set unlimited unlimited bytes
Max processes 32000 32000 processes
Max open files 1024 1024 files
Max locked memory 65536 65536 bytes
Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks
Max pending signals 515304 515304 signals
Max msgqueue size 819200 819200 bytes
Max nice priority 0 0
Max realtime priority 0 0
Max realtime timeout unlimited unlimited us

which is different for the limit set by default for a user:

ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 515304
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 8192
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 10240
cpu time (seconds, -t) unlimited
max user processes (-u) 1024
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited

To set the limit for a process open by the current shell :

ulimit -n MAX_FD_PER_PROCESS


In Linux, this is a PER-PROCESS limit! You cannot directly limit the number of Files opened by a User! You can only set a max-processes-per-user with ulimit -u MAX .
to check the actual limits for a process:
cat /proc//limits
cat /etc/security/limits.conf to check the hard limits for all users. If you try to set a ulimit larger than that. you get a ulimit: open files: cannot modify limit: Operation not permitted