Linux上的用户和Linux系统的打开文件数量是多少？

我正在开发的应用程序日志中收到“太多打开文件”消息.有人建议我：

>查找当前正在使用的打开文件数,系统范围和每个用户
>查找系统和用户打开文件的限制.

我运行ulimit -n并返回1024.我还查看了/etc/limits.conf并且该文件中没有任何特殊内容. /etc/sysctl.conf也未修改.我将列出以下文件的内容.我也跑了lsof | wc -l,返回5000行(如果我正确使用它).

所以,我的主要问题是：

>如何找到每个用户允许的打开文件数？软限制是在/etc/limits.conf中找到/定义的nofile设置吗？什么是默认值,因为我没有触及/etc/limits.conf？
>如何在系统范围内找到允许的打开文件数？它是limits.conf中的硬限制吗？如果不修改limits.conf,默认值是多少？
> ulimit为打开文件返回的数字是多少？它说1024但是当我运行lsof并计算线数时,它超过5000,所以有些东西不是我的点击.是否应该运行其他cmds或查看文件以获得这些限制？在此先感谢您的帮助.

limits.conf的内容

# /etc/security/limits.conf
#
#Each line describes a limit for a user in the form:
#
#<domain>        <type>  <item>  <value>
#
#Where:
#<domain> can be:
#        - an user name
#        - a group name,with @group syntax
#        - the wildcard *,for default entry
#        - the wildcard %,can be also used with %group syntax,#                 for maxlogin limit
#
#<type> can have the two values:
#        - "soft" for enforcing the soft limits
#        - "hard" for enforcing hard limits
#
#<item> can be one of the following:
#        - core - limits the core file size (KB)
#        - data - max data size (KB)
#        - fsize - maximum filesize (KB)
#        - memlock - max locked-in-memory address space (KB)
#        - nofile - max number of open files
#        - rss - max resident set size (KB)
#        - stack - max stack size (KB)
#        - cpu - max CPU time (MIN)
#        - nproc - max number of processes
#        - as - address space limit (KB)
#        - maxlogins - max number of logins for this user
#        - maxsyslogins - max number of logins on the system
#        - priority - the priority to run user process with
#        - locks - max number of file locks the user can hold
#        - sigpending - max number of pending signals
#        - msgqueue - max memory used by POSIX message queues (bytes)
#        - nice - max nice priority allowed to raise to values: [-20,19]
#        - rtprio - max realtime priority
#
#<domain>      <type>  <item>         <value>
#

#*               soft    core            0
#*               hard    rss             10000
#@student        hard    nproc           20
#@faculty        soft    nproc           20
#@faculty        hard    nproc           50
#ftp             hard    nproc           0
#@student        -       maxlogins       4

# End of file

sysctl.conf的内容

# Controls IP packet forwarding
net.ipv4.ip_forward = 0

# Controls source route verification
net.ipv4.conf.default.rp_filter = 1

# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0

# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0

# Controls whether core dumps will append the PID to the core filename
# Useful for debugging multi-threaded applications
kernel.core_uses_pid = 1

# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1

# Controls the maximum size of a message,in bytes
kernel.msgmnb = 65536

# Controls the default maxmimum size of a mesage queue
kernel.msgmax = 65536

# Controls the maximum shared segment size,in bytes
kernel.shmmax = 68719476736

# Controls the maximum number of shared memory segments,in pages
kernel.shmall = 4294967296

# the interval between the last data packet sent and the first keepalive probe
net.ipv4.tcp_keepalive_time = 600

# the interval between subsequential keepalive probes
net.ipv4.tcp_keepalive_intvl = 60

# the interval between the last data packet sent and the first keepalive probe
net.ipv4.tcp_keepalive_time = 600

# the interval between subsequential keepalive probes
net.ipv4.tcp_keepalive_intvl = 60

# the number of unacknowledged probes to send before considering the connection dead and notifying the application layer
net.ipv4.tcp_keepalive_probes = 10

# the number of unacknowledged probes to send before considering the connection dead and notifying the application layer
net.ipv4.tcp_keepalive_probes = 10

# try as hard as possible not to swap,as safely as possible
vm.swappiness = 1
fs.aio-max-nr = 1048576
#fs.file-max = 4096