Linux查看及修改系统的资源限制命令ulimit

在Linux，查看系统对资源使用的显示可以使用命令ulimit，其中参数-a会列出所有的资源使用限制。

[demo@server ~]$ 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) 2055823
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 65535
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 4096
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

修改系统的资源对用户的使用限制

资源对用户的使用限制在/etc/security/limits.conf文件里配置。如下：

demo@server:~$ cat /etc/security/limits.conf   
# /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 # 软限制，必须必硬限制的值要小  
#        - "hard" for enforcing hard limits     # 硬限制  
#  
#<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    # 最大打开的文件数(以文件描叙符，file descripter计数)  
#        - 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  
#        - 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  
#        - rtprio - max realtime priority  
#  
#<domain>      <type>  <item>         <value>  
#  
root            soft    nofile          200000  
root            hard    nofile          200000  
admin           hard    nofile          65536  
admin           soft    nofile          65536  
# End of file  

对资源使用限制的配置是针对用户或者用户组，每行格式如下：

用户名/用户组 类型(硬限制hard、软限制soft) 选项 值

其中类型的值可以为hard，soft或者“-”，其中“-”相当于同时配置了hard和soft两行。

注意：退出重新登录后，配置生效