Kernel Information

• Many of the entries in /proc provide access to information about the running kernel's configuration and state. Some of these entries are at the top level of /proc; others are under /proc/sys/kernel.
  • kcore Information; /proc/kcore file is the physical memory of the system in core file format. It is used with GDB to examine kernel data structures. This file is not in a text format.
  • kmsg Information; /proc/kmsg file; only one process, which must have root privileges, can read this file at any given time. This is used to retrieve kernel messages generated using printk().
  • ksyms Information; /proc/ksyms file lists the kernel symbols that have been registered; these symbols give the address of a variable or function.
    • Each line gives the address of a symbol, the name of the symbol, and the module that registered the symbol.
    • The ksyms, insmod, and kmod programs probably use this file. It also lists the number of running tasks, the total number of tasks, and the last pid assigned.
  • Modules Information; /proc/modules file gives information on loadable kernel modules. This information is used by the lsmod program to display the information on the name, size, usecount, and referring modules.
  • Version Information; the file /proc/version contains a long string describing the kernel's release number and build version. It also includes information about how the kernel was built: the user who compiled it, the machine on which it was compiled, the date it was compiled, and the compiler release that was used.

    $ cat /proc/version
    $ cat /proc/sys/kernel/ostype
    $ cat /proc/sys/kernel/osrelease
    $ cat /proc/sys/kernel/version
    

  • Hostname and Domain Name; the /proc/sys/kernel/hostname and /proc/sys/kernel/domainname entries contain the computer's hostname and domain name, respectively.
  • Memory Usage; the /proc/meminfo entry contains information about the system's memory usage.

    $ cat /proc/meminfo
    

    • The Shared column displays total shared memory currently allocated on the system.
    • The Buffers column displays the memory allocated by Linux for block device buffers. These buffers are used by device drivers to hold blocks of data being read from and written to disk.
    • The Cached column displays the memory allocated by Linux to the page cache. This memory is used to cache accesses to mapped files.
    • You can use the free command to display the same memory information.