What file under the proc directory contains information regarding what modules are currently loaded into the Linux kernal?

05 Jan 2020

• linux

The proc filesystem is a pseudo-filesystem which provides an interface to kernel data structures. – linux man pages

/proc directory is not a real filesystem, it is a Virtual File System. It contains information about processes and other system information. It is mapped to /proc and mounted at boot time.

Running a ls in /proc lists a bunch of numbered directories and a bunch of files. The numbered directories are process PIDs and contains information related to the process.

We can get information about what file contains man 5 /proc/.

Quick description of some files

• /proc/cmdline – Kernel command line information.
• /proc/console – Information about current consoles including tty.
• /proc/devices – Device drivers currently configured for the running kernel.
• /proc/dma – Info about current DMA channels.
• /proc/fb – Framebuffer devices.
• /proc/filesystems – Current filesystems supported by the kernel.
• /proc/iomem – Current system memory map for devices.
• /proc/ioports – Registered port regions for input output communication with device.
• /proc/loadavg – System load average.
• /proc/locks – Files currently locked by kernel.
• /proc/meminfo – Info about system memory (see above example).
• /proc/misc – Miscellaneous drivers registered for miscellaneous major device.
• /proc/modules – Currently loaded kernel modules.
• /proc/mounts – List of all mounts in use by system.
• /proc/partitions – Detailed info about partitions available to the system.
• /proc/pci – Information about every PCI device.
• /proc/stat – Record or various statistics kept from last reboot.
• /proc/swap – Information about swap space.
• /proc/uptime – Uptime information (in seconds).
• /proc/version – Kernel version, gcc version, and Linux distribution installed.

/proc/

$ ls -l /proc/1 dr-xr-xr-x 2 root root 0 Jan 3 11:46 attr -rw-r--r-- 1 root root 0 Jan 5 09:29 autogroup -r-------- 1 root root 0 Jan 5 09:29 auxv -r--r--r-- 1 root root 0 Jan 3 11:46 cgroup --w------- 1 root root 0 Jan 5 09:29 clear_refs -r--r--r-- 1 root root 0 Jan 3 22:57 cmdline -rw-r--r-- 1 root root 0 Jan 3 11:46 comm -rw-r--r-- 1 root root 0 Jan 5 09:29 coredump_filter -r--r--r-- 1 root root 0 Jan 5 09:29 cpuset lrwxrwxrwx 1 root root 0 Jan 5 09:29 cwd -> / -r-------- 1 root root 0 Jan 3 11:46 environ lrwxrwxrwx 1 root root 0 Jan 3 22:57 exe -> /lib/systemd/systemd dr-x------ 2 root root 0 Jan 3 11:46 fd dr-x------ 2 root root 0 Jan 3 11:46 fdinfo -rw-r--r-- 1 root root 0 Jan 3 11:46 gid_map -r-------- 1 root root 0 Jan 5 09:29 io -r--r--r-- 1 root root 0 Jan 3 11:50 limits -rw-r--r-- 1 root root 0 Jan 3 11:46 loginuid dr-x------ 2 root root 0 Jan 5 09:29 map_files -r--r--r-- 1 root root 0 Jan 5 09:29 maps -rw------- 1 root root 0 Jan 5 09:29 mem -r--r--r-- 1 root root 0 Jan 3 11:46 mountinfo -r--r--r-- 1 root root 0 Jan 5 09:29 mounts -r-------- 1 root root 0 Jan 5 09:29 mountstats dr-xr-xr-x 5 root root 0 Jan 3 11:46 net dr-x--x--x 2 root root 0 Jan 5 09:29 ns -r--r--r-- 1 root root 0 Jan 5 09:29 numa_maps -rw-r--r-- 1 root root 0 Jan 5 09:29 oom_adj -r--r--r-- 1 root root 0 Jan 5 09:29 oom_score -rw-r--r-- 1 root root 0 Jan 3 11:46 oom_score_adj -r-------- 1 root root 0 Jan 5 09:29 pagemap -r-------- 1 root root 0 Jan 5 09:29 patch_state -r-------- 1 root root 0 Jan 5 09:29 personality -rw-r--r-- 1 root root 0 Jan 5 09:29 projid_map lrwxrwxrwx 1 root root 0 Jan 3 11:46 root -> / -rw-r--r-- 1 root root 0 Jan 3 11:46 sched -r--r--r-- 1 root root 0 Jan 5 09:29 schedstat -r--r--r-- 1 root root 0 Jan 3 11:46 sessionid -rw-r--r-- 1 root root 0 Jan 3 11:46 setgroups -r--r--r-- 1 root root 0 Jan 5 09:29 smaps -r--r--r-- 1 root root 0 Jan 5 09:29 smaps_rollup -r-------- 1 root root 0 Jan 5 09:29 stack -r--r--r-- 1 root root 0 Jan 3 11:46 stat -r--r--r-- 1 root root 0 Jan 3 12:07 statm -r--r--r-- 1 root root 0 Jan 3 11:46 status -r-------- 1 root root 0 Jan 5 09:29 syscall dr-xr-xr-x 3 root root 0 Jan 3 11:46 task -r--r--r-- 1 root root 0 Jan 5 09:29 timers -rw-rw-rw- 1 root root 0 Jan 5 09:29 timerslack_ns -rw-r--r-- 1 root root 0 Jan 3 11:46 uid_map -r--r--r-- 1 root root 0 Jan 5 09:29 wchan

Print the contents of any file to see what it contains,

$ cat /proc/1/status Name: systemd State: S (sleeping) Tgid: 1 Ngid: 0 Pid: 1 PPid: 0 TracerPid: 0 Uid: 0 0 0 0 Gid: 0 0 0 0 FDSize: 256 ...

We can gather that the process with PID 1 has name systemd and its current state is sleeping. The user id (Uid) and group id (Gid) are 0, which means they belong to root user.

The most common files inside a pid directory are

• cmdline – complete command line for the process, unless the process is a zombie
• environ – environmental variables
• fd – file descriptors
• limits – displays the soft limit, hard limit, and units of measurement for each of the process’s resource limits
• mounts – related information
• cwd – symbolic link to the current working directory of the process
• exe – link to the executable of the process
• root – link to the work directory of the process
• cgroup - describes control groups to which the process/task belongs

Reference

• proc(5) - Linux man page

What file in the proc folder contains details about the CPU?

What is the proc directory in Linux?

What can be found in the proc directory?

Which of the directory contains process and kernel information files?