Linux – /proc//net/dev

When dealing with applications that are using up network bandwidth the best tool I've come across for tying back utilization to specific apps has got to be nethogs.

You can use ip link show or netstat -i to find out your network interface names.

$ netstat -i
Kernel Interface table
Iface      MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
em1       1500        0      0      0 0             0      0      0      0 BMU
lo       65536    81375      0      0 0         81375      0      0      0 LRU
virbr0    1500        0      0      0 0             0      0      0      0 BMU
wlp3s0    1500  2264942      0      0 0       2376236      0      0      0 BMRU

My wireless on my Fedora 19 laptop is wlp3s0, so we tell nethogs to watch that:

$ sudo nethogs wlp3s0

As you let nethogs run it will start to show you the applications that are consuming your network bandwidth.

/dev/console exists primarily to expose the kernel’s console to userspace. The Linux kernel’s documentation on devices now says

The console device, /dev/console, is the device to which system messages should be sent, and on which logins should be permitted in single-user mode. Starting with Linux 2.1.71, /dev/console is managed by the kernel; for previous versions it should be a symbolic link to either /dev/tty0, a specific virtual console such as /dev/tty1, or to a serial port primary (tty*, not cu*) device, depending on the configuration of the system.

/dev/console, the device node with major 5 and minor 1, provides access to whatever the kernel considers to be its primary means of interacting with the system administrator; this can be a physical console connected to the system (with the virtual console abstraction on top, so it can use tty0 or any ttyN where N is between 1 and 63), or a serial console, or a hypervisor console, or even a Braille device. Note that the kernel itself doesn’t use /dev/console: devices nodes are for userspace, not for the kernel; it does, however, check that /dev/console exists and is usable, and sets init up with its standard input, output and error pointing to /dev/console.

As described here, /dev/console is a character device with a fixed major and minor because it’s a separate device (as in, a means of accessing the kernel; not a physical device), not equivalent to /dev/tty0 or any other device. This is somewhat similar to the situation with /dev/tty which is its own device (5:0) because it provides slightly different features than the other virtual console or terminal devices.

The “list of consoles” is indeed the list of consoles defined by the console= boot parameters (or the default console, if there are none). You can see the consoles defined in this way by looking at /proc/consoles. /dev/console does indeed provide access to the last of these:

You can specify multiple console= options on the kernel command line. Output will appear on all of them. The last device will be used when you open /dev/console.