Shell how to show all interfaces in linux
This can be done faster with the specialized command which deals with namespaces, but appears to handle only processes (not mount points nor open fd as seen later): (which would have to be reformatted for later as ) mount point Those are mostly used by the command which creates permanent network namespaces by mounting them, thus avoiding them disappearing when there is no process nor fd resource keeping them up, then also allowing for example to run a router, firewall or bridge in a network namespace without any linked process. The init (initial) network namespace, except for inheriting physical interfaces of destroyed network namespaces has no special ability over other network namespaces: it can’t see directly their interfaces.
How do I find all interfaces that have been configured in Linux, including those of containers?
An interface, at a given time, belongs to one network namespace and only one. The init (initial) network namespace, except for inheriting physical interfaces of destroyed network namespaces has no special ability over other network namespaces: it can’t see directly their interfaces. As long as you are still in init’s pid and mount namespaces, you can still find the network namespaces by using different informations available from /proc and finally display their interfaces by entering those network namespaces.
I’ll provide examples in shell.
- enumerate the network namespaces For this you have to know how those namespaces are existing: as long as a resource keep them up. A resource here can be a process (actually a process’ thread), a mount point or an open file descriptor (fd). Those resources are all referenced in /proc/ and point to an abstract pseudo-file in the nsfs pseudo-filesystem enumerating all namespaces. This file’s only meaningful information is its inode, representing the network namespace, but the inode can’t be manipulated alone, it has to be the file. That’s why later we can’t just keep only the inode value (given by stat -c %i /proc/some/file ): we’ll keep the inode to be able to remove duplicates and a filename to still have an usable reference for nsenter later.
- process (actually thread) The most common case: for usual containers. Each thread’s network namespace can be known via the reference /proc/pid/ns/net : just stat them and enumerate all unique namespaces. The 2>/dev/null is to hide when stat can’t find ephemeral processes anymore.
find /proc/ -mindepth 1 -maxdepth 1 -name '3*' | while read -r procpid; do stat -L -c '%20i %n' $procpid/ns/net done 2>/dev/null This can be done faster with the specialized lsns command which deals with namespaces, but appears to handle only processes (not mount points nor open fd as seen later):
awk '$3 == "nsfs" < print $2 >' /proc/mounts | while read -r mount; do stat -c '%20i %n' "$mount" done find /proc/ -mindepth 1 -maxdepth 1 -name '2*' | while read -r procpid; do find $procpid/fd -mindepth 1 | while read -r procfd; do if [ "$(stat -f -c %T $procfd)" = nsfs ]; then stat -L -c '%20i %n' $procfd fi done done 2>/dev/null Now remove all duplicate network namespace references from previous results. Eg by using this filter on the combined output of the 3 previous results (especially from the open file descriptor part):
while read -r inode reference; do if nsenter --net="$reference" ip -br address show 2>/dev/null; then printf 'end of network %d\n\n' $inode fi done The init network’s inode can be printed with pid 1 as reference:
echo -n 'INIT NETWORK: ' ; stat -L -c %i /proc/1/ns/net Example (real but redacted) output with a running LXC container,an empty «mounted» network namepace created with ip netns add . having an unconnected bridge interface, a network namespace with an other dummy0 interface, kept alive by a process not in this network namespace but keeping an open fd on it, created with:
unshare --net sh -c 'ip link add dummy0 type dummy; ip address add dev dummy0 10.11.12.13/24; sleep 3' & sleep 1; sleep 999 < /proc/$!/ns/net & and a running Firefox which isolates each of its "Web Content" threads in an unconnected network namespace (all those down lo interfaces):
lo UNKNOWN 127.0.0.1/8 ::1/128 eth0 UP 192.0.2.2/24 2001:db8:0:1:bc5c:95c7:4ea6:f94f/64 fe80::b4f0:7aff:fe76:76a8/64 wlan0 DOWN dummy0 UNKNOWN 198.51.100.2/24 fe80::108a:83ff:fe05:e0da/64 lxcbr0 UP 10.0.3.1/24 2001:db8:0:4::1/64 fe80::216:3eff:fe00:0/64 virbr0 DOWN 192.168.122.1/24 virbr0-nic DOWN vethSOEPSH@if9 UP fe80::fc8e:ff:fe85:476f/64 end of network 4026531992 lo DOWN end of network 4026532418 lo DOWN end of network 4026532518 lo DOWN end of network 4026532618 lo DOWN end of network 4026532718 lo UNKNOWN 127.0.0.1/8 ::1/128 eth0@if10 UP 10.0.3.66/24 fe80::216:3eff:fe6a:c1e9/64 end of network 4026532822 lo DOWN bridge0 UNKNOWN fe80::b884:44ff:feaf:dca3/64 end of network 4026532923 lo DOWN dummy0 DOWN 10.11.12.13/24 end of network 4026533021 INIT NETWORK: 4026531992
ip netns list will only list the networks namespaces which were configured via the ip-netns(8) utility.
The lsns(1) program from the util-linux package is also highly deficient : it will list only those namespaces which are accessible via the /proc//ns/* files, omitting all the per-thread namespaces and those kept alive by a bind mount or an open file descriptor.
The following demo script tries to do better: it will look for bind mounts through the /proc//task//mountinfo files, and for open fds through /proc//task//fd files.
For each namespace, it will print a path through which it is accessible:
# perl ./lsnsx.pl . mnt 3 4026531840 /proc/1/ns/mnt 4026531860 /proc/30/ns/mnt 4026532374 /proc/3119/ns/mnt net 6 4026531992 /proc/1/ns/net 4026532376 /proc/25781/fd/9 4026532465 /proc/28373/fd/7 . You can then use that path with nsenter(1) , eg.
nsenter --net=/proc/28373/fd/7 ip link The script could be easily changed to do that itself, or show other info, like the whole list of processes which use a namespace.
If the path is not accessible, it will follow it by the parent/mount ids and the /proc//mountinfo file where it was found. Escaped newlines, tabs and spaces will be left as they are:
net 9 . 4026532732 /v/net\040ns /proc/3119/mountinfo 60 41 Since it has to read all those /proc/*/task/* files, this may get slow on any machine where heavily threaded programs are used; unfortunately I wasn't able to find any quick way to check if two threads/tasks share the same namespace(s): kcmp(2) will only tell if they're sharing the same address space, file descriptor table, etc; not anything namespace-related.
#! /usr/bin/perl use strict; my %t2n = ( # the CLONE_NEW* from sched.h 0x02000000 => "cgroup", 0x04000000 => "uts", 0x08000000 => "ipc", 0x10000000 => "user", 0x20000000 => "pid", 0x40000000 => "net", 0x00020000 => "mnt" # CLONE_NEWNS ); my (%ns); my $nsfs_dev = (stat "/proc/self/ns/mnt")[0]; my $type = shift || qr/\w+/; sub unescape < $_[0] =~ s/\\(5)/chr oct $1/ger > # NS_GET_NSTYPE = 0xb7 for()< s; if(my ($procpid) = m<(.*)/mountinfo$>)< open my $h, $_ or next; LOOP: while()< next unless (my @s = split)[2] eq "0:$nsfs_dev"; if(my($t, $i) = $s[3] =~ /^($type):\[(\d+)\]$/)< next if exists $ns; for ("", "$procpid/root")< my ($d, $i1) = (stat $_.unescape $s[4])[0, 1]; $ns = $_.$s[4], next LOOP if $d == $nsfs_dev && $i == $i1; > $ns = "@s[4, 0, 1] $procpid/mountinfo" > > >elsif(m)< $ns //= $_ if readlink =~ /^($type):\[(\d+)\]$/; >else< next unless my ($dev, $ino) = stat $_; next unless $dev == $nsfs_dev; next unless my $t = nstype $_; next if ($t = $t2n) and $t !~ $type; $ns //= $_; > > for my $type (sort keys %ns)< my $h = $ns; my @i = sort $b> keys %$h; printf "%-8s %d\n", $type, scalar @i; printf " %-11d %s\n", $_, $$h for @i; > Ubuntu Enable and Disable the Network Interface, The nmcli is a command-line utility that is used as a replacement for other graphical clients or nm-applet. Using the nmcli utility, you can display, create,
List Network Interfaces in Debian 10
As a system administrator or a normal user, you often need to perform network configurations. Before doing so, you should know how many network interfaces are available in your system. This article will discuss various ways to list network interfaces in Debian systems.
The commands listed in this article were run using the command-line Terminal application. To launch the Terminal application in Debian, click the Activities tab in the top left corner of the desktop and type terminal in the search bar . When the search result appears, click on the Terminal icon to open the Terminal.
Note: All the commands discussed in this article have been executed with the Debian 10 Buster system.
Method #1: IP Command
The most common and easiest way to list network interfaces is by using the IP command. This command provides a wide array of information about your system’s network interfaces.
To list the network interfaces in your system, issue the following command in Terminal:
The above command lists all the network interfaces available in your system. The above output shows that there are three interfaces in the system: one loopback interface (lo) and two Ethernet interfaces (eth0 and eth1) are listed, along with other statistics. This command will also show some other useful information about the network interfaces, including IP address, status (UP or DOWN), MAC address, etc.
Note: You may have different network interface names based on your system’s hardware.
You can also use the following IP command to list the network interfaces:
Method #2: ifconfig Command
The ifconfig command has now become obsolete but is still supported in many Linux distributions. You can use the ifconfig command to list the network interfaces available in your system.
Instead of typing ifconfig , type the command /sbin/ifconfig to list the network interfaces in your system.
In addition to listing the network interfaces, the above command will show other useful information about the network interfaces, including IP address, MTU size, number of sent/received packets, etc.
Method #3: netstat Command
The netstat command can also be used to list the network interfaces available in your system. To do so, type netstat , followed by the -i flag, as follows:
The above command lists the available network interfaces in your system, along with other useful information, such as the number of sent received packets, MTU size, etc.
Method #4: nmcli Command
The nmcli command also provides information about network interfaces. The nmcli command is available with Debian distributions that are running on GUI interfaces. However, if you are working on a non-GUI system, you will need to install the network manager using the following command in Terminal:
Once installation is complete, run the below commands in Terminal to enable and start the network manager:
To list the available network interfaces in your system, run the below command in Terminal:
The above command lists brief information about the available network interfaces.
Method #5: /sys/class/net Directory
You can also view network interfaces in your system by viewing the contents of the /sys/class/net directory. To do so, run the following command in Terminal:
The above command returns a concise output displaying only the names of the interfaces available in your system.
Method #6: /proc/net/dev File
The /proc/net/dev file also contains information about network interfaces. You can view the available network interfaces in your system by viewing the contents of this file. Run the following command in the Terminal to do so:
The above command lists the network interfaces available in the system, along with some other information about the interfaces.
Conclusion
The great thing about Linux is that it allows you to perform the same job in different ways. This article discussed various methods through which you can list the network interfaces in your Debian system.
Count network interfaces in Bash, This will pipe the output of ifconfig through grep, match all lines starting with the string tun (this is accomplished using the "anchor"
List only the device names of all available network interfaces
Another alternative would be:
Just use /sys/class/net and strip out the path:
$ basename -a /sys/class/net/* eth0 eth1 lo ppp0 tun0 A more modern way would be to use the iproute json output and a parser, like:
$ ip -j link |jq -r '.[].ifname' lo wlp0s20f3 enp0s31f6 virbr0 virbr0-nic Which allows you to filter out the loopback interface:
$ ip -j link |jq -r '.[].ifname | select(. != "lo")' wlp0s20f3 enp0s31f6 virbr0 virbr0-nic Bash - Shell - Get interface name of IP address, Does the command ifconfig show what you want? – Danizavtz. May 8, 2020 at 11:28 · Get the addresses of all the interfaces and see which one