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what's the right way to resolve localhost's IPs

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  what's the right way to resolve localhost's IPs fh@dnsbed.com - 2023-03-22 02:20 +0100
    Re: what's the right way to resolve localhost's IPs Jeremy Ardley <jeremy@ardley.org> - 2023-03-22 03:10 +0100
      Re: what's the right way to resolve localhost's IPs fh@dnsbed.com - 2023-03-22 03:40 +0100
      Re: what's the right way to resolve localhost's IPs Gregory Seidman <gsslist+debian@anthropohedron.net> - 2023-03-22 21:40 +0100
      Re: what's the right way to resolve localhost's IPs Tom Furie <tom@furie.org.uk> - 2023-03-22 22:20 +0100
        Re: what's the right way to resolve localhost's IPs Greg Wooledge <greg@wooledge.org> - 2023-03-22 22:50 +0100
          Re: what's the right way to resolve localhost's IPs Jeremy Ardley <jeremy@ardley.org> - 2023-03-23 00:10 +0100
            Re: what's the right way to resolve localhost's IPs Greg Wooledge <greg@wooledge.org> - 2023-03-23 00:40 +0100
              Re: what's the right way to resolve localhost's IPs Jeremy Ardley <jeremy@ardley.org> - 2023-03-23 01:00 +0100
                Re: what's the right way to resolve localhost's IPs Nicolas George <george@nsup.org> - 2023-03-23 08:50 +0100
                  Re: what's the right way to resolve localhost's IPs Jeremy Ardley <jeremy@ardley.org> - 2023-03-23 09:00 +0100
                  Re: what's the right way to resolve localhost's IPs Lee <ler762@gmail.com> - 2023-03-23 12:00 +0100
    Re: what's the right way to resolve localhost's IPs Emanuel Berg <incal@dataswamp.org> - 2023-03-30 07:50 +0200
      Re: what's the right way to resolve localhost's IPs fh@dnsbed.com - 2023-03-30 10:10 +0200

#256258 — what's the right way to resolve localhost's IPs

Hello,

In my shell script, how to get the localhost's IPs (eth0 and eth1) 
correctly?
I know I can run 'ifconfig' and grep etc, but it's maybe not that 
graceful.

Thanks
Corey

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#256259

On 22/3/23 09:12, fh@dnsbed.com wrote:
> Hello,
>
> In my shell script, how to get the localhost's IPs (eth0 and eth1) 
> correctly?
> I know I can run 'ifconfig' and grep etc, but it's maybe not that 
> graceful.

On Debian the preferred  command is

root@debian12:~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
group default qlen 1000
     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
     inet 127.0.0.1/8 scope host lo
        valid_lft forever preferred_lft forever
     inet6 ::1/128 scope host
        valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel 
state UP group default qlen 1000
     link/ether 08:00:27:18:b6:ac brd ff:ff:ff:ff:ff:ff
     inet 10.31.40.166/24 brd 10.31.40.255 scope global dynamic enp0s3
        valid_lft 81816sec preferred_lft 81816sec
     inet6 2403:5800:c101:b700:a00:27ff:fe18:b6ac/64 scope global 
dynamic mngtmpaddr
        valid_lft 6667sec preferred_lft 3066sec
     inet6 fe80::a00:27ff:fe18:b6ac/64 scope link
        valid_lft forever preferred_lft forever

You can also output in .json format

root@debian12:~# ip -j a
[{"ifindex":1,"ifname":"lo","flags":["LOOPBACK","UP","LOWER_UP"],"mtu":65536,"qdisc":"noqueue","operstate":"UNKNOWN","group":"default","txqlen":1000,"link_type":"loopback","address":"00:00:00:00:00:00","broadcast":"00:00:00:00:00:00","addr_info":[{"family":"inet","local":"127.0.0.1","prefixlen":8,"scope":"host","label":"lo","valid_life_time":4294967295,"preferred_life_time":4294967295},{"family":"inet6","local":"::1","prefixlen":128,"scope":"host","valid_life_time":4294967295,"preferred_life_time":4294967295}]},{"ifindex":2,"ifname":"enp0s3","flags":["BROADCAST","MULTICAST","UP","LOWER_UP"],"mtu":1500,"qdisc":"fq_codel","operstate":"UP","group":"default","txqlen":1000,"link_type":"ether","address":"08:00:27:18:b6:ac","broadcast":"ff:ff:ff:ff:ff:ff","addr_info":[{"family":"inet","local":"10.31.40.166","prefixlen":24,"broadcast":"10.31.40.255","scope":"global","dynamic":true,"label":"enp0s3","valid_life_time":81787,"preferred_life_time":81787},{"family":"inet6","local":"2403:5800:c101:b700:a00:27ff:fe18:b6ac","prefixlen":64,"scope":"global","dynamic":true,"mngtmpaddr":true,"valid_life_time":6638,"preferred_life_time":3037},{"family":"inet6","local":"fe80::a00:27ff:fe18:b6ac","prefixlen":64,"scope":"link","valid_life_time":4294967295,"preferred_life_time":4294967295}]}]

and if you write a script like this (and make it write protected and 
executable)

  cat ipv4_addresses.py
#!/usr/bin/env python3
import json
import sys

data = sys.stdin.read()

interfaces = json.loads(data)

for interface in interfaces:
     ifname = interface['ifname']
     for addr_info in interface['addr_info']:
         if addr_info['family'] == 'inet':
             ipv4 = addr_info['local']
             print(f"{ifname}: {ipv4}")

you can do

ip -j a | ./ipv4_addresses.py
lo: 127.0.0.1
enp7s0: 10.31.40.68

or on a fancier setup

ip -j a | ./ipv4_addresses.py
lo: 127.0.0.1
eth0: 10.31.40.4
eth0: 10.31.40.5
eth0: 10.31.40.101
docker0: 172.17.0.1


> -- 

Jeremy
(Lists)

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#256260

On 2023-03-22 10:06, Jeremy Ardley wrote:
> On 22/3/23 09:12, fh@dnsbed.com wrote:
>> Hello,
>> 
>> In my shell script, how to get the localhost's IPs (eth0 and eth1) 
>> correctly?
>> I know I can run 'ifconfig' and grep etc, but it's maybe not that 
>> graceful.
> 
> On Debian the preferred  command is
> 
> root@debian12:~# ip a
> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
> group default qlen 1000
>     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>     inet 127.0.0.1/8 scope host lo
>        valid_lft forever preferred_lft forever
>     inet6 ::1/128 scope host
>        valid_lft forever preferred_lft forever
> 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel 
> state UP group default qlen 1000
>     link/ether 08:00:27:18:b6:ac brd ff:ff:ff:ff:ff:ff
>     inet 10.31.40.166/24 brd 10.31.40.255 scope global dynamic enp0s3
>        valid_lft 81816sec preferred_lft 81816sec
>     inet6 2403:5800:c101:b700:a00:27ff:fe18:b6ac/64 scope global 
> dynamic mngtmpaddr
>        valid_lft 6667sec preferred_lft 3066sec
>     inet6 fe80::a00:27ff:fe18:b6ac/64 scope link
>        valid_lft forever preferred_lft forever
> 
> You can also output in .json format
> 
> root@debian12:~# ip -j a
>
[{"ifindex":1,"ifname":"lo","flags":["LOOPBACK","UP","LOWER_UP"],"mtu":65536,"qdisc":"noqueue","operstate":"UNKNOWN","group":"default","txqlen":1000,"link_type":"loopback","address":"00:00:00:00:00:00","broadcast":"00:00:00:00:00:00","addr_info":[{"family":"inet","local":"127.0.0.1","prefixlen":8,"scope":"host","label":"lo","valid_life_time":4294967295,"preferred_life_time":4294967295},{"family":"inet6","local":"::1","prefixlen":128,"scope":"host","valid_life_time":4294967295,"preferred_life_time":4294967295}]},{"ifindex":2,"ifname":"enp0s3","flags":["BROADCAST","MULTICAST","UP","LOWER_UP"],"mtu":1500,"qdisc":"fq_codel","operstate":"UP","group":"default","txqlen":1000,"link_type":"ether","address":"08:00:27:18:b6:ac","broadcast":"ff:ff:ff:ff:ff:ff","addr_info":[{"family":"inet","local":"10.31.40.166","prefixlen":24,"broadcast":"10.31.40.255","scope":"global","dynamic":true,"label":"enp0s3","valid_life_time":81787,"preferred_life_time":81787},{"family":"inet6","local":"2403:5800:c101:
b700:a00:27ff:fe18:b6ac","prefixlen":64,"scope":"global","dynamic":true,"mngtmpaddr":true,"valid_life_time":6638,"preferred_life_time":3037},{"family":"inet6","local":"fe80::a00:27ff:fe18:b6ac","prefixlen":64,"scope":"link","valid_life_time":4294967295,"preferred_life_time":4294967295}]}]
> 
> and if you write a script like this (and make it write protected and 
> executable)
> 
>  cat ipv4_addresses.py
> #!/usr/bin/env python3
> import json
> import sys
> 
> data = sys.stdin.read()
> 
> interfaces = json.loads(data)
> 
> for interface in interfaces:
>     ifname = interface['ifname']
>     for addr_info in interface['addr_info']:
>         if addr_info['family'] == 'inet':
>             ipv4 = addr_info['local']
>             print(f"{ifname}: {ipv4}")
> 
> you can do
> 
> ip -j a | ./ipv4_addresses.py
> lo: 127.0.0.1
> enp7s0: 10.31.40.68
> 
> or on a fancier setup
> 

Thanks a lot. Now I prefer this way:
$ ip -j a|python3 -mjson.tool

regards.

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#256276

On Wed, Mar 22, 2023 at 10:06:40AM +0800, Jeremy Ardley wrote:
> 
> On 22/3/23 09:12, fh@dnsbed.com wrote:
> > Hello,
> > 
> > In my shell script, how to get the localhost's IPs (eth0 and eth1)
> > correctly?
> > I know I can run 'ifconfig' and grep etc, but it's maybe not that
> > graceful.
> 
> On Debian the preferred  command is
> 
> root@debian12:~# ip a
[...]
> You can also output in .json format
> 
> root@debian12:~# ip -j a
[...]
> 
> and if you write a script like this (and make it write protected and
> executable)
[...]

For those of us who like using jq for this kind of thing:

#!/bin/sh

ip -j a | jq -r '
	.[] | {
		"name": .ifname,
		"addr": .addr_info |
			map(select(.family ==  "inet")) |
			.[0].local
	} |
	select(.addr) |
	.name + ": " + .addr'

> you can do
> 
> ip -j a | ./ipv4_addresses.py
> lo: 127.0.0.1
> enp7s0: 10.31.40.68
> 
> or on a fancier setup
> 
> ip -j a | ./ipv4_addresses.py
> lo: 127.0.0.1
> eth0: 10.31.40.4
> eth0: 10.31.40.5
> eth0: 10.31.40.101
> docker0: 172.17.0.1
> 
> > -- 
> 
> Jeremy
> (Lists)
--Gregory

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#256278

[Multipart message — attachments visible in raw view] — view raw

On Wed, Mar 22, 2023 at 10:06:40AM +0800, Jeremy Ardley wrote:
> You can also output in .json format
> 
> root@debian12:~# ip -j a
> [{"ifindex":1,"ifname":"lo","flags":["LOOPBACK","UP","LOWER_UP"],"mtu":65536,"qdisc":"noqueue","operstate":"UNKNOWN","group":"default","txqlen":1000,"link_type":"loopback","address":"00:00:00:00:00:00","broadcast":"00:00:00:00:00:00","addr_info":[{"family":"inet","local":"127.0.0.1","prefixlen":8,"scope":"host","label":"lo","valid_life_time":4294967295,"preferred_life_time":4294967295},{"family":"inet6","local":"::1","prefixlen":128,"scope":"host","valid_life_time":4294967295,"preferred_life_time":4294967295}]},{"ifindex":2,"ifname":"enp0s3","flags":["BROADCAST","MULTICAST","UP","LOWER_UP"],"mtu":1500,"qdisc":"fq_codel","operstate":"UP","group":"default","txqlen":1000,"link_type":"ether","address":"08:00:27:18:b6:ac","broadcast":"ff:ff:ff:ff:ff:ff","addr_info":[{"family":"inet","local":"10.31.40.166","prefixlen":24,"broadcast":"10.31.40.255","scope":"global","dynamic":true,"label":"enp0s3","valid_life_time":81787,"preferred_life_time":81787},{"family":"inet6","local":"2403:5800:c101:b700:a00:27ff:fe18:b6ac","prefixlen":64,"scope":"global","dynamic":true,"mngtmpaddr":true,"valid_life_time":6638,"preferred_life_time":3037},{"family":"inet6","local":"fe80::a00:27ff:fe18:b6ac","prefixlen":64,"scope":"link","valid_life_time":4294967295,"preferred_life_time":4294967295}]}]
> 
> and if you write a script like this (and make it write protected and
> executable)

Or...

ip -o a | awk '{print $2, $4}'

Cheers,
Tom

-- 
My mother is a fish.
		-- William Faulkner

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#256279

On Wed, Mar 22, 2023 at 09:16:48PM +0000, Tom Furie wrote:
> Or...
> 
> ip -o a | awk '{print $2, $4}'

I think they wanted to restrict it to IPv4 (inet) addresses, and omit
the netmask (/8 or whatever CIDR suffix), so:

ip -o a | awk -F '[ /]*' '$3 == "inet" {print $2, $4}'

But... again... why the hell would someone WANT THIS OUTPUT?  What is
it going to be use-- wait.  I remember now.  One of the posters in
this thread, I think not the OP, had the word "docker" in their
results.  So, there's no point asking any further.  Docker questions
that involve shell programming are never to be entertained.  It leads
only to increased misery, and never increased understanding.

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#256282

On 23/3/23 05:47, Greg Wooledge wrote:
> On Wed, Mar 22, 2023 at 09:16:48PM +0000, Tom Furie wrote:
>> Or...
>>
>> ip -o a | awk '{print $2, $4}'
> I think they wanted to restrict it to IPv4 (inet) addresses, and omit
> the netmask (/8 or whatever CIDR suffix), so:
>
> ip -o a | awk -F '[ /]*' '$3 == "inet" {print $2, $4}'
>
> But... again... why the hell would someone WANT THIS OUTPUT?  What is
> it going to be use-- wait.  I remember now.  One of the posters in
> this thread, I think not the OP, had the word "docker" in their
> results.  So, there's no point asking any further.  Docker questions
> that involve shell programming are never to be entertained.  It leads
> only to increased misery, and never increased understanding.
>
I am the guilty party who had docker. I have not raised any issue about it. The instance is not used any more and was an experiment in running nextcloud on an arm server

docker ps -a
CONTAINER ID   IMAGE               COMMAND                  CREATED       STATUS                   PORTS     NAMES
56a238ff2cbf   arm64v8/nextcloud   "/entrypoint.sh apac…"   2 years ago   Exited (0) 2 years ago             nextcloud

In rare circumstances I will use a docker version of a package if the Debian verion is not up to date, or I don't want the pain of compiling it, or if there is no easy way to compile a specific version to use with my version of Debian.

If I have to use a packaged application I will try and use an appimage

-- 
Jeremy
(Lists)

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#256283

On Thu, Mar 23, 2023 at 07:06:55AM +0800, Jeremy Ardley wrote:
> I am the guilty party who had docker. I have not raised any issue about it. The instance is not used any more and was an experiment in running nextcloud on an arm server

Then perhaps you can enlighten me: why does anyone (Docker user or
otherwise) need to write a shell script to list the IPv4 addresses
of the local system's network interfaces?

I can't think of any reasons other than "I want to update dynamic DNS"
(for which a dhclient hook is better suited, with the new IP address
being supplied in the environment), or "I need to use it to set up
firewall rules", a topic with which I'll admit I'm not very experienced,
but which doesn't seem particularly important on exposed servers.  I
would think you'd simply shut down all the services you don't want
running, rather than leaving them in place but trying to block them
with a firewall.

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#256285

On 23/3/23 07:33, Greg Wooledge wrote:
> On Thu, Mar 23, 2023 at 07:06:55AM +0800, Jeremy Ardley wrote:
>> I am the guilty party who had docker. I have not raised any issue about it. The instance is not used any more and was an experiment in running nextcloud on an arm server
> Then perhaps you can enlighten me: why does anyone (Docker user or
> otherwise) need to write a shell script to list the IPv4 addresses
> of the local system's network interfaces?
>
> I can't think of any reasons other than "I want to update dynamic DNS"
> (for which a dhclient hook is better suited, with the new IP address
> being supplied in the environment), or "I need to use it to set up
> firewall rules", a topic with which I'll admit I'm not very experienced,
> but which doesn't seem particularly important on exposed servers.  I
> would think you'd simply shut down all the services you don't want
> running, rather than leaving them in place but trying to block them
> with a firewall.
>
I am not the op. I mistakenly used an old server to illustrate how to 
extract ip addresses and it just happened it had been used once to run 
nextcloud in docker.

On your second topic I don't usually run firewalls on my cloud severs. 
In the AWS case they do it for you and in the linode case I just run the 
minimum services required.

-- 
Jeremy
(Lists)

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#256288

Jeremy Ardley (12023-03-23):
> On your second topic I don't usually run firewalls on my cloud severs.

But surely on a server the network configuration is static, including
the firewall rules, isn't it?

(Please imagine this mail set up on the Anakin/Padme meme template.)

Regards,

-- 
  Nicolas George

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#256289

On 23/3/23 15:42, Nicolas George wrote:
> Jeremy Ardley (12023-03-23):
>> On your second topic I don't usually run firewalls on my cloud severs.
> But surely on a server the network configuration is static, including
> the firewall rules, isn't it?
>
On AWS the firewall rules are set by AWS themselves, though there is a 
console to adjust them. I normally only open up the incoming ports I am 
using. For ssh I only allow it from my personal IPv4 and IPv6 ranges

On Linode I just run bare with no firewall and only trusted services 
listening on a few ports. Linode do block outgoing port 25 and 485.

In a better world, in case my server were to be compromised, I'd set up 
to manage my outgoing such as rate limiting outgoing DNS requests and 
blocking other destination ports entirely.

I'm sure there is a list of destination ports this applies to?

-- 
Jeremy
(Lists)

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#256293

On 3/23/23, Nicolas George <george@nsup.org> wrote:
> Jeremy Ardley (12023-03-23):
>> On your second topic I don't usually run firewalls on my cloud severs.
>
> But surely on a server the network configuration is static, including
> the firewall rules, isn't it?

Consider the IP addressing info coming from DHCP.  The network
configuration stays the same but the IP(v6)? address might change.

For example, Verizon is my ISP; they delegate a /56 to my router and
the router delegates /64's to the LANs.  I've got DHCP configured to
give out static host addresses to the various machines but the network
portion of the ipv6 address does change at Verizon's whim .. which
requires firewall rule changes because I haven't figured out how to
automatically plug in the newly delegated /64 into the firewall rules
for that lan :(

Regards,
Lee

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#256534

fh wrote:

> In my shell script, how to get the localhost's IPs (eth0 and
> eth1) correctly? I know I can run 'ifconfig' and grep etc,
> but it's maybe not that graceful.

Here is what I do, now idea if it's a good idea but maybe it
can help:

#! /bin/zsh
#
# this file:
#   https://dataswamp.org/~incal/conf/.zsh/ip

public-ip () {
    local name=$funcstack[1]
    local url='http://checkip.amazonaws.com'
    local open_dns=opendns.com
    echo $(curl --no-progress-meter $url) "($name)"
    dig +short myip.${open_dns} @resolver1.${open_dns}
}

inet () {
    local name=$funcstack[1]
    echo $(hostname -I | awk '{print $1}') "($name)"
    ifconfig $net | awk '/mask/{print $2}'
    ip addr show $net | awk '/inet /{print $2}' | cut -d '/' -f 1
}

list-ip () {
    public-ip
    inet
}
alias lip=list-ip

# $ lip
# 92.34.142.23
# 92.34.142.23
# 192.168.10.224
# 192.168.10.224
# 192.168.10.224

-- 
underground experts united
https://dataswamp.org/~incal

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#256536

On 2023-03-30 13:38, Emanuel Berg wrote:
> fh wrote:
> 
>> In my shell script, how to get the localhost's IPs (eth0 and
>> eth1) correctly? I know I can run 'ifconfig' and grep etc,
>> but it's maybe not that graceful.
> 
> Here is what I do, now idea if it's a good idea but maybe it
> can help:
> 
> #! /bin/zsh
> #
> # this file:
> #   https://dataswamp.org/~incal/conf/.zsh/ip
> 
> public-ip () {
>     local name=$funcstack[1]
>     local url='http://checkip.amazonaws.com'
>     local open_dns=opendns.com
>     echo $(curl --no-progress-meter $url) "($name)"
>     dig +short myip.${open_dns} @resolver1.${open_dns}
> }
> 
> inet () {
>     local name=$funcstack[1]
>     echo $(hostname -I | awk '{print $1}') "($name)"
>     ifconfig $net | awk '/mask/{print $2}'
>     ip addr show $net | awk '/inet /{print $2}' | cut -d '/' -f 1
> }
> 
> list-ip () {
>     public-ip
>     inet
> }
> alias lip=list-ip
> 
> # $ lip
> # 92.34.142.23
> # 92.34.142.23
> # 192.168.10.224
> # 192.168.10.224
> # 192.168.10.224


i like the JSON output just b/c I am a programmer knowing JSON pretty 
well. :)

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