Tom Browder:
# added alias IPv4s: up ip addr add 142.54.186.3/29 dev $IFACE label $IFACE:0 down ip addr del 142.54.186.3/29 dev $IFACE label $IFACE:0
Ironically, the "modern tools" aspect is the thing that you are in fact aiming to eliminate here. |/etc/network/interfaces| is best treated as an entirely descriptive mechanism, with as little imperative stuff in it as can be arranged. Here, you are getting rid of the imperative explicit invocations of the |ip| command, the "modern tool" as you mention, and replacing them with the descriptive "stanzas" that |/etc/network/interfaces| /already has/ as a mechanism for non-imperatively describing multiple IPv4/IPv6 addresses on a single |eth0| interface.
|ifup| and |ifdown| are best thought of as translators, as their manual page implies. They take what is in |/etc/network/interfaces| and translate it into the necessary sequences of imperative commands for actually doing the job, which they run under the covers. Those underlying commands can include |bootpc|, |avahi-autoipd|, |settle-dad.sh|, |pon|, |poff|, |wvdial|, |dhclient|, |dhclient3|, |pump|, |udhcpc|, |dhcpd|, |kill|, |ip|, and (sic!) |ifconfig|, all invoked with various parameters calculated from the |/etc/network/interfaces| description.
They aren't the only translators for that file. For example, here's what happens when one runs your proposed non-imperative |/etc/network/interfaces| (with the typing errors mentioned elsewhere cleaned up) through mine, which translates from that description <http://jdebp.eu./Softwares/nosh/guide/rcconf-amalgamation.html> into (roughly) the |rc.conf| configuration format for FreeBSD/TrueOS <https://www.freebsd.org/cgi/man.cgi?query=rc.conf>:
JdeBP % sudo redo -C /etc/system-control/convert/ rc.conf Password: redo: INFO: rc.conf: Redone. JdeBP % sed -ne '/etc.network.interfaces/,/sysrc:/p' /etc/system-control/convert/rc.conf # Converted from /etc/network/interfaces: network_interfaces="lo eth0 " ifconfig_lo="AUTO inet 127.0.0.1 " ifconfig_eth0="AUTO inet 142.54.186.2 netmask 255.255.255.248 gateway 142.54.186.1 " ifconfig_eth0_ipv6="inet6 2604:4300:a:95::2 netmask ffff:ffff:ffff:ffff:: " ifconfig_eth0_aliases="inet 142.54.186.3 inet 142.54.186.4 inet 142.54.186.5 inet 142.54.186.6 inet6 2604:4300:a:95::3 inet6 2604:4300:a:95::4 inet6 2604:4300:a:95::5 inet6 2604:4300:a:95::6" # dump by sysrc: JdeBP %
