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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-10 20:49:53 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-10 20:49:53 +0000 |
commit | 87aefc960557c2fb6fdf9ea4c1ac0e7983f68f68 (patch) | |
tree | 263fc56d7d40512aaa09193905008a3f4e3b0018 /debian/udev.README.Debian | |
parent | Adding upstream version 255.4. (diff) | |
download | systemd-87aefc960557c2fb6fdf9ea4c1ac0e7983f68f68.tar.xz systemd-87aefc960557c2fb6fdf9ea4c1ac0e7983f68f68.zip |
Adding debian version 255.4-1.debian/255.4-1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | debian/udev.README.Debian | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/debian/udev.README.Debian b/debian/udev.README.Debian new file mode 100644 index 0000000..dfe1fb4 --- /dev/null +++ b/debian/udev.README.Debian @@ -0,0 +1,150 @@ +This documents udev integration Debian specifics. Please see man udev(7) and +its referenced manpages for general documentation. + +Network interface naming +~~~~~~~~~~~~~~~~~~~~~~~~ +Since version 197 udev has a builtin persistent name generator which checks +firmware/BIOS provided index numbers or slot names (similar to biosdevname), +falls back to slot names (PCI numbers, etc., in the spirit of +/dev/disks/by-path/), and then optionally falls back to MAC address, and +generates names based on these properties. This provides "location oriented" +names for PCI cards such as "enp0s1" for ethernet, or wlp1s0" for a WIFI card +so that replacing a broken network card does not change the name (as long +as the new card is fitted into the bus in the old card's slot.) As location +based naming does not work well for USB devices, these use a MAC based naming +schema (see /lib/systemd/network/73-usb-net-by-mac.link). + +This has been enabled by default since udev 220-7, which affects new +installations/hardware. Existing installations/hardware which already got +covered by the old 75-persistent-net-generator.rules may keep their existing +interface names until the release of Debian 10 / Ubuntu 18.04 LTS; see +below. + +You can disable these stable names and go back to the kernel-provided ones +(which don't have a stable order) in one of two ways: + + - Put "net.ifnames=0" into the kernel command line (e. g. in + /etc/default/grub's GRUB_CMDLINE_LINUX_DEFAULT, then run "update-grub"). + + - Disable the default *.link rules with + "ln -s /dev/null /etc/systemd/network/99-default.link" + "ln -s /dev/null /etc/systemd/network/73-usb-net-by-mac.link" + and rebuild the initrd with "update-initramfs -u". + +See this page for more information: +http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/ + +Legacy persistent network interface naming +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Debian releases up to 8 ("Jessie") and Ubuntu up to 15.04 had an udev rule +/lib/udev/rules.d/75-persistent-net-generator.rules which fixed the name of a +network interface that it got when its MAC address first appeared in a +dynamically created /etc/udev/rules.d/70-persistent-net.rules file. + +This had inherent race conditions (which sometimes caused collisions and +interface names like "rename1"), required having to write state into /etc +(which isn't possible for read-only root), and did not work in virtualized +environments. + +This old schema is deprecated in Debian 9 ("Stretch"), and will not +be supported any more in Debian 10. + +Migration to the current network interface naming scheme +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Interface names must be be manually migrated to the new naming scheme before +upgrading to Debian 10 / Ubuntu 18.04 LTS. If you rely on the old names in +custom ifupdown stanzas, firewall scripts, or other networking configuration, +these will eventually need to be updated to the new names. + +WARNING: This process may render your machine inaccessible through ssh. Be sure +to have physical or serial console access to the machine or a way to revert to +your existing configuration. + +First, determine all relevant network interface names: those in +/etc/udev/rules.d/70-persistent-net.rules, or if that does not exist (in +the case of virtual machines), in "ip link" or /sys/class/net/. + +Then for every interface name use a command like + + grep -r eth0 /etc + +to find out where it is being used. + +Then on "real hardware" machines, rename the file to +70-persistent-net.rules.old; alternately, if you have multiple interfaces, +instead of renaming you may wish to comment out specific lines to convert a +single interface at a time. + +On VMs remove the files /etc/systemd/network/99-default.link and +/etc/systemd/network/50-virtio-kernel-names.link (the latter only exists on VMs +that use virtio network devices). + +Rebuild the initrd with + + update-initramfs -u + +and reboot. Then your system should have a new network interface name (or +names). Adjust configuration files as discovered with the grep above, and test +your system. + +Repeat for each network interface name, as necessary. + +Custom net interface naming +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +In some cases it is convenient to define your own specific names for network +interfaces. These can be customized in two different ways: + + * You can create your own names via *.link files (see systemd.link(5)) based + on hardware properties. For example, /etc/systemd/network/10-dmz.link: + + ------------ snip ------------ + [Match] + MACAddress=11:22:aa:bb:cc:33 + + [Link] + Name=eth-dmz + ------------ snip ------------ + + * If you need attributes that link files don't expose, or you need more + powerful pattern matching, you can create udev rules (see udev(7)) + like /etc/udev/rules.d/76-netnames.rules: + + ------------ snip ------------ + # identify by vendor/model ID + SUBSYSTEM=="net", ACTION=="add", ENV{ID_VENDOR_ID}=="0x8086", \ + ENV{ID_MODEL_ID}=="0x1502", NAME="eth-intel-gb" + + # USB device by path + # get ID_PATH if not present yet + ENV{ID_PATH}=="", IMPORT{builtin}="path_id" + SUBSYSTEM=="net", ACTION=="add", ENV{ID_PATH}=="*-usb-0:3:1*", NAME="eth-blue-hub" + ------------ snip ---------- + + The name of the rules file needs to have a prefix smaller than "80" so that + it runs before /lib/udev/rules.d/80-net-setup-link.rules, and should have a + prefix bigger than "75" so that it runs after 75-net-description.rules and + thus you can use matches on ID_VENDOR and similar properties. + + * Unless you disabled net.ifnames, you can change the policy + (kernel/bios/path/MAC based naming) in an /etc/systemd/network/*.link file, + for individual devices or entire device classes. See man systemd.link(5) for + details about this. /lib/systemd/network/99-default.link is the default + policy. Note that /lib/systemd/network/73-usb-net-by-mac.link uses MAC based + names for USB devices. + +Any of the above changes require an initrd update with "update-initramfs -u" to +get effective. + +Using udev with LDAP or NIS +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +If the rules files reference usernames or groups not present in the +/etc/{passwd,group} files and the system is configured to use a +network-based database like LDAP or NIS then udev may fail at boot time +because users and groups are looked up well before the network has been +initialized. +A possible solution is to configure /etc/nsswitch.conf like this: + + passwd: files ldap [UNAVAIL=return] + group: files ldap [UNAVAIL=return] + +The nsswitch.conf syntax is documented in the glibc manual. |