Ubuntu Manpage: ifup - bring a network interface up

Provided by: ifupdown_0.8.36+nmu1ubuntu4_amd64

NAME

       ifup - bring a network interface up

       ifdown - take a network interface down

       ifquery - parse interface configuration

SYNOPSIS

       ifup  [-nv]  [--no-act] [--verbose] [-i FILE|--interfaces=FILE] [--state-dir=DIR] [--allow
       CLASS] -a|IFACE...
       ifup -h|--help
       ifup -V|--version

       ifdown [-nv] [--no-act] [--verbose] [-i FILE|--interfaces=FILE] [--state-dir=DIR] [--allow
       CLASS] -a|IFACE...

       ifquery  [-nv]  [--verbose]  [-i FILE|--interfaces=FILE] [--state-dir=DIR] [--allow CLASS]
       IFACE...

       ifquery -l|--list [-nv] [--verbose] [-i FILE|--interfaces=FILE] [--state-dir=DIR] [--allow
       CLASS] [-a|IFACE...]

       ifquery --state [--state-dir=DIR] [--allow CLASS] [-a|IFACE...]

DESCRIPTION

       The  ifup  and  ifdown  commands  may be used to configure (or, respectively, deconfigure)
       network interfaces based on interface definitions  in  the  file  /etc/network/interfaces.
       ifquery command may be used to parse interfaces configuration.

OPTIONS

A summary of options is included below.

-a, --all
If given to ifup, affect all interfaces marked auto. Interfaces are brought up in
the order in which they are defined in /etc/network/interfaces. Combined with
--allow, acts on all interfaces of a specified class instead. If given to ifdown,
affect all defined interfaces. Interfaces are brought down in the order in which
they are currently listed in the state file. Only interfaces defined in
/etc/network/interfaces will be brought down.

--force
Force configuration or deconfiguration of the interface.

--ignore-errors
If any of the commands of scripts fails, continue.

-h, --help
Show summary of options.

--allow=CLASS
Only allow interfaces listed in an allow-CLASS line in /etc/network/interfaces to
be acted upon.

-i FILE, --interfaces=FILE
Read interface definitions from FILE instead of from /etc/network/interfaces.

--state-dir=DIR
Keep interface state in DIR instead of in /run/network.

-X PATTERN, --exclude=PATTERN
Exclude interfaces from the list of interfaces to operate on by the PATTERN.
PATTERN uses a usual shell glob syntax. If shell wildcards are not used, it must
match the exact interface name. This option may be specified multiple times
resulting in more than one pattern being excluded.

-o OPTION=VALUE
Set OPTION to VALUE as though it were in /etc/network/interfaces.

-n, --no-act
Don't configure any interfaces or run any "up" or "down" commands.

--no-mappings
Don't run any mappings. See interfaces(5) for more information about the mapping
feature.

--no-scripts
Don't run any scripts under /etc/network/if-*.d/

--no-loopback
Disable special handling of the loopback interface. By default, the loopback
interface (lo on Linux) is predefined internally as an auto interface, so it's
brought up on ifup -a automatically. In the case the loopback device is redefined
by user, the interface is configured just once anyway. If, however, another
interface is also defined as loopback, it's configured as usual. Specifying this
option disables this behaviour, so the loopback interface won't be configured
automatically.

-V, --version
Show copyright and version information.

-v, --verbose
Show commands as they are executed.

-l, --list
For ifquery, list all the interfaces which match the specified class. If no class
specified, prints all the interfaces listed as auto.

--state
For ifquery, dump the state of the interfaces. When no interfaces specified, lists
all interfaces brought up together with logical interfaces assigned to them and
exits with a status code indicating success. If one or more interfaces specified,
display state of these interfaces only; successful code is returned if all of
interfaces given as arguments are up. Otherwise, 0 is returned.

EXAMPLES

       ifup -a
              Bring up all the interfaces defined with auto in /etc/network/interfaces

       ifup eth0
              Bring up interface eth0

       ifup eth0=home
              Bring up interface eth0 as logical interface home

       ifdown -a
              Bring down all interfaces that are currently up.

       ifquery -l
              Print names of all interfaces specified with the auto keyword.

       ifquery -l --allow=hotplug
              Print names of all interfaces specified with the allow-hotplug keyword.

       ifquery eth0
              Display the interface options as specified in the ifupdown configuration. Each key-
              value pair is printed out on individual line using ": " as separator.

NOTES

       ifup, ifdown, and ifquery are actually the same program called by different names.

       The  program  does  not configure network interfaces directly; it runs low level utilities
       such as ip to do its dirty work.

       When invoked, ifdown checks if ifup is still running. In that case,  SIGTERM  is  sent  to
       ifup.

       During interface deconfiguration, ifdown ignores errors the same way as if --ignore-errors
       was specified.

FILES

       /etc/network/interfaces
              definitions of network interfaces See interfaces(5) for more information.

       /run/network/ifstate
              current state of network interfaces

CONCURRENCY

       Ifupdown uses per-interface locking to ensure that concurrent ifup and ifdown calls to the
       same  interface are run in serial.  However, calls to different interfaces will be able to
       run in parallel.

EXIT STATUS

       For ifup and ifdown, the exit status will be 0 if the given  interface(s)  have  all  been
       (de)configured  successfully,  1  if there was any error.  The result of these commands is
       idempotent; running ifup on an interface that is already up will result in an exit  status
       of  0,  and similarly running ifdown on an interface that is not up will also result in an
       exit status of 0.

       ifquery will normally return with exit status 0 if an  interface  with  a  matching  iface
       stanza,  1  if  there  is  no matching stanza.  ifquery --state will also return with exit
       status 1 if the given interface was known but was not up.

KNOWN BUGS/LIMITATIONS

       The program keeps records of whether network interfaces are up or down.  Under exceptional
       circumstances  these  records  can  become  inconsistent  with  the  real  states  of  the
       interfaces.  For  example,  an  interface  that  was  brought  up  using  ifup  and  later
       deconfigured  using  ifconfig  will  still be recorded as up.  To fix this you can use the
       --force option to force ifup or ifdown to run configuration  or  deconfiguration  commands
       despite what it considers the current state of the interface to be.

       The  file  /run/network/ifstate  must be writable for ifup or ifdown to work properly.  If
       that location is not writable (for example, because the root filesystem is  mounted  read-
       only  for  system  recovery) then /run/network/ifstate should be made a symbolic link to a
       writable location.  If that is not possible then you can use the  --force  option  to  run
       configuration or deconfiguration commands without updating the file.

       Note  that the program does not run automatically: ifup alone does not bring up interfaces
       that appear as a result of hardware being installed and ifdown alone does not  bring  down
       interfaces  that  disappear  as  a  result  of  hardware  being  removed.  To automate the
       configuration of network interfaces you need to install other packages such as udev(7)  or
       ifplugd(8).

AUTHORS

       The  ifupdown  suite  was  created  by  Anthony  Towns <aj@azure.humbug.org.au>, currently
       maintained   by   Santiago   Ruano   Rincón   <santiago@debian.org>   and   Josue   Ortega
       <josue@debian.org>

       Many      others      have      helped     develop     ifupdown     over     time,     see
       /usr/share/doc/ifupdown/changelog.Debian.gz for a full history.