[linux] pripojenie na server
Peter Farkas
peto.farkas na gmail.com
Pátek Září 9 11:12:27 CEST 2011
Ahoj,
On Friday 09 September 2011 06:44:20 Tomáš Lukala wrote:
> > > potreboval by som poradiť. Mám v správe jeden server ale už
> >
> > nie router
> >
> > > ktorým je server pripojený do sveta. Server je súčasťou vnútornej
> > > siete a beží na ňom file server a zopár ďalších služieb pre potreby
> > > vnútornej siete. Má privátni IP adresu.
> > >
> > > Potreboval by som sa na server pripojiť vzdialene,
> >
> > najlepšie pomocou ssh.
> >
> > > Poradí mi niekto ako na to keď server má privátnu IP?
> >
> > Existuje niekde
> >
> > > nejaký návod?
> >
> > autossh by ten problem na serveri za routerom nevyriesilo ?
> > viz http://www.harding.motd.ca/autossh/
>
> ako? jedine co ma napada je nechat bezat autossh s tym, ze bude dookola
> vyvolavat "ssh -R ..."
> a kontrolovat, ci bezi.
Pozri si manual pre autossh, text verzia je v prilohe.
Viz. DESCRIPTION
autossh is a program to start a copy of ssh and monitor it, restarting it
as necessary should it die or stop passing traffic.
Ja som to sice este nekonfiguroval ale pamatam si, ze ked sme to niekde
pouzivali tak sa to cez neprivilegovane konto a ssh pub kluc prihlasovalo na
nejaky server na internete. Z ktoreho sme sa potom cez 'ssh -p XXXXX
root na localhost' prihlasovali na ten server za firewallom.
>
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Peter
------------- další část ---------------
AUTOSSH(1) Gentoo General Commands Manual AUTOSSH(1)
[1mNAME[0m
[1mautossh [22m? monitor and restart ssh sessions
[1mSYNOPSIS[0m
[1mautossh [22m[[1m-V[22m] [[1m-M [4m[22mport[:echo_port][24m] [[1m-f[22m] [4m[SSH_OPTIONS][0m
[1mDESCRIPTION[0m
[1mautossh [22mis a program to start a copy of ssh and monitor it, restarting it
as necessary should it die or stop passing traffic.
The original idea and the mechanism were from rstunnel (Reliable SSH Tun?
nel). With version 1.2 of [1mautossh [22mthe method changed: [1mautossh [22muses ssh to
construct a loop of ssh forwardings (one from local to remote, one from
remote to local), and then sends test data that it expects to get back.
(The idea is thanks to Terrence Martin.)
With version 1.3, a new method is added (thanks to Ron Yorston): a port
may be specified for a remote echo service that will echo back the test
data. This avoids the congestion and the aggravation of making sure all
the port numbers on the remote machine do not collide. The loop-of -for?
wardings method remains available for situations where using an echo ser?
vice may not be possible.
[1mCONTROLLING SSH[0m
[1mSSH exits[0m
[1mautossh [22mtries to distinguish the manner of death of the ssh process it is
monitoring and act appropriately. The rules are:
1. If the ssh process exited normally (for example, someone typed
"exit" in an interactive session), [1mautossh [22mexits rather than
restarting;
2. If [1mautossh [22mitself receives a SIGTERM, SIGINT, or a SIGKILL sig?
nal, it assumes that it was deliberately signalled, and exits
after killing the child ssh process;
3. If [1mautossh [22mitself receives a SIGUSR1 signal, it kills the child
ssh process and starts a new one;
4. Periodically (by default every 10 minutes), [1mautossh [22mattempts to
pass traffic on the monitor forwarded port. If this fails,
[1mautossh [22mwill kill the child ssh process (if it is still running)
and start a new one;
5. If the child ssh process dies for any other reason, [1mautossh [22mwill
attempt to start a new one.
[1mStartup behaviour[0m
If the ssh session fails with an exit status of 1 on the very first try,
[1mautossh[0m
1. will assume that there is some problem with syntax or the connec?
tion setup, and will exit rather than retrying;
2. There is a "starting gate" time. If the first ssh process fails
within the first few seconds of being started, [1mautossh [22massumes
that it never made it "out of the starting gate", and exits. This
is to handle initial failed authentication, connection, etc. This
time is 30 seconds by default, and can be adjusted (see the
AUTOSSH_GATETIME environment variable below). If AUTOSSH_GATETIME
is set to 0, then both behaviours are disabled: there is no
"starting gate", and autossh will restart even if ssh fails on
the first run with an exit status of 1.
[1mContinued failures[0m
If the ssh connection fails and attempts to restart it fail in quick suc?
cession, [1mautossh [22mwill start delaying its attempts to restart, gradually
backing farther and farther off up to a maximum interval of the [1mautossh[0m
poll time (usually 10 minutes). [1mautossh [22mcan be "prodded" to retry by
signalling it, perhaps with SIGHUP ("kill -HUP").
[1mConnection setup[0m
As connections must be established unattended, the use of [1mautossh[0m
requires that some form of automatic authentication be set up. The use of
RSAAuthentication with ssh-agent is the recommended method. The example
wrapper script attempts to check if there is an agent running for the
current environment, and to start one if there isn't.
It cannot be stressed enough that you must make sure ssh works on its
own, that you can set up the session you want before you try to run it
under [1mautossh[0m
If you are tunnelling and using an older version of ssh that does not
support the [1m-N [22mflag, you should upgrade (your version has security
flaws). If you can't upgrade, you may wish to do as rstunnel does, and
give ssh a command to run, such as "sleep 99999999999".
[1mOPTIONS[0m
[1m-M [4m[22mport[:echo_port][0m
specifies the base monitoring port to use. Without the echo port,
this port and the port immediately above it ( [4mport[24m + 1) should be
something nothing else is using. [1mautossh [22mwill send test data on
the base monitoring port, and receive it back on the port above.
For example, if you specify "-M 20000", [1mautossh [22mwill set up for?
wards so that it can send data on port 20000 and receive it back
on 20001.
Alternatively, a port for a remote echo service may be specified.
This should be port 7 if you wish to use the standard inetd echo
service. When an echo port is specified, only the specified mon?
itor port is used, and it carries the monitor message in both
directions.
Many people disable the echo service, or even disable inetd, so
check that this service is available on the remote machine. Some
operating systems allow one to specify that the service only lis?
ten on the localhost (loopback interface), which would suffice
for this use.
The echo service may also be something more complicated: perhaps
a daemon that monitors a group of ssh tunnels.
Setting the monitor port to 0 turns the monitoring function off,
and autossh will only restart ssh upon ssh's exit. For example,
if you are using a recent version of OpenSSH, you may wish to
explore using the [1mServerAliveInterval [22mand [1mServerAliveCountMax[0m
options to have the SSH client exit if it finds itself no longer
connected to the server. In many ways this may be a better solu?
tion than the monitoring port.
[1m-f [22mcauses autossh to drop to the background before running ssh. The
[1m-f [22mflag is stripped from arguments passed to ssh. Note that there
is a crucial a difference between [1m-f [22mwith autossh, and [1m-f [22mwith
ssh: when used with [1mautossh [22mssh will be unable to ask for pass?
words or passphrases.
[1m-V [22mcauses [1mautossh [22mto display its version number and exit.
[1mENVIRONMENT[0m
Other than the flag to set the connection monitoring port, [1mautossh [22muses
environment variables to control features. ssh seems to be still collect?
ing letters for options, and this seems the easiest way to avoid colli?
sions.
AUTOSSH_DEBUG
If this variable is set, the logging level is set to to
LOG_DEBUG, and if the operating system supports it, syslog is set
to duplicate log entries to stderr.
AUTOSSH_FIRST_POLL
Specifies the time to wait before the first connection test.
Thereafter the general poll time is used (see AUTOSSH_POLL
below).
AUTOSSH_GATETIME
Specifies how long ssh must be up before we consider it a suc?
cessful connection. The default is 30 seconds. Note that if
AUTOSSH_GATETIME is set to 0, then not only is the gatetime be?
haviour turned off, but autossh also ignores the first run fail?
ure of ssh. This may be useful when running autossh at boot.
AUTOSSH_LOGLEVEL
Specifies the log level, corresponding to the levels used by sys?
log; so 0-7 with 7 being the chattiest.
AUTOSSH_LOGFILE
Specifies that [1mautossh [22mshould use the named log file, rather than
syslog.
AUTOSSH_MAXLIFETIME
Sets the maximum number of seconds that the program should run.
Once the number of seconds has been passed, the ssh child will be
killed and the program will exit.
AUTOSSH_MAXSTART
Specifies how many times ssh should be started. A negative number
means no limit on the number of times ssh is started. The default
value is -1.
AUTOSSH_MESSAGE
Append message to echo message sent when testing connections.
AUTOSSH_NTSERVICE
(Cygwin only.) When set to "yes" , autossh sets up to run as an
NT service under cygrunsrv. This adds the -N flag for ssh if not
already set, sets the log output to stdout, and changes the be?
haviour on ssh exit so that it will restart even on a normal
exit.
AUTOSSH_PATH
Specifies the path to the ssh executable, in case it is different
than the path compiled in.
AUTOSSH_PIDFILE
Write autossh pid to specified file.
AUTOSSH_POLL
Specifies the connection poll time in seconds; default is 600
seconds. If the poll time is less than twice the network time?
outs (default 15 seconds) the network timeouts will be adjusted
downward to 1/2 the poll time.
AUTOSSH_PORT
Sets the connection monitoring port. Mostly in case ssh appropri?
ates -M at some time. But because of this possible use,
AUTOSSH_PORT overrides the -M flag. A value of 0 turns the moni?
toring function off.
[1mAUTHOR[0m
[1mautossh [22mwas written by Carson Harding.
[1mSEE ALSO[0m
ssh(1), ssh-add(1), ssh-agent(1), ssh-keygen(1), cygrunsrv(1).
Gentoo/linux Jul 20, 2004 Gentoo/linux
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