MediaWiki-API-Ergebnis

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            "*": "Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."
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            "84": {
                "pageid": 84,
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                "title": "Remote Access",
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                        "*": "== Goal == \nYou might want to use our pool infrastructure - which means any pool client <tt>c001.cip.loc</tt> etc. - from a remote location, for example from home. This is totally fine!\n\n== Strategy ==\n\n; [[Shell]]: shell.stud.informatik.uni-goettingen.de - usable by every student. These machines are powerful enough to ''not'' require you to hop forward to a physical pool client machine.\n\n; login.informatik.uni-goettingen.de: usable ''only'' by staff members with [[Gwdg]]-Account\n\nYou ''might'' use those login machines as a gateway from the outside world into the pool - basically to any computer <tt>c001</tt> to <tt>c048</tt>. \n\nThis gateway approach is necessary as the pool computers have local, non-routeable IP-addresses like 172.27.x.y.\n\nFor accomplishing access to a pool machine you need to \"hop\" forward one time. On login you'll see a list of currently running computers. E.g.:\n\n System load of less used clients:\n c011          up      16:01,     0 users,  load 0.00, 0.01, 0.05\n c018          up      15:46,     0 users,  load 0.00, 0.01, 0.05\n\nSimply jump to any of them. \"<tt>ssh c011</tt>\" would work in this example.\n\n'''Hint:''' ''If you know the target machine already'' you might combine these two separate into a single one --> [[Remote Access/Single Command]] \n\nUsually the computers in the pool shutdown itself when nobody is logged in. To supply some computers to the above user several pool computers are running continuously to be reachable for this specific use case. This is: '''c031..c036''' which can be found in the first row in room [[-1.101]]. These computers are usable locally also without limitation. If they are in use in the very moment when you login remotely they may not be listed as available because of this very fact.\n\nPlease note that these clients reboot automatically early in the morning to clean up things - but only if nobody is logged in...\n\n== Problems with shared resources ==\n\nSystem resources are limited, those login machines are a shared source in more intense way than those pool computers are. \n\nIt is considered unfriendly behavior to stress a shared resource in such a manner that other users can not work anymore.\n\nOne usual trigger element for this kind or problems is [[Java]]. \n* Sometimes it crashes and does not clean up the allocated memory nor CPU resources. Just a very few Java processes hanging in the background can render that machine unusable - it has to get restarted with a hard reset. (Of course other languages allow generating the same problem, but we see Java most of the time...)\n* when you use [[Eclipse]] you might start background processes. Make sure to stop all of them...\n\n=== Killing a problematic process ===\nIf you have the suspicion that you have produced such bad background processes do the following:\n\nFirst get a terminal with <tt>top</tt> running\n* inside the working Desktop Environment: use a normal GUI-Terminal window to start <tt>top</tt>. How to do this depends on the Desktop Environment used. Usually there is a way to enter a command. Simply run <tt>top</tt>\n\nAlternatively go to a \"classic\" physical console. This does also work very often if the GUI is not usable for some reason.\n* log off (if possible)\n* go to a normal console - press <tt>CTRL-ALT-F2</tt> (or F1/F3/F4/F5/F6)\n* login\n* run <tt>[[top]]</tt>\n\nIn that Terminal:\n* use <tt>[[top]]</tt> to examine the running processes. For example look for \"java\" in the \"command\" column\n* note that the first column shows the process number\n* the single letter \"k\" (for \"kill\") will ask you for a process number to be killed. The second prompt will ask for the specific signal to send. The default offered is \"15/sigterm\", try this first (by simple pressing <tt>Enter</tt>. If this is not sufficient do the same again and enter \"9\" which stands for \"sigkill\".\n\nHelp for <tt>top</tt>:\n* press question mark '''?''' ''while running'' <tt>top</tt>\n* read the man page (<tt>man top</tt>) for detailed description\n\n* If <tt>top</tt> top fails: kill ''everything''\n''Only if you are sure that you are the only user on this physical machine:'' simple turn it off. This is acceptable because the Operating System is not stored locally but the machine performs remote boot. No files on disk can be damaged by a forced power cycle.\n\n== Problems with X forwarding ==\ntbw\n\n== See also ==\n* [[Shell]] \n* [[Remote Access/Single Command]]\n* [[PuTTY]]\n* [[FAQ]]\n* [[Xming]]\n* [[MobaXterm]]\n\n== Links ==\n\n[[Kategorie:Remote]]"
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            "85": {
                "pageid": 85,
                "ns": 0,
                "title": "Remote Access/Single Command",
                "revisions": [
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                        "*": "== Combine two ssh commands ==\nIf you know the final destination you can combine two sequential ssh commands into one single command by simple put them together in one line. The only required \"trick\" is the <tt>-t</tt> parameter. Without this the second hop \"hangs\" around without a connected <tt>tty</tt>-Terminal - no output/input is possible even though the connection is established.\n \nVerbatim terminal copy-n-paste (just eliminated some text):\n '''~$ ssh -t gtest2@login.stud ssh -t c034.cip.loc '''\n #######\n #######  login.stud.informatik.uni-goettingen.de  \n   ...\n ## Bitte auf einem der c0xx PC 'weiterhangeln' um zu arbeiten.\n ##\n #######\n gtest2@login.stud's password: \n Welcome to Ubuntu 14.04.3 LTS (GNU/Linux 3.13.0-68-generic x86_64)\n \n  * Documentation:  https://help.ubuntu.com/\n Last login: Wed Nov 25 16:07:41 2015 from login.cip.loc\n gtest2@c034:~$ \n\nExactly the same is possible with [[PuTTY]] - you just have to enter \"<tt>ssh cip034.cip.loc</tt>\" in the configuration setting ''Connection --> SSH --> Remote command:''. Works like a charm  ;-)\n\n=== GUI applications ===\nFor Linux this will also forward \"[[X]]\" - every installed graphical software will run on <tt>c034</tt> (in this example) and the graphical representation is displayed on the local machine.\n\nTo accomplish this on Windows you need an installed and running X-Server (e.g. [[Xming]]) of course.\n\n=== ProxyCommand ===\nAsking the All Knowing Trash Heap [https://en.wikipedia.org/wiki/List_of_Fraggle_Rock_characters#Marjory_the_Trash_Heap] you will find valid solutions using <tt>ProxyCommand</tt>. Putting this:\n\n Host C34\n   HostName c034.cip.loc\n   User myuserid\n   ProxyCommand ssh myuserid@login.stud.informatik.uni-goettingen.de nc %h %p \n\n...into your local <tt>.ssh/config</tt> does actually work - but in a way you will not like very much as you need to enter your password twice:\n* <tt>ssh C34</tt> does connect to <tt>login.stud</tt> - and you need to enter your password the first time to establish the connection\n* <tt>ProxyCommand</tt> has then been executed and the actual connection to <tt>c034</tt> is going to get established originating from your local computer. You need to satisfy the (second) password prompt coming from <tt>c034</tt> by entering the password a second time\n\nThe simpler double ssh approach from above uses [[Kerberos]] Ticket Forwarding. For this reason you only need to enter the password once. If you ''already'' have a valid Kerberos ticket you do not need to enter any password at all!  :-)\n\n(There are also some other positive effects though: using <tt>ProxyCommand</tt> simplifies solving some \"double-hop-port-forwarding\" issues.)\n\n== See also ==\n* [[Remote Access]]\n* [[PuTTY]]\n* [[FAQ]]\n* [[Xming]]\n\n== Links ==\n\n[[Kategorie:Remote]]"
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