Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
linux_ssh_access [2019/01/02 16:34]
ktm5j
linux_ssh_access [2020/09/01 18:02] (current)
pgh5a
Line 1: Line 1:
-====== Linux SSH Access ​======+==== Linux Server ​Access ====
  
-All Linux servers ​in CS run an SSH server on port 22.  Anyone with a CS account may log into these servers, from both inside and outside of the University.+All Linux servers run "​secure shell" - '​ssh'​.  Anyone with a CS account may log into these servers. ​
  
-===== Server Domain Names =====+On Grounds, you can simply '​ssh'​ to CS servers typically by using a Terminal application like HyperTerm (Windows) or Terminal (Mac). 
 + 
 +Off Grounds, you are not able to '​ssh'​ directly into CS servers. ​ However connections to ''​%%portal.cs.virginia.edu%%''​ are allowed from off Grounds. 
 + 
 +You must use your CS domain userid (identical to your UVA userid) and password to '​ssh'​ to portal. For example: 
 + 
 +''​%%ssh -l abc1de portal.cs.virginia.edu%%''​. Alternatively,​ ''​%%ssh abc1de@portal.cs.virginia.edu%%''​ 
 + 
 +Note that if you are opening a terminal application on your Mac or PC, your username on the Mac or PC may be different from your CS/UVA userid. So be sure to include your userid on the '​ssh'​ command line. 
 + 
 +If you'd like to use a graphical windowing interface to department servers, see: [[nx_lab|NX Linux Remote Desktop Cluster]] 
 + 
 +=== Access from off Grounds === 
 + 
 +**Use one of these options to access CS servers from outside of UVA.** 
 + 
 +=== Option 1: VPN access === 
 + 
 + 
 +If you are outside of the UVA network (off grounds) then you can first start a VPN session to UVA using the [[https://​virginia.service-now.com/​its?​id=itsweb_kb_article&​sys_id=f24e5cdfdb3acb804f32fb671d9619d0|UVA VPN]]. Once the VPN is established,​ you can '​ssh'​ to CS servers directly. 
 + 
 +=== Option 2: Access via portal.cs.virginia.edu === 
 + 
 +You can ssh directly into ''​%%portal.cs.virginia.edu%%''​ without having to use the UVA VPN.  Once you are logged into the ''​%%portal%%''​ cluster, you can then ssh to other CS servers. 
 + 
 +<​code>​ 
 +[abc1de@outside-uva ~]$ ssh -l abc1de portal.cs.virginia.edu 
 +abc1de@portal.cs.virginia.edu'​s password:  
 +Last login: Mon Jul 29 14:12:10 2019 
 +abc1de@portal04 ~ $ hostname 
 +portal04 ​                                              <​-- We are logged into portal cluster 
 +abc1de@portal04 ~ $ ssh gpusrv01 ​                        <​-- We can now access gpusrv01 
 +abc1de@gpusrv01'​s password: 
 +.... 
 +abc1de@gpusrv01 ~ $ 
 +</​code>​ 
 + 
 +=== Jumphost Option === 
 + 
 +The ssh client has an option ''​%%-J%%''​ to specify a host to use as a "​jumphost"​ that lets you access other servers directly, in one step.  This combines two steps (for example, ssh into portal.cs.virginia.edu and then ssh to gpusrv01) into one single command. ​ From the //man// page: 
 + 
 +<​code>​ 
 +     -J destination 
 +             ​Connect to the target host by first making a ssh connection to 
 +             the jump host described by destination and then establishing a 
 +             TCP forwarding to the ultimate destination from there. ​ Multiple 
 +             jump hops may be specified separated by comma characters. ​ This 
 +             is a shortcut to specify a ProxyJump configuration directive. 
 +             Note that configuration directives supplied on the command-line 
 +             ​generally apply to the destination host and not any specified 
 +             jump hosts. ​ Use ~/​.ssh/​config to specify configuration for jump 
 +             ​hosts. 
 +</​code>​ 
 + 
 +Here is how we use this option to "​jump"​ from portal.cs to another CS server. ​ Let's repeat the example of logging in to ''​%%gpusrv01%%''​ 
 + 
 +<​code>​ 
 +[abc1de@outside-uva ~]$ ssh -l abc1de gpusrv01 -J portal.cs.virginia.edu 
 +abc1de@portal04.cs.virginia.edu'​s password: ​                           <-- first asked to authenticate to portal 
 +abc1de@gpusrv01'​s password: ​                                             <-- immediately able to log into gpusrv01 
 +.... 
 +abc1de@gpusrv01 ~ $ 
 +</​code>​ 
 + 
 +=== Server Domain Names ===
  
 Computer Science hosts its own DNS server with authority over the ''​%%cs.virginia.edu%%''​ domain space. ​ Any server in CS will have a fully qualified domain name (fqdn) of ''​%%hostname.cs.virginia.edu%%''​. Computer Science hosts its own DNS server with authority over the ''​%%cs.virginia.edu%%''​ domain space. ​ Any server in CS will have a fully qualified domain name (fqdn) of ''​%%hostname.cs.virginia.edu%%''​.
  
-If you want to log into a server named ''​%%gpusrv04%%'',​ then the domain address should be ''​%%gpusrv04.cs.virginia.edu%%''​.+=== Short Names ===
  
-===== Login =====+If you are inside of the Computer Science network then use the hostname of a server instead of its fully qualified name.  For example, if you are logged into a CS server, you can ping another server by its hostname alone.
  
-==== From Linux/Mac OS ====+<​code>​ 
 +abc1de@portal01:​~$ ping portal03 
 +PING portal03.cs.virginia.edu (128.143.67.43) 56(84) bytes of data. 
 +64 bytes from portal03.cs.virginia.edu (128.143.67.43):​ icmp_seq=1 ttl=64 time=0.149 ms 
 +64 bytes from portal03.cs.virginia.edu (128.143.67.43):​ icmp_seq=2 ttl=64 time=0.123 ms 
 +</​code>​ 
 + 
 +This will not work from outside of the CS network unless you modify your DNS search path to contain ''​%%cs.virginia.edu%%''​. 
 + 
 +=== Login to other servers === 
 + 
 +=== From Linux/Mac OS ===
  
-To log into this server from another computer running Linux/​Unix/​MacOS,​ run the following from a shell:+To log into server from another computer running Linux/​Unix/​MacOS,​ run the following from a shell:
  
 <​code>​ <​code>​
-username@host ~ $ ssh username@gpusrv04.cs.virginia.edu +abc1de@host ~ $ ssh username@gpusrv04.cs.virginia.edu 
-username@gpusrv04'​s password: ​                             <- Enter Password+abc1de@gpusrv04'​s password: ​                             <- Enter Password
 ... ...
-[username@gpusrv04 ~]$+[abc1de@gpusrv04 ~]$
 </​code>​ </​code>​
  
 In Mac OS the Terminal app can be found in the Utilities folder under Applications. In Mac OS the Terminal app can be found in the Utilities folder under Applications.
  
-==== From Windows ​====+=== From Windows ===
  
 For information about SSH clients for Windows, see the article [[windows_ssh|SSH from Windows]] For information about SSH clients for Windows, see the article [[windows_ssh|SSH from Windows]]
  
-===== Login Restrictions (Info for Faculty) =====+=== Servers ​===
  
-Here in CS we want to give all of our users fair and equal access to whatever computing resources we have to offer.  ​For this reason we are discontinuing the practice of restricting login access to certain servers. ​ However, there are number ​of servers ​that still have access restrictions ​in place. ​ This article ​is to show users with ''​%%sudo%%''​ privileges how to edit ''​%%/​etc/​security/​time.conf%%''​ to allow user logins.+For a listing ​of generally available ​servers in CS, see the article ​[[compute_resources|General Purpose Nodes]]
  
-There are several configuration files located in ''​%%/​etc/​security%%''​ on Linux servers. ​ In this directory, we can use ''​%%time.conf%%''​ to restrict ssh login to a specific set of user accounts.+=== Login Restrictions (Info for Faculty) ===
  
-==== PAM Setup ====+We want to give all of our users fair and equal access to whatever computing resources we have to offer. We do not restrict login access to certain servers. ​ However, there are a number of servers that still have access restrictions in place. ​ This article is to show users with ''​%%sudo%%''​ privileges how to edit ''​%%/​etc/​security/​time.conf%%''​ to allow user logins.
  
-This section ​can be skipped over if your server has already been configured with login restrictions.+There are several configuration files located in ''​%%/​etc/​security%%''​ on Linux servers. ​ In this directory, we can use ''​%%time.conf%%''​ to restrict ssh login to a specific set of user accounts.
  
 By default, access rules in ''​%%time.conf%%''​ are not used unless a //PAM module// (pluggable authentication module) is configured to read them.  This is done by adding a line to the ''​%%sshd%%''​ //PAM// module file.  ​ By default, access rules in ''​%%time.conf%%''​ are not used unless a //PAM module// (pluggable authentication module) is configured to read them.  This is done by adding a line to the ''​%%sshd%%''​ //PAM// module file.  ​
Line 45: Line 120:
 account ​            ​required ​               pam_time.so account ​            ​required ​               pam_time.so
 </​code>​ </​code>​
- 
-==== time.conf ==== 
  
 Now that //PAM// is configured to read ''​%%time.conf%%''​ we can now put in a rule.  Here is an example rule from ''​%%time.conf%%'':​ Now that //PAM// is configured to read ''​%%time.conf%%''​ we can now put in a rule.  Here is an example rule from ''​%%time.conf%%'':​
  • linux_ssh_access.1546446844.txt.gz
  • Last modified: 2019/01/02 16:34
  • by ktm5j