B. Use Ssh Secure File Transfer to Upload the Page(S) Just Created to Uhunix

Let's start off by talking virtually jump/bastion hosts and why they're so handy. It's becoming more than and more common that the remote server y'all desire to access isn't directly And that's a practiced affair, because:

• awarding servers, most of the times, should non exist exposed directly to the net.
• if you are using IPv4, there is no need for a public IPv4 address for each of your servers.
• only a unmarried host's firewall needs to be configured to allow your role IP, which saves a lot of work when this IP changes.

Passing through a bound host can be annoying because you need to SSH through multiple servers. Luckily, at that place are multiple means to exercise this. I've listed four methods below!

How to pass through a jump host

1. 'Manually'

One method of passing through a jump host is to SSH into the jump host and and then from the jump host SSH into your server.

            user@local-reckoner $ ssh jumphostuser@my-leap-host jumphostuser@my-leap-host $ ssh remoteserveruser@my-remote-server [remoteserveruser@my-remote-server ~]$          

You'll soon come up to the conclusion that connecting to your remote server from the jump host requires an SSH key on the bound host. A solution could be to create an SSH fundamental on the leap host, but this isn't an option for jump hosts that are replaced on a regular footing. This probably isn't a suitable method for most of us, so let's go on to the adjacent method. Oh, and by the way: never re-create your local SSH key to another host such as a jump host!

2. Amanuensis forwarding

I have already explained the ssh-agent concept in the first web log post of this serial. With amanuensis forwarding, you can expose your local ssh-agent on a remote server, such as a jump host. You tin can either utilize the control line option-A or the config file pickForwardAgent.

            user@local-computer $ ssh-add together Enter passphrase for /Users/janbeerden/.ssh/id_rsa: Identity added: /Users/user/.ssh/id_rsa (/Users/user/.ssh/id_rsa)   user@local-computer $ ssh -A jumphostuser@my-jump-host jumphostuser@my-jump-host $ ssh remoteserveruser@my-remote-server [remoteserveruser@my-remote-server ~]$          

Past doing this, you no longer need an intermediary primal. Your business relationship on the spring host and the remote server should only contain the public part of your local SSH key. Easy enough, correct?

However, because you are exposing your local ssh-agent to the bound host, the jump host can use your SSH primal without needing the passphrase. If you are the only one using (and maintaining) this spring host, you're probably fine. If that isn't the case (probably most of the times), someone could use your fundamental while it'due south being forwarded to the jump host.

When starting an SSH connection with agent forwarding enabled, the SSH server will create a socket to expose your ssh-amanuensis. Simply your user on the leap host will take permissions on this socket, but these restrictions do not use to the root user or any user that has plenty permissions via sudo.

3. ProxyCommand

With the ProxyCommand selection, yous can specify a control to be used to connect to the remote server. This choice can be used to 'concatenation' SSH connections. By using "ssh -W" as ProxyCommand, nosotros asking that standard input and output on the client is forwarded to Hostname over the secure channel to my-jump-host.

            Host my-leap-host   Hostname 192.168.0.10   User jumphostuser   Host my-remote-server   Hostname 192.168.five.10   User remoteserveruser   ProxyCommand ssh my-bound-host -W %h:%p          

Every bit y'all tin can meet, this requires some configuration, merely that only needs to be done once.

            user@local-computer $ ssh my-remote-server [remoteserveruser@my-remote-server ~]$          

Once this configuration is in place, you tin ssh 'directly' in to your remote server. Passing through the bastion host is taken care of by the ProxyCommand.

four. ProxyJump (I recommend this one!)

Since OpenSSH 7.three, there is an easier to configure alternative to ProxyCommand called ProxyJump.

            Host my-jump-host   Hostname 192.168.0.10   User jumphostuser   Host my-remote-server   Hostname 192.168.5.10   User remoteserveruser   ProxyJump my-jump-host          

Equally yous can come across, this option'southward configuration is a lot simpler.

            user@local-figurer $ ssh my-remote-server [remoteserveruser@my-remote-server ~]$          

Connecting to your remote server is no different from the ProxyCommand method. If you lot want to connect to a remote server without having to add information technology to your config file via a jump host (that you have added to your config file), ProxyJump is as well very simple.

            user@local-figurer $ ssh remoteserveruser@192.168.0.twenty -J my-jump-host          

When you lot share an SSH config file with your team, y'all tin also include the config shown above. They will certainly appreciate not having to create or add the configuration themselves!

I recommend this method instead of the others considering:

• method 1 is too much effort each time you want to SSH to your remote server,
• method two is a security chance and still requires multiple steps each time you lot desire to SSH to your remote server,
• method 3's syntax is more circuitous and thus less easy to remember than the ProxyJump method.

With methods 3 and 4, y'all will also have the do good of being able to transfer files directly to your remote server using scp or sftp without having to re-create them to the jump host first. But how exactly do you offset transferring files and then? We'll dive into the details of file transfer, merely first let me tell you about using 'screen'.

Using 'screen'

Since each bound host introduces an actress point of failure, now is the perfect time to kickoff using 'screen'. Have you ever had your SSH session disconnect while running a lengthy and/or delicate process on a remote server? When your SSH session gets disconnected, all processes started in the session that are running on the foreground volition be terminated. This will require you to start all over or, depending on the process, leave you lot with a mess to make clean upwardly manually. Luckily, y'all can preclude this from becoming a problem by using 'screen'. From its human page:

Screen is a total-screen window managing director that multiplexes a concrete terminal between several processes (typically interactive shells).

Some benefits of using screen:

• your shell remains active when your SSH session gets asunder,
• you can run lengthy processes on a remote server without the need of maintaining an agile SSH connectedness,
• you can use multiple windows from a unmarried SSH session.

Start of all, screen needs to exist installed on your remote server. If screen isn't installed nonetheless, you lot tin use your systems package manager to install information technology.

Starting a new screen

Starting a screen is very elementary:

            [remoteserveruser@my-remote-server ~]$ screen          

Screen will create a new shell, similarly as SSH'ing into a server would.

Disconnecting from a screen

The difference from a 'standard' beat out is that you can disconnect from it, without killing all the sub processes. First y'all need to enter the escape command, which isCTRL+a, followed pastCTRL+d

            [detached from 4389.pts-0.my-remote-server] [remoteserveruser@my-remote-server ~]$          

Screen will tell yous it detached you from a screen session. In this case, the session is chosen 4389.pts-0.my-remote-server. If you want to exit the shell instead of disconnecting for the screen session, you lot can practice so as if information technology is whatsoever other shell. Enter:

• go out
• CTRL + d
• ...

All the same, be careful! Screen does not protect you from accidentally exiting your shell.

Listing active screen sessions

With the-ls selection, you tin list all active screen sessions.

            [remoteserveruser@my-remote-server ~]$ screen -ls There are screens on:     4405.pts-0.my-remote-server (Detached)     4389.pts-0.my-remote-server (Discrete) 2 Sockets in /var/run/screen/Due south-remoteserveruser.          

Each line consists of the process id and the session proper name, separated by a period.

Starting a new screen with a custom session name

As you can run into from the output higher up, screen sessions can exist hard to identify. Therefore, information technology might be wise to name your screen session when starting it:

            [remoteserveruser@my-remote-server ~]$ screen -South server-upgrade [remoteserveruser@my-remote-server ~]$ screen -ls There are screens on:         4475.server-upgrade     (Fastened) one Socket in /var/run/screen/South-remoteserveruser.          

Attaching to a detached screen session

When you want to re-attach to a screen session, yous can practice then with the -r  option. This choice takes either the procedure id or the session name as parameter.

            [remoteserveruser@my-remote-server ~]$ screen -r server-upgrade          

Multiple windows in a unmarried screen session

Each of the post-obit subsections assume yous are fastened to a screen session.

Creating a new window inside your screen session

By issuingCTRL+a followed byCTRL+c, you create a new window.

List of open windows

By issuingCTRL+a followed byCTRL+w, y'all get a list of open up windows.

            [remoteserveruser@my-remote-server ~]$     0$ bash  1-$ fustigate  2*$ bash          

As you can see from the output above, I have 3 open windows, identified by a number followed by its title.

Switching betwixt windows

There are 4 (5) ways to switch between windows:

1. switch to a specific window
   1. CTRL+a followed by the number of the window
   2. CTRL+a followed by", this method is probably the easiest since it presents you with an interactive window selector. By using the arrow keys, you tin select the desired screen and press the return key to select it.
2. switch to the side by side window:CTRL+a followed byn
3. switch to the previous window:CTRL+a followed pastp
4. switch to the last window:CTRL+a followed byo

Other screen key bindings

There are several keys bindings that can be used inside a screen session, afterward issuing the control command (CTRL+a). You can get an overview of the available key bindings by pressing the? key. HittingCTRL+a showtime, and then hitting the? central.

                          Screen key bindings, page 1 of two.                        Command primal:  ^A   Literal ^A:  a   break       ^B b         license     ,            removebuf   = articulate       C            lockscreen  ^X x         reset       Z colon       :            log         H            screen      ^C c copy        ^[ [         login       Fifty            select      ' detach      ^D d         meta        a            silence     _ digraph     ^V           monitor     M            split       Due south displays    *            side by side        ^@ ^N sp n   suspend     ^Z z dumptermcap .            number      N            fourth dimension        ^T t fit         F            only        Q            title       A catamenia        ^F f         other       ^A           vbell       ^M focus       ^I           pow_break   B            version     v hardcopy    h            pow_detach  D            width       W help        ?            prev        ^H ^P p ^?   windows     ^West w history     { }          quit        \            wrap        ^R r info        i            readbuf     <            writebuf    > kill        K k          redisplay   ^L l         xoff        ^Southward s lastmsg     ^One thousand m         remove      X            xon         ^Q q                     [Press Infinite for adjacent page; Render to end.]          

I of my favorites is copy . Every bit the proper name gives away, information technology tin be used to copy text from one window to some other. For a complete overview and explanation of the available control line options and primal bindings, please have a look at the man

            user@local-reckoner $ scp my-remote-server:~/file.txt ~/Downloads/local/          

To

            user@local-computer $ scp ~/Downloads/local/file.txt my-remote-server:~/          

Between

            user@local-calculator $ scp my-remote-server:~/file.txt my-other-remote-server:~/          

For more information nearly using scp, accept a look at it's homo folio.

            user@local-computer $ man scp          

sftp or secure file transfer protocol is an interactive file transfer programme similar to ftp which allows you to securely copy files to or from a remote server. By entering the "?" control you lot will become a list of possible commands.

            user@local-computer $ sftp my-remote-server sftp> ? Available commands: bye                                Quit sftp cd path                            Alter remote directory to 'path' chgrp grp path                     Change group of file 'path' to 'grp' chmod manner path                    Change permissions of file 'path' to 'mode' chown own path                     Alter owner of file 'path' to 'own' df [-how-do-you-do] [path]                    Display statistics for current directory or                                    filesystem containing 'path' get out                               Quit sftp become [-afPpRr] remote [local]       Download file reget [-fPpRr] remote [local]      Resume download file reput [-fPpRr] [local] remote      Resume upload file help                               Display this help text lcd path                           Modify local directory to 'path' lls [ls-options [path]]            Display local directory listing lmkdir path                        Create local directory ln [-s] oldpath newpath            Link remote file (-s for symlink) lpwd                               Print local working directory ls [-1afhlnrSt] [path]             Display remote directory list lumask umask                       Fix local umask to 'umask' mkdir path                         Create remote directory progress                           Toggle brandish of progress meter put [-afPpRr] local [remote]       Upload file pwd                                Display remote working directory quit                               Quit sftp rename oldpath newpath             Rename remote file rm path                            Delete remote file rmdir path                         Remove remote directory symlink oldpath newpath            Symlink remote file version                            Prove SFTP version !command                           Execute 'command' in local shell !                                  Escape to local beat out ?                                  Synonym for assist          

For more than data nigh using sftp, have a look at it's man folio.

            user@local-computer $ man sftp          

            user@local-reckoner $ ssh remoteserveruser@my-remote-server "tar -zcf - /var/log/" > ~/log-archive.tgz          

To

            user@local-calculator $ tar -zcf - /var/log/ | ssh remoteserveruser@my-remote-server "cat - > ~/log-archive.tgz"          

Between

            user@local-reckoner $ ssh remoteserveruser@my-remote-server "tar -zcf - /var/log/" | ssh remoteserveruser@my-remote-server "cat - > ~/log-archive.tgz"          

In the examples above y'all volition notice I apply a dash "-" as the file name, this is the way of instructing tar, true cat and several other programs to write to standard output (stdout) or read from standard input (stdin).
And there nosotros have it! As always, if you lot have any questions or remarks, permit us know.

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Source: https://www.acagroup.be/en/blog/jump-hosts-file-transferring/

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