System Access and File Transfer

Lab: Access RHEL System from Another RHEL System

issue the ssh command as user1 on server10 to log in to server20.
Run appropriate commands on server20 for validation.
Log off and return to the originating system.

1. Issue the ssh command as user1 on server10:

[user1@server30 tmp]$ ssh server20

2. Issue the basic Linux commands whoami, hostname, and pwd to confirm that you are logged in as user1 on server20 and placed in the correct home directory:

[user1@server40 ~]$ whoami
user1
[user1@server40 ~]$ hostname
server40
[user1@server40 ~]$ pwd
/home/user1

3. Run the logout or the exit command or simply press the key combination Ctrl+d to log off server20 and return to server10:

[user1@server40 ~]$ exit
logout
Connection to server40 closed.

If you wish to log on as a different user such as user2 (assuming user2 exists on the target server server20), you may run the ssh command in either of the following ways:

[user1@server30 tmp]$ ssh -l user2 server40

[user1@server30 tmp]$ ssh user2@server40

Lab: Generate, Distribute, and Use SSH Keys

Generate a passwordless ssh key pair using RSA algorithm for user1 on server10.
display the private and public file contents.
Distribute the public key to server20 and attempt to log on to server20 from server10.
Show the log file message for the login attempt.

1. Log on to server10 as user1.

2. Generate RSA keys without a password (-N) and without detailed output (-q). Press Enter when prompted to provide the filename to store the private key.

[user1@server30 tmp]$ ssh-keygen -N "" -q
Enter file in which to save the key (/home/user1/.ssh/id_rsa):

View the private key: [user1@server30 tmp]$ cat ~/.ssh/id_rsa

View the public key: [user1@server30 tmp]$ cat ~/.ssh/id_rsa.pub

3. Copy the public key file to server20 under /home/user1/.ssh directory.

user1@server30 tmp]$ ssh-copy-id server40
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/user1/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
user1@server40's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'server40'"
and check to make sure that only the key(s) you wanted were added.

This command also creates or updates the known_hosts file on server10 and stores the fingerprints for server20 in it.

[user1@server30 tmp]$ cat ~/.ssh/known_hosts

4. On server10, run the ssh command as user1 to connect to server20. You will not be prompted for a password because there was none assigned to the ssh keys.

[user1@server30 tmp]$ ssh server40
Register this system with Red Hat Insights: insights-client --register
Create an account or view all your systems at https://red.ht/insights-dashboard
Last login: Sun Jul 21 01:20:17 2024 from 192.168.0.30

View this login attempt in the /var/log/secure file on server20: [user1@server40 ~]$ sudo tail /var/log/secure

Executing Commands Remotely Using ssh

Can use ssh command to run programs without remoting in:

Execute the hostname command on server20:

[user1@server30 tmp]$ ssh server40 hostname
server40

Run the nmcli command on server20 to show (s) active network connections(c):

[user1@server30 tmp]$ ssh server40 nmcli c s
NAME    UUID                                  TYPE      DEVICE 
enp0s3  1c391bb6-20a3-4eb4-b717-1e458877dbe4  ethernet  enp0s3 
lo      175f8a4c-1907-4006-b838-eb43438d847b  loopback  lo

sftp` command

Interactive file transfer tool.

On server10, to connect to server20:

[user1@server30 tmp]$ sftp server40
Connected to server40.
sftp>

Type ? at the prompt to list available commands along with a short description:

[user1@server30 tmp]$ sftp server40
Connected to server40.
sftp> ?
Available commands:
bye                                Quit sftp
cd path                            Change remote directory to 'path'
chgrp [-h] grp path                Change group of file 'path' to 'grp'
chmod [-h] mode path               Change permissions of file 'path' to 'mode'
chown [-h] own path                Change owner of file 'path' to 'own'
df [-hi] [path]                    Display statistics for current directory or
                                   filesystem containing 'path'
exit                               Quit sftp
get [-afpR] remote [local]         Download file
help                               Display this help text
lcd path                           Change 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 listing
lumask umask                       Set local umask to 'umask'
mkdir path                         Create remote directory
progress                           Toggle display of progress meter
put [-afpR] local [remote]         Upload file
pwd                                Display remote working directory
quit                               Quit sftp
reget [-fpR] remote [local]        Resume download file
rename oldpath newpath             Rename remote file
reput [-fpR] local [remote]        Resume upload file
rm path                            Delete remote file
rmdir path                         Remove remote directory
symlink oldpath newpath            Symlink remote file
version                            Show SFTP version
!command                           Execute 'command' in local shell
!                                  Escape to local shell
?                                  Synonym for help

Example:

sftp> ls
sftp> mkdir /tmp/dir10-20
sftp> cd /tmp/dir10-20
sftp> pwd
Remote working directory: /tmp/dir10-20
sftp> put /etc/group
Uploading /etc/group to /tmp/dir10-20/group
group                                       100% 1118     1.0MB/s   00:00    
sftp> ls -l
-rw-r--r--    1 user1    user1        1118 Jul 21 01:41 group
sftp> cd ..
sftp> pwd
Remote working directory: /tmp
sftp> cd /home/user1
sftp> get /usr/bin/gzip
Fetching /usr/bin/gzip to gzip
gzip                                        100%   90KB  23.0MB/s   00:00    
sftp>

lcd, lls, lpwd, and lmkdir are run on the source server.
Other commands are also available. (See man pages)

Type quit at the sftp> prompt to exit the program when you’re done:

sftp> quit
[user1@server30 tmp]$