RHCSA EX200 - Accessing linux systems LAB
- Log in and switch users in multiuser targets
- Access remote systems using SSH
- Configure Key-based authentication for SSH
- Securely transfer files between systems
csr@MainPC:~/Downloads$ ssh [email protected]
The authenticity of host '3.80.189.75 (3.80.189.75)' can't be established.
ED25519 key fingerprint is SHA256:4nFxuEkL7XMM8ehB0hYTUHPRJTYV0O8iyC8MsidjbUs.
This key is not known by any other names.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '3.80.189.75' (ED25519) to the list of known hosts.
([email protected]) Password:
Register this system with Red Hat Insights: insights-client --register
Create an account or view all your systems at https://red.ht/insights-dashboard
cloud_user@server1: ~ $ whoami ; groups
cloud_user
cloud_user wheel sysadmins
cloud_user@server1: ~ $ id
uid=1001(cloud_user) gid=1001(cloud_user) groups=1001(cloud_user),10(wheel),49999(sysadmins) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
cloud_user@server1: ~ $
This will show what happens and what files are sourced or executed when using different types of privilege elevations
cloud_user@server1: ~ $ sudo -i
[sudo] password for cloud_user:
root@server1: ~ # echo export SOURCED1=.bash_profile >> ~/.bash_profile ; echo 'echo $SOURCED1' >> ~/.bash_profile
root@server1: ~ # grep SOURCED .bash_profile
export SOURCED1=.bash_profile
echo $SOURCED1
root@server1: ~ # echo export SOURCED2=.bashrc >> ~/.bashrc ; echo 'echo $SOURCED2' >> ~/.bashrc
root@server1: ~ # grep SOURCED .bashrc
export SOURCED2=.bashrc
echo $SOURCED2
cloud_user@server1: ~ $ sudo -k ## When used without a command, invalidates the user's cached credentials for the current session. The next time sudo is run in the session, a password must be entered if the security policy requires authentication
cloud_user@server1: ~ $ sudo -i echo
[sudo] password for cloud_user:
.bashrc
.bash_profile
cloud_user@server1: ~ $ sudo -i passwd root
[sudo] password for cloud_user:
.bashrc
.bash_profile
Changing password for user root.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.
cloud_user@server1: ~ $ su -c 'echo $PATH'
Password:
/home/cloud_user/.local/bin:/home/cloud_user/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin
cloud_user@server1: ~ $ su - -c 'echo $PATH'
Password:
.bashrc
.bash_profile
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin
cloud_user@server1: ~ $
sudo = cloud_user
sudo -i = root user
su = cloud_user
su - = root user
Task 2 - access remote systems using ssh
Ssh to second server
cloud_user@server1: ~ $ ssh [email protected]
The authenticity of host '10.0.1.197 (10.0.1.197)' can't be established.
ECDSA key fingerprint is SHA256:FplhCnLMLm5YPqa00ssQlH/FEVGrxMaNkThmr4r8AaI.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '10.0.1.197' (ECDSA) to the list of known hosts.
Password:
Register this system with Red Hat Insights: insights-client --register
Create an account or view all your systems at https://red.ht/insights-dashboard
cloud_user@server2: ~ $
Retrieving information from remote server and creating a file to input data
cloud_user@server1: ~ $ ssh -t [email protected] df -hT >> server_health.txt
Password:
Connection to 10.0.1.197 closed.
cloud_user@server1: ~ $ ls
audit build init_pass mariadb_repo_setup Public server_health.txt Templates wget-1.19.5-8.el8_1.1.x86_64.rpm
cloud_user@server1: ~ $ cat server_health.txt
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 1.8G 0 1.8G 0% /dev
tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs tmpfs 1.9G 17M 1.9G 1% /run
tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/xvda2 xfs 20G 14G 6.7G 67% /
tmpfs tmpfs 373M 0 373M 0% /run/user/1001
cloud_user@server1: ~ $ ssh -t [email protected] df free >> server_health.txt
Password:
Connection to 10.0.1.197 closed.
cloud_user@server1: ~ $ cat server_health.txt
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 1.8G 0 1.8G 0% /dev
tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs tmpfs 1.9G 17M 1.9G 1% /run
tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/xvda2 xfs 20G 14G 6.7G 67% /
tmpfs tmpfs 373M 0 373M 0% /run/user/1001
df: free: No such file or directory
cloud_user@server1: ~ $ free
total used free shared buff/cache available
Mem: 3818520 279104 2419652 18768 1119764 3297500
Swap: 8388604 0 8388604
cloud_user@server1: ~ $ ssh [email protected]
Password:
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: Wed Apr 10 18:37:25 2024 from 10.0.1.151
cloud_user@server2: ~ $ free
total used free shared buff/cache available
Mem: 3818520 241588 2697600 18764 879332 3336480
Swap: 8388604 0 8388604
cloud_user@server2: ~ $ exit
logout
Connection to 10.0.1.197 closed.
cloud_user@server1: ~ $ ssh -t [email protected] free >> server_health.txt
Password:
Connection to 10.0.1.197 closed.
cloud_user@server1: ~ $ cat server_health.txt
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 1.8G 0 1.8G 0% /dev
tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs tmpfs 1.9G 17M 1.9G 1% /run
tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/xvda2 xfs 20G 14G 6.7G 67% /
tmpfs tmpfs 373M 0 373M 0% /run/user/1001
df: free: No such file or directory
total used free shared buff/cache available
Mem: 3818520 239348 2699840 18692 879332 3338776
Swap: 8388604 0 8388604
Task 3 - creating a keygen to ssh to remote server
cloud_user@server1: ~ $ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/cloud_user/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/cloud_user/.ssh/id_rsa.
Your public key has been saved in /home/cloud_user/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:Ag8dXpCf+hWNs+ftc4ItGtOET3s3vd6UKPAWwJCdlbg cloud_user@server1
The key's randomart image is:
+---[RSA 3072]----+
| o++ +.. |
| o.+o+ . |
| o o. +.o |
| + oE=.. |
| o.S..=o |
| .. ==o.. o|
| . .o*+=.o+|
| . .o=.=o=|
| .. oo*.|
+----[SHA256]-----+
cloud_user@server1: ~ $ ssh-copy-id 10.0.1.197
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/cloud_user/.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
Password:
Number of key(s) added: 1
Now try logging into the machine, with: "ssh '10.0.1.197'"
and check to make sure that only the key(s) you wanted were added.
cloud_user@server1: ~ $ ssh [email protected]
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: Wed Apr 10 18:38:22 2024 from 10.0.1.151
cloud_user@server2: ~ $
eval used on a Unix or Linux system to execute the arguments as a shell command. The eval command is helpful when you want to execute a Unix or Linux command that has been saved in a variable
ssh-agent is a background program that handles passwords for SSH private keys. The ssh-add command prompts the user for a private key password and adds it to the list maintained by ssh-agent. Once you add a password to ssh-agent, you will not be prompted for it when using SSH or scp to connect to hosts with your public key.
cloud_user@server1: ~ $ eval $(ssh-agent -s)
Agent pid 3231
cloud_user@server1: ~ $ ssh-add
Identity added: /home/cloud_user/.ssh/id_rsa (cloud_user@server1)
cloud_user@server1: ~ $ ssh [email protected]
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: Wed Apr 10 18:41:49 2024 from 10.0.1.151
cloud_user@server2: ~ $
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