GetEnt : Linux Commands

getent command in Linux with examples

getent is a Linux command that helps the user to get the entries in a number of important text files called databases

https://www.geeksforgeeks.org/getent-command-in-linux-with-examples/

AWS : EC2 :Full Troubleshooting List

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/TroubleshootingInstancesConnecting.html#TroubleshootingInstancesServerError

Connection problems and errors

• Common causes for connection issues
• Error connecting to your instance: Connection timed out
• Error: unable to load key ... Expecting: ANY PRIVATE KEY
• Error: User key not recognized by server
• Error: Permission denied or connection closed by [instance] port 22
• Error: Unprotected private key file
• Error: Private key must begin with "-----BEGIN RSA PRIVATE KEY-----" and end with "-----END RSA PRIVATE KEY-----"
• Error: Server refused our key or No supported authentication methods available
• Cannot ping instance
• Error: Server unexpectedly closed network connection
• Error: Host key validation failed for EC2 Instance Connect

AWS : EC2: EBS : Mounting /Attaching EBS Volume : Duplicate UUID : Issue

sudo   mount -o   nouuid    /dev/xvdf2    /mnt/temp
 

https://stackoverflow.com/questions/55833917/unable-to-mount-a-volume-on-an-ec2-instance/55845557#55845557

https://stackoverflow.com/questions/55833917/unable-to-mount-a-volume-on-an-ec2-instance

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/TroubleshootingInstancesConnecting.html#TroubleshootingInstancesServerError

Linux "Stat" Comand | OCTAL Permission

 stat - -format="%a" /path1/subdir

https://www.cyberciti.biz/faq/get-octal-file-permissions-from-command-line-on-linuxunix/

https://unix.stackexchange.com/questions/188674/how-to-get-file-permission-in-octal

To just see octal file permissions on a GNU/Linux:
$ stat -c '%a' /etc/passwd

linux "Id" Command

https://www.geeksforgeeks.org/id-command-in-linux-with-examples/

Linux: List of all Users and All Groups

https://linuxize.com/post/how-to-list-users-in-linux/

• less /etc/passwd

• getent passwd
• getent passwd | cut -d: -f1

https://linuxize.com/post/how-to-list-groups-in-linux/

• less /etc/group

• getent group
• getent group | cut -d: -f1

Linux : /etc/passwd vs /usr/bin/passwd (passwd Utility) vs /etc/shadow vs /etc/group

https://stackoverflow.com/questions/50904342/etc-passwd-vs-usr-bin-passwd

The two files are different, and serve different purpose.

• /etc/passwd is user database (fun fact: contrary to its name, it doesn't store passwords - those are stored (possibly in hashed form) in /etc/shadow) - see man 5 passwd (i.e. passwd(5)), man 5 shadow (i.e. shadow(5)).

• /usr/bin/passwd is utility that is supposed to modify user records stored in /etc/passwd and /etc/shadow. See man 1 passwd (i.e. passwd(1))