8.a Create, delete, and modify local user accounts
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Important Files:

/etc/skell - Skeleton folder
/etc/passwd - Password file
/etc/group - Group file
/etc/default/useradd - Default variables for useradd
/etc/login.defs - The /etc/login.defs file defines the site-specific configuration for the shadow password suite. This file is required. Absence of this file will not prevent system operation, but will probably result in undesirable operation.

Note that the shadow file, no one has permission:

$ ll /etc/shadow
----------. 1 root root 887 Jan 29  2019 /etc/shadow

Commands:

id (1) - print real and effective user and group IDs
getent (1) - get entries from Name Service Switch libraries
useradd (8) - create a new user or update default new user information
usermod (8) - modify a user account
whoami (1) - print effective userid
logname (1) - print user's login name
lslogins (1) - display information about known users in the system

Commands
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id - Print real and effective user and group IDs
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$ id
uid=1000(victor) gid=1000(victor) groups=1000(victor),10(wheel) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

📝 NOTE: When running for your own user, the highlighted text is shown

getent - get entries from Name Service Switch libraries
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This can be used to show information on local and directory services.

Shows /etc/passwd entry for user 'victor'

# getent passwd victor
victor:x:1000:1000:victor:/home/victor:/bin/bash

Shows /etc/shadow entry for user 'user1'

# getent shadow user1
user1:$6$i5IgGA0XFP/f3Hv3$./zCBLGuL24fc8njwvsGJlsgrB.QJzf1srrHMUpDzxgYyqwlepHrKUhbu.k9iwOMxLsdRuu.oNiRItGZiKNZE.:18592:0:99999:7:::

Shows all users in the system

# getent passwd

Shows all groups in the system

# getent group

useradd - Create a new user or update default new user information
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Useful command options:

c - Comment
d - Set home directory
g - Set the GID
G - Secondary groups
k - Skeleton directory
p - The encrypted password, as returned by crypt
r - Create a system account
s - Default login shell
u - Set the UID

Add a user named 'user1' with uid '1001' and the existing 'users' group

# useradd -u 1001 -g 100 user1

# id user1
uid=1001(user1) gid=100(users) groups=100(users)

usermod - Modify a user account
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Useful command options:

c - Modify user's comment
d- change the user's home directory
G - chage the user's secondary group
L - Locks the account
U - Unlocks the account

📝 NOTE: Locking the account adds a '!' at the beginning of the hash in /etc/shadow

⬅️ Back

8.a Create, delete, and modify local user accounts...

Commands...

id - Print real and effective user and group IDs...

getent - get entries from Name Service Switch libraries...