Add user manually (BusyBox / OpenWrt)

This guide explains how to manually create a local user on minimal systems such as OpenWrt or BusyBox environments where adduser and useradd are not available.

This method avoids manual /etc/shadow editing errors by using chpasswd.

The process requires editing:

• /etc/passwd
• /etc/group
• Setting password via chpasswd

1. Determine Next Available UID

Automatically calculate the next free UID to avoid collisions.

UID=$(($(awk -F: '{print $3}' /etc/passwd | sort -n | tail -1)+1))
echo "Next UID: $UID"

1. Verify Bash Exists (If Using Bash)

Before assigning /bin/bash, confirm it exists.

ls -l /bin/bash

If it does not exist, use /bin/ash instead.

1. Create Group

echo "wuseman:x:$UID:" >> /etc/group

• Format:

  groupname:x:GID:
  

• Add User to /etc/passwd

echo "wuseman:x:$UID:$UID:wuseman:/home/wuseman:/bin/bash" >> /etc/passwd

• Format:

username:x:UID:GID:comment:home:shell

1. Create Home Directory

mkdir -p /home/wuseman
chown $UID:$UID /home/wuseman
chmod 700 /home/wuseman

1. Set Password (Safe & Correct Method)

echo 'wuseman:password' | chpasswd

This:

• Automatically generates the correct password hash
• Sets proper last password change date
• Updates /etc/shadow safely
• Avoids * Formatting mistakes
• Prevents “wrong password” issues

• Requires no manual shadow editing

• Verify User

grep wuseman /etc/passwd
grep wuseman /etc/shadow
ls -ld /home/wuseman

Notes

• Ensure /bin/bash exists before assigning it as shell.
• Always test login in a second SSH session before closing root.
• Avoid hardcoding UID values.
• Prefer chpasswd over manual /etc/shadow editing.
• Consider SSH key authentication instead of passwords on production devices.

Security Reminder

• Editing authentication files incorrectly can lock you out of the device.
• Always verify access in a second session before logging out.