Solution to error reporting when root changes password under Linux

When I was preparing to change the root user password of the Linux system today, I executed passwd root. The following situation occurred and the password change failed:

# passwd root
Changing password for user root.
New password:
Retype new password:
passwd: Authentication token manipulation error

After searching on the Internet, some said it was caused by running out of inodes, that is, the root partition was full, but executing df -i did not find the reason:

# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/sda2 6406144 58534 6347610 1% /
tmpfs 8242797 2 8242795 1% /dev/shm

Continue to look for answers and check the system files /etc/passwd and /etc/shadow related to user passwords according to online cases. It is found that the permissions of these two files have the i option. The query results are as follows:

# lsattr /etc/passwd
—-i——–e- /etc/passwd
# lsattr /etc/shadow
—-i——–e- /etc/shadow

Note: In the Linux system, if the file has the i option, it means that no modifications can be made to it, which also leads to the failure to change the password.

To solve this problem, you need to execute the chattr -i command to revoke the i permissions of the above two files

# chattr -i /etc/passwd
# chattr -i /etc/shadow
# lsattr /etc/passwd
————-e- /etc/passwd
# lsattr /etc/shadow
————-e- /etc/shadow

Then execute passwd to change the password,

# passwd
Changing password for user root.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.

After changing the password, for security reasons, you can execute chattr i to add i permissions to the user password system file

# chattr +i /etc/passwd
# chattr +i /etc/shadow
# lsattr /etc/passwd
—-i——–e- /etc/passwd
# lsattr /etc/shadow
—-i——–e- /etc/shadow

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