Protecting /etc/passwd and /etc/shadow from concurrent access

Protecting /etc/passwd and /etc/shadow from concurrent access

By : Paul Parker
Date : October 22 2020, 11:12 PM
seems to work fine I think most applications use PAM these days, don't they? http://www.kernel.org/pub/linux/libs/pam/Linux-PAM-html/Linux-PAM_ADG.html. That said, you might look at the source for `pam_unix.so' to see how they do it. I looked in pam_unix_passwd.c and followed this:
code :

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Does the Android operating system have files like /etc/passwd, /etc/shadow, and /etc/group?

Does the Android operating system have files like /etc/passwd, /etc/shadow, and /etc/group?

By : user2784114
Date : March 29 2020, 07:55 AM
To fix the issue you can do This thread discusses how that is done: http://groups.google.com/group/android-ndk/browse_thread/thread/adddb27c1a5438e9
It contains a broken link to a git repository though, you can find a list of name and IDs in https://android.googlesource.com/platform/system/core.git/+/master/include/private/android_filesystem_config.h.
Use of /etc/passwd-, /etc/shadow-, /etc/group-

Use of /etc/passwd-, /etc/shadow-, /etc/group-

By : user3681432
Date : March 29 2020, 07:55 AM
To fix this issue These are backups of previous versions.
Manual pages show these files and states:
Edited shadow and passwd to clear root password but new password doesn't work

Edited shadow and passwd to clear root password but new password doesn't work

By : abdul18
Date : March 29 2020, 07:55 AM
Any of those help It is possible that "/etc" is mounted on a ramdisk (or as tmpfs), which allows you to change the password at runtime but the changes are not propagated to the actual passwd and shadow files. The "/etc" is remounted on bootup from a flash device causing the old settings to be used.
After logging in to the system execute mount and check where "/" or "/etc" is mounted, then check the type. A value of tmpfs will prove the statements above. Also check if "/etc" is a link to a folder in "/var". "/var" is usually on tmpfs.
Can not add new user in docker container with mounted /etc/passwd and /etc/shadow

Can not add new user in docker container with mounted /etc/passwd and /etc/shadow

By : Shaller Yu
Date : March 29 2020, 07:55 AM
it helps some times It's failing because passwd manipulates a temporary file, and then attempts to rename it to /etc/shadow. This fails because /etc/shadow is a mountpoint -- which cannot be replaced -- which results in this error (captured using strace):
code :
102   rename("/etc/nshadow", "/etc/shadow") = -1 EBUSY (Device or resource busy)
# cd /etc
# touch foo
# mv foo shadow
mv: cannot move 'foo' to 'shadow': Device or resource busy
$ docker run -it --rm -v $PWD/my_etc:/my_etc centos
[root@afbc739f588c /]# ln -sf /my_etc/my_passwd /etc/passwd
[root@afbc739f588c /]# ln -sf /my_etc/my_shadow /etc/shadow
[root@afbc739f588c /]# ls -l /etc/{shadow,passwd}
lrwxrwxrwx. 1 root root 17 Oct  8 17:48 /etc/passwd -> /my_etc/my_passwd
lrwxrwxrwx. 1 root root 17 Oct  8 17:48 /etc/shadow -> /my_etc/my_shadow
[root@afbc739f588c /]# passwd root
Changing password for user root.
New password: 
Retype new password: 
passwd: all authentication tokens updated successfully.
[root@afbc739f588c /]# 
How can I pull a line out of /etc/passwd if its corresponding shadow entry is 999999?

How can I pull a line out of /etc/passwd if its corresponding shadow entry is 999999?

By : tals
Date : October 24 2020, 11:12 AM
help you fix your problem I want to compare each user in the passwd file with his entry in the shadow file, and print out the whole line of the passwd file if the entry in the shadow file matches 999999. What is the easiest way in Perl to do this? Or I suppose I could awk the values out of one file and match in the other file? What is the best way of doing this?
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