Posted in 2011

The hunt for /etc/.pwd.lock

After upgrade Debian to kernel 3.0.0, I saw a hidden file called .pwd.lock in /etc which I didn’t noticed before. Checking other machines gave the same result as shown below, but both without a matching Debian-package or manpage.

As time match at least the installation date of the machine and exists on other machines it appears to be a valid file, but with what purpose? After reading the Linux Programmer’s Manual two functions called lckpwdf and ulckpwdf where candidates for using this file. Checking the source code at Sourceware confirmed that both lckpwdf and ulckpwdf are using the file. And reading the manpage about these functions also confirms its purpose, a lock file the commands like passwd.

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