Y2038 safe version of lastlog

lastlog reports the last login of a given user or of all users who did ever login on a system.

The standard /var/log/lastlog implementation using lastlog.h from glibc uses a 32bit time_t in struct lastlog on bi-arch systems like x86-64 (so which can execute 64bit and 32bit binaries). So even if you have a pure 64bit system, on many architectures using glibc you have a Y2038 problem.

For background on the Y2038 problem (32bit time_t counter will overflow) I suggest to start with the wikipedia Year 2038 problem article.

There is also a more technical document, describing the problem in more detail, which also contains a list of affected packages. And a more highlevel blog "Y2038, glibc and /var/log/lastlog on 64bit architectures"

Additional, /var/log/lastlog can become really huge if there are big UIDs in use on the system. Since it is a sparse file, this is normally not a problem, but depending on the filesystem or the tools used for backup, this can become a real problem.

Since there are only few applications which really support lastlog, the data is also not always correct.

lastlog2 tries to solve these problems:

• It's using sqlite3 as database backend.
• Data is only collected via a PAM module, so that all tools can make use of it, without modifying existing packages.
• The output is as compatible as possible with the old lastlog implementation.
• The old /var/log/lastlog file can be imported into the new database.
• The size of the database depends on the amount of users, not how big the biggest UID is.

IMPORTANT To be Y2038 safe on 32bit architectures, the binaries need to be built with a 64bit time_t. This should be the standard on 64bit architectures.

Besides the lastlog2 library in this directory there are additional parts like service definition, PAM module and applications:

• liblastlog2.so.0 contains all high level functions to manage the data (util-linux/liblastlog2).
• pam_lastlog2.so shows the last login of a user and stores the new login into the database (util-linux/pam_lastlog2).
• lastlog2 will display the last logins for all users, who did ever login (util-linux/misc-utils).
• lastlog2-import.service a service which imports lastlog data into lastlog2 database (util-linux/misc-utils).
• lastlog2.conf configuration for tmpfiles.d. See tmpfiles.d(5) for details (util-linux/misc-utils).

By default the database will be written as /var/lib/lastlog/lastlog2.db.