translucency is a loadable kernel module for Linux that virtually merges two directories, making it possible to overwrite files on read-only media and compile projects (such as the Linux kernel) with different options without copying sources each time. No user-space tools have to be changed. The process is also known as inheriting (ifs), stacking, translucency (tfs), loopback (lofs), and overlay (ovlfs).
ttmap passively analyzes values of TCP Timestamps in captured IP packets. After collecting enough data, it computes characteristic remote machine parameters. These values let it guess remote operating systems and identify unique machines behind a single IP address. For example, it can analyze remote IP load-balanced clusters.
v9fs provides a Plan 9 9P2000 resource sharing protocol for the Linux 2.6 kernel. This can be used to share files, devices, /proc, /sys, etc. It also works with Plan 9 file servers, and can be used to mount synthetic file systems from Plan 9 applications (see the plan9port project).
vpopmail (vchkpw) is a collection of programs and a library to automate the creation and maintenance of virtual domain email configurations for qmail installations using either a single UID/GID or any valid UID/GID in /etc/passwd with a home directory. Features are provided in the library for other applications which need to maintain virtual domain email accounts. It supports named or IP-based domains. It works with vqadmin, qmailadmin, vqregister, sqwebmail, and courier-imap. It supports MySQL, Sybase, Oracle, LDAP, and file-based (DJB constant database) authentication. It supports SMTP authentication combined with the qmail-smtp-auth patch. It supports user quotas and roaming users (SMTP relay after POP authentication).
vzhaipd (scoyo's Virtuozzo/OpenVZ HA IP Daemon) is a set of mount/umount Container scripts for Parallels Virtuozzo or OpenVZ that will make sure a HA IP is always present on one of two or more Containers. You can think of it as the poor man's VRRP for Virtuozzo and OpenVZ Containers. Use it for general service availability, software load-balancer failover, etc.
weta-dfs is a distributed file system. It is designed to be fail-safe through replications of files, fast and easy to install, platform independent, and to have fast recovery from crashes. It consists of Data Node Servers and one Meta Data Server and a java.io.File-like client API.