Linux – Tools to Profile Memory and CPU

rsync is a free tool you can use to securely make copies of files and folders from one computer to another via the network. Once the initial copy is complete, only differences are sent on each future use.

Using rsync by itself will give you a copy of your data but there will be no retention, ie. once a file is changed in the source, when rsync runs again, that file will be changed in the target as well.

In order to get daily/weekly/monthly/yearly retention, you can combine rsync with some simple scripts that copy the target with hard links (so very little extra space is used in the target) before the next rsync executes.

By mounting the target backup location's parent folder read only, general users can browse historic backups and retrieve files without the need for any special graphical or web interface.

Take a look at http://www.mikerubel.org/computers/rsync_snapshots/ for a detailed explanation on how this works.

There is a package called rsnapshot which should make setup easy. In Ubuntu type sudo apt-get install rsnapshot.

rsnapshot details can be found at http://rsnapshot.org/

.bash_profile and .bashrc are specific to bash, whereas .profile is read by many shells in the absence of their own shell-specific config files. (.profile was used by the original Bourne shell.) .bash_profile or .profile is read by login shells, along with .bashrc; subshells read only .bashrc. (Between job control and modern windowing systems, .bashrc by itself doesn't get used much. If you use screen or tmux, screens/windows usually run subshells instead of login shells.)

The idea behind this was that one-time setup was done by .profile (or shell-specific version thereof), and per-shell stuff by .bashrc. For example, you generally only want to load environment variables once per session instead of getting them whacked any time you launch a subshell within a session, whereas you always want your aliases (which aren't propagated automatically like environment variables are).

Other notable shell config files:

/etc/bash_profile (fallback /etc/profile) is read before the user's .profile for system-wide configuration, and likewise /etc/bashrc in subshells (no fallback for this one). Many systems including Ubuntu also use an /etc/profile.d directory containing shell scriptlets, which are . (source)-ed from /etc/profile; the fragments here are per-shell, with *.sh applying to all Bourne/POSIX compatible shells and other extensions applying to that particular shell.