16 02 | 2012

OpenSSH tip: connection sharing

Written by Tanguy

Classified in : Homepage, Debian, Command line, To remember

The last versions of OpenSSH brought an interesting feature: sharing multiple sessions over a single connection. When enabled, this is how it works:

  1. The first time you open an SSH connection to a server (including anything that works on top of SSH, like SCP, SFTP, rsync or Git), it opens a network connection as usual. It also opens a local Unix socket and listens to it for later use.
  2. The next times you open an SSH connection to that server while the first one is still open, instead of opening a new network connection, it connects to that local Unix socket and lets the first SSH client carry its new session.

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20 05 | 2011

cpio > tar

Written by Tanguy

Classified in : Homepage, Debian, Miscellaneous

Large package icon

tar and cpio

tar(5) and cpio(5) are two competing archive formats, that provide almost identical features. Both are streamed formats, originally designed to be used on tapes. Their major practical difference is the style of their standard command line utilities:

  • cpio(1) takes the list of files to archive on its standard input, allowing a very high control but requiring to use another utility such as find(1) to archive an entire tree;
  • tar(1) usually takes the list of file to archive on its command line, and browses directories recursively be default.

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