tramp: Remote programs
4.15 How TRAMP finds and uses programs on the remote host
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TRAMP requires access to and rights to several commands on remote hosts:
‘ls’, ‘test’, ‘find’ and ‘cat’.
Besides there are other required programs for 
Inline methods
and External methods of connection.
To improve performance and accuracy of remote file access, TRAMP uses
‘perl’ (or ‘perl5’) and ‘grep’ when available.
-- User Option: tramp-remote-path
‘tramp-remote-path’ specifies which remote directory paths TRAMP
can search for Remote programs.
TRAMP uses standard defaults, such as ‘/bin’ and ‘/usr/bin’, which
are reasonable for most hosts. To accommodate differences in hosts
and paths, for example, ‘/bin:/usr/bin’ on Debian GNU/Linux or
‘/usr/xpg4/bin:/usr/ccs/bin:/usr/bin:/opt/SUNWspro/bin’ on Solaris,
TRAMP queries the remote host with ‘getconf PATH’ and updates the
symbol ‘tramp-default-remote-path’.
For instances where hosts keep obscure locations for paths for
security reasons, manually add such paths to local ‘.emacs’ as
shown below for TRAMP to use when connecting.
(add-to-list 'tramp-remote-path "/usr/local/perl/bin")
Another way to find the remote path is to use the path assigned to
the remote user by the remote host. TRAMP does not normally retain
this remote path after logging. However, ‘tramp-own-remote-path’
preserves the path value, which can be used to update
‘tramp-remote-path’.
(add-to-list 'tramp-remote-path 'tramp-own-remote-path)
When remote search paths are changed, local TRAMP caches must be
recomputed. To force TRAMP to recompute afresh, exit Emacs, remove the
persistent file (Connection caching), and restart Emacs.
Info Catalog
tramp: Predefined connection information
tramp: Configuration
tramp: Remote shell setup