On 12Feb2020 19:09, Roger Heflin <rogerhef...@gmail.com> wrote:
It may be the pwd command doing it.  It works like this:

if something runs pwd when its cwd is under say /var/log then pwd goes
through all files in /var/log until it finds .. then it goes up a
directory and repeats, until it gets to /.

getcwd() is a system call on Linux since 2.1.92. It doesn't need to perform the expensive ".. then stat everything for a match" loop.

[... snip arranging mounts to be in more out-of-the-way places ...]

On Wed, Feb 12, 2020 at 1:11 PM Dave Ulrick <d-ulr...@comcast.net> wrote:
I ran 'strace' on 'ls' but nothing interesting showed up. Then, I ran
'strace' on 'bash'. I ran 'ls' from 'bash' and then exited. The strace
log shows two connect()s to a socket file under /var/run:

connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) =
T (No such file or directory)

/var/run/nscd/socket appears to be related to the 'nscd' DNS cache which
I am not running on my PCs.


So, it looks likely that reading /var/run caused the contents of /var to
be read. This would have triggered a wakeup of the device hosting
/var/backups which would be a cause of its hard drive spinning up.

This would surprise me; accessing a direct name doesn't require stating everything adjacent.

You can test this:

- wait for the drive to spin down
- type ">>var/run/nscd/socket" and preess <enter> (do NOT filecomplete that path, your shell will do unwanted filesystem access)
- see if/when the drive spins up

Cameron Simpson <c...@cskk.id.au>
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