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Re: Debian glossary?




Richard Owlett <rowlett@xxxxxxxxxxx> writes:

> Debian documentation NOT written for hoi polloi.
>
> This morning's partial set of items I do not grok include:
> <problems described in {...}>
>
> Partial output of "mount -l" is
> "/dev/sdc1 on /media/richard/rco1 type ext4
> (rw,nosuid,nodev,relatime,data=ordered,uhelper=udisks2) [rco1]".
>
> { (...) Although I can interpret many items, several I can't. I
> suspect (...) is trying to tell me something by which items are/aren't
> listed.}

Between the parentheses are listed the mount options that are set:

    - rw       :: mounted read-write
    - nosuid   :: do not allow setting of SUID bit
                  (executables with set SUID are run as the
                  owner of the file, not the executing user)
    - nodev    :: do not allow device files (i.e. files that
                  act as an interface to a driver)
    - relatime :: update file access time only when modification
                  time is newer than access time (reduces number
                  of writes to a drive)

The rest I do not know and therefore you have to look them up yourself.

„findmnt” provides a pretty display of mounted devices and displays a
header telling you what the data in the columns refers to.

> Output of "ls -Rdl /media/richard/rco1" is
> "drwxr-xr-x 3 root root 4096 Apr 28 23:49 /media/richard/rco1".
>
> { In "drwxr-xr-x 3", what do "d" and "3" tell me? }

Programs that are part of the GNU software distribution usually have, in
addition to the terser man pages, more comprehensive info documents.
These can be accessed with the „info” program (if it is not already
installed: the Debian package goes by the same name).  For your specific
question the information can be found in the info document for the
„coreutils” package; the following command should display the
appropriate section: „info --index-search='-l <6>' coreutils”. [1]

In short: „d” denotes directories; „3” is the count of hard links.

That the man page for „ls” does not describe the output format I find
odd; might be worth a bug report (look at the „reportbug” program)?

> https://manpages.debian.org/stretch/mount/mount.8.en.html says in part:
> /begin quote
> strictatime
>     Allows to explicitly request full atime updates. This makes it
> possible for the kernel to default to relatime or noatime but still
> allow userspace to override it. For more details about the default
> system mount options see /proc/mounts.
> /end quote
>
> { Having used a file manager to look at /proc/mounts without
> comprehension, I interpreted the context of "/proc/mounts" to indicate
> that there would be a reference to it elsewhere in
> https://manpages.debian.org . Nope. }

You can read „/proc/mounts” using an editor or within the shell using a
pager, e.g. „less /proc/mounts”, or simply get it output to your
terminal using „cat /proc/mounts”.  It will show you information of the
mounts currently known by the kernel.  The output, though, is not
especially user friendly, but seems to follow the same format as
„/etc/fstab”.

What the man page's author meant by „for more details about the default
system mount options see /proc/mounts” I am not certain.  Maybe he only
wanted to say that „/proc/mounts” displays the mount options currently
applied and if you do not specify some yourself you can deduce from the
displayed options the kernel's default options?

It is a rather confusing sentence: you could file a bug report (look at
the „reportbug” program) requesting clarification.

> https://manpages.debian.org/stretch/mount/mount.8.en.html makes
> several references to "block special device".
> { "block special device" ??? }

Devices are put in two rough categories: block devices and character
devices.  Block devices are those that are partitioned into individual
accessable blocks; discs are usually considered block devices.
Character devices are all the rest: mice, keyboards, printers,
terminals.  They provide a stream of information.

> Man pages by their nature/purpose assume a certain level of expertise.
> They can be daunting for the uninitiated.

As has been mention by rhkramer for the „uninitiated” there have been
written introductory texts, though suggestions I have also not right
now.

Using a search engine usually yields good results for the more common
terms and also on Wikipedia can be found helpful computer related
articles, e.g. for block devices:
<https://en.wikipedia.org/wiki/Block_device>.

[1] Also available on the web:
    https://www.gnu.org/software/coreutils/manual/html_node/What-information-is-listed.html#index-verbose-ls-format

--
Felix Dietrich