Is there a command to recreate directory trees?

Question

I created a 'cron' subdirectory in /var/log/ . It is: /var/log/cron

Within /var/log/cron I've created numerous sub-directories to store my log files for cron jobs. I am wondering if there is a way to output mkdir to match the directory structure my automated jobs use.

For example these sub-directory structure exists within

| ronshome
|-- personal_growth
| |-- building_your_relationship
| |-- fun_things_that_make_life_worth_living
| |-- hope_is_found
| |-- life_lessons
| |-- thought_of_the_day
| |-- what_makes_a_good_friend
| |-- what_my_friends_mean_to_me
| `-- who_am_i

My desired output is:

mkdir /var/log/cron/ronshome
mkdir /var/log/cron/ronshome/personal_growth
mkdir /var/log/cron/ronshome/personal_growth/building_your_relationship
mkdir /var/log/cron/ronshome/personal_growth/fun_things_that_make_life_worth_living

etc.

Essentially if I need to do a server restore I would like to be able to use this to recreate the log directories.

• Chris Davies: "if I need to do a server restore" - that's what backups are for
• Marcus Müller: @ChrisDavies I'm interpreting this as "if I need to re-provision that server"
• Peter Cordes: Note that mkdir -p can save you the trouble of recreating all the parents; you only need to give it the deepest directories. (This is not part of most good ways of solving this specific problem, just a side note.)
• jpa: Cross-site duplicate: "Copy folder structure (without files) from one location to another"
• RonJohn: @MarcusMüller re-provision? Besides, OP specifically said "restore".

Answer 1

You could just make a tar containing all the directories (not the files they contain). Something like

# if in bash, you need to enable recursive globs:
shopt -s globstar
# the trailing '/' is important! it only matches directories, not files.
tar --no-recursion -cvzf directories.tar.gz /var/log/cron/**/

then you can just extract your directories.tar.gz file to recreate the directory tree.

You could just as well use the same globbing to create a list of things to mkdir to put in a shell script, but that will put the burden of proper quoting of directory names on you, for no good reason: a tar file is specifically a file designed to allow you to recreate a directory tree from specification.

(I don't think --no-recursion is POSIX, but it's in GNU tar and bsdtar, and honestly, that's enough for any reasonably expected machine this is needed on :) )

• cas: +1. a tar file will also handle ownership and permissions of each directory, which might be useful if any of the subdirs aren't owned by root or don't have the default perms (probably 755 or 775, depending on root's umask setting).
• Stéphane Chazelas: tar is not a POSIX command. pax is the POSIX command to create tar archives.
• Andrew Henle: @StéphaneChazelas tar is not a POSIX command It used to be. GNU tar embraced, extended, and extinguished tar as a standard

Answer 2

Using mtree (available in the netbsd-mtree package on Debian), we can save a "specification" of a directory hierarchy in a text file:

$ mtree -p /var/log/cron -cd >var-log-cron.mtree

This prints the specification (-c) of the /var/log/cron directory hierarchy, omitting everything but the directories (-d) and saves it to a text file.

You can then compare another hierarchy with the stored specification using

$ mtree -f var-log-cron.mtree -p /var/log/cron -d

This would report extra or missing directories as well as metadata changes (timestamps, ownerships, filetypes).

To update the hierarchy according to the specification in the text file, use

$ mtree -f var-log-cron.mtree -p /var/log/cron -du

(Note the added -u.) This would recreate the hierarchy according to the stored specification.

• grawity: Arch doesn't have a maintained package for this (aur/nmtree appears to be abandoned), but it includes libarchive's bsdtar by default, where bsdtar -cf foo.mtree --format=mtree /var/log/cron would do the same – probably combined with Marcus's --no-recursion to exclude non-directories. (Then the same bsdtar can be used to "extract" a mtree.)

Answer 3

for a quick solution, something along the lines of

find -type d -print0 | gzip -9 > dirtree.gz
# ^ direc- ^ end 
# tories each
# only find in
# a zero-
# byte
gzip -d dirtree | xargs -0 mkdir -p 

if you don't need any information about ownership and acccess mode.

Answer 4

Based on Marcus's answer:

shopt -s globstar
printf 'mkdir %q\n' /var/log/cron/**/ > recreate.sh

will generate a sh script that will re-create the directories when run.

Bash's printf %q uses backslash escaping for its arguments. Newer Bash versions support an alternative ${var@Q} that uses quotation marks for somewhat more pleasant looking output (except when the string itself contains a single-quote, which will still be correctly processed but will look ugly); this is done at variable expansion time so it needs a temporary array variable:

shopt -s globstar
dirs=(/var/log/cron/**/)
printf 'mkdir %s\n' "${dirs[@]@Q}" > recreate.sh

Both options produce sh&bash-compatible quoting.

The external GNU Coreutils /bin/printf %q also uses single quotes (see also).

A third option (this time the output is Bash-specific) is to use declare -p to output a variable in a form that can be directly read back:

shopt -s globstar
dirs=(/var/log/cron/**/)
declare -p dirs > recreate.bash
echo 'mkdir -p "${dirs[@]}"' >> recreate.bash

• Marcus Müller: oh nice! didn't know about %q, nor about ${...@Q}. Learnt something!
• Ron Piggott: When I try the 4 line command I am getting an error message: 3: shopt: not found I put these 4 lines into a .sh file and added #!/bin/bash as line 1. Can you spot what I've done wrong?
• grawity: @RonPiggott Are you running it via sh or bash? The #!/bin/bash is correct, if you then chmod +x and run it as "./generate.sh", but e.g. if you're doing "sh generate.sh" then that negates any #! header. You specifically need bash for these commands. And more specifically I believe shopt was added in bash 1.14 whereas globstar needs bash 4.0 or later (2009).
• grawity: If you're running bash I'd suggest doing these commands one by one directly from interactive shell. They don't do much that would make it necessary to have them in separate script.
• Toby Speight: You should indicate which of Marcus's answers you're referencing - e.g. using a link.

Answer 5

rsync

You can use rsync first to include all directories and then exclude all files ^[1].

rsync -av -f"+ */" -f"- *" /path/to/src /path/to/dest/

or with older syntax ^[2]

rsync -a --include='*/' --exclude='*' source/ destination/ 

It may also work on different machines and not just locally adding user@host: e.g.

rsync -a --include='*/' --exclude='*' user1@src_host:source/ user2@dest_host:destination/ 

For more information, it is always close to us man rsync.