I would like to append the dates to these backups that I'm going to do (thus keeping more than one save) and then automatically delete all previous backups except the last n in chronological order.
Is it possible to do this from the terminal, perhaps through an option of rm? Or maybe through a script? Or maybe via an rsync function?

rsync can do differential backups, eg.:

rsync -a --delete --quiet --inplace --backup --backup-dir=/location/to/backup/incr/$DAY /path/to/backup/ /location/to/backup/full/

Last edited by sabroad (2021-06-04 08:27:56)

Arciere · 2021-06-04 08:55:14

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Last edited by Arciere (2025-04-30 08:35:47)

Arciere · 2021-06-04 08:58:54

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Arciere · 2021-06-04 09:25:36

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lambdarch · 2021-06-04 09:25:40

Arciere wrote:

I built the following formatting to attribute to the files for my backups:
filename$$(date +%d-%m-%Y_%H:%M:%S)$
The result is the following:
filename(31-12-2020_17:46:59)
Could this be fine or should I format them in US format, for example?

You'd better prefix the filenames by a date in a naturally sortable format, like this:

$(date +%Y-%m-%d_%H:%M:%S)-filename

Then you work with an array:

files=(/backup/dir/*)
n_files=${#files[@]}
for ((n = 0; n < n_files - n_to_keep; n++)); do
  rm "${files[-1-n]}"
done

where n_to_keep is the number of files you want to keep, to define (not tested: prefix rm with echo before trying this ).

Arciere · 2021-06-04 09:33:07

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Last edited by Arciere (2025-04-30 08:35:23)

lambdarch · 2021-06-04 09:53:41

Yes, that's it, that's how we usually do it.
For your questions about arrays, see man bash
The line

files=(/backup/dir/*)

is a way to set up an array.

Arciere · 2021-06-04 09:56:56

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Last edited by Arciere (2025-04-30 08:35:13)

lambdarch · 2021-06-04 10:01:47

The language is bash ^^
"most practical" I don't know: this is a (bash-builtin) way to do it when files are named correctly.

Trilby · 2021-06-04 13:10:48

If you'd be happy deleting files older than a specific date or number of days old (rather than keeping 'n' files) just use find:

find $path_to_backups -mtime +$days

When you have replaced the path and days variables, understand what the command does, and are satisfied with the resulting list of deletion candidates, just run the command again appending the flag '-delete'.

I'd also suggest if you are going to continue using arch linux that you invest some time in learning about your system. I'd strongly advise working through the "linux tutorial" and "bash scripting" guides here: https://ryanstutorials.net/

Last edited by Trilby (2021-06-04 13:12:14)

Slithery · 2021-06-04 13:23:02

I just use rsnapshot.

Arciere · 2021-06-04 16:56:54

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Last edited by Arciere (2025-04-30 08:35:04)

lambdarch · 2021-06-04 17:25:51

It's brittle to use ls: you don't control the output format, it's not made for that.
If you want to use an external command, use find instead:

find /backupFolder -print0 | sort -z | tail -z -n+11 | xargs -0 rm -rfv

Last edited by lambdarch (2021-06-04 17:36:21)

Arciere · 2021-06-04 17:46:22

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Last edited by Arciere (2025-04-30 08:34:55)

lambdarch · 2021-06-04 17:53:19

The filenames can contain spaces, special characters and so on: that's why ls is a bad idea (this is a little mentioned in the link you quote by the way).

In fact there is no need for find here:

printf '%s\0' /backupFolder/* | tail -z -n+11 | xargs -0 rm -rfv

EDIT: I didn't see the -d in your ls: in this case, it's probably better to use find as above, adding -type d, and maybe -maxdepth 1.
To summarize, this would give:

find /backupFolder -maxdepth 1 -type d -print0 | sort -z | tail -z -n+11 | xargs -0 rm -rfv

Last edited by lambdarch (2021-06-04 18:05:18)

Arciere · 2021-06-06 07:22:39

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Last edited by Arciere (2025-04-30 08:34:47)

Arciere · 2021-06-06 07:58:14

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Last edited by Arciere (2025-04-30 08:34:37)

lambdarch · 2021-06-06 10:40:51

Well, it depends on what you really want to do in the end: list directories or not, search depth, etc.
In any case, it is useless to concatenate commands like that: if you use find, filter as much as you can with its options, then sort the result (if needed and only once), select some lines (if needed and only once), and finally act on these lines.

As you describe your need in #18, it seems to me that find is unnecessary:

printf '%s\0' /backupFolder/* | tail -z -n+11 | xargs -0 rm -rfv

should do the job.

You can replace rm -rfv with printf '%s\n' to see what it gives.
On a small example:

$ ls -l ./
total 0
-rw-r--r-- 1 user user 0  6 juin  12:35 20210601-filemane
-rw-r--r-- 1 user user 0  6 juin  12:35 20210602-filemane
-rw-r--r-- 1 user user 0  6 juin  12:35 20210603-filemane
-rw-r--r-- 1 user user 0  6 juin  12:35 20210604-filemane
-rw-r--r-- 1 user user 0  6 juin  12:35 20210605-filemane
-rw-r--r-- 1 user user 0  6 juin  12:35 20210606-filemane
-rw-r--r-- 1 user user 0  6 juin  12:35 20210607-filemane
-rw-r--r-- 1 user user 0  6 juin  12:35 20210608-filemane
-rw-r--r-- 1 user user 0  6 juin  12:35 20210609-filemane
$ printf '%s\0' ./* | tail -z -n+5 | xargs -0 printf '%s\n'
./20210605-filemane
./20210606-filemane
./20210607-filemane
./20210608-filemane
./20210609-filemane
$

Arciere · 2021-06-06 12:56:43

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Last edited by Arciere (2025-04-30 08:34:26)

Trilby · 2021-06-06 13:47:33

Arciere wrote:

But as for the -z option next to both sort and tail I'm not finding anything: what are they for?

How are you not finding anything? You're clearly not looking. It is very clearly covered in the man pages for each of these tools.

Arciere · 2021-06-06 13:49:33

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Last edited by Arciere (2025-04-30 08:34:16)

Arciere · 2021-06-06 13:51:53

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Last edited by Arciere (2025-04-30 08:34:09)

Trilby · 2021-06-06 13:58:01

If the input you are `sort'ing or 'tail'ing is delineated by NULL rather than newline, then yes, that's precisely what that flag is for. Otherwise `sort` will just receive one line of input, so there is nothing to sort and it will output exactly what it was given as input completely unchanged.

Of course, you could quite easily test this yourself rather than asking.

You are expected to read man pages, and make an effort to learn on your own.

Do not take on "help vampire" habits.

Last edited by Trilby (2021-06-06 13:59:15)

Arch Linux

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