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I have two computers, my local and remote. I want to backup remote server with tar command via ssh but saving tar file on local computer. Is it possible?

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  • 1
    depending on what you are doing, you may want to look into rsync Mar 19 '15 at 14:21
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Here are two examples of what I do: one for files and one for MySQL. Both are pull solutions; your local machine logs into a remote machine and retrieves files. However, the local machine tells the remote machine to prepare the archive.

Setup & Background

I use crontab and passwordless authentication with ssh to archive and gzip on a remote machine and then direct the output of gzip to the local machine over ssh. Make sure crontab and passwordless authentication are set up. I also have some cleanup one-liners.

The benefit to this is it uses bandwidth most efficiently. The drawback is it's more resource-intensive, though on modern hardware I doubt this matters unless you're dealing with absurdly large files.

Backing up files and directories

This is probably the part you care about. Tell ssh to execute a tar and pipe to gzip on the remote machine. Have gzip write the compressed file to standard output (c flag) and direct the output to a file on your local machine.

00 00 * * * /usr/bin/ssh login@host "sudo tar -cf - -C /path/to/directory/to/backup/ file_to_back_up | gzip -9c" > /file/on/local/machine/BackUp_$(date +\%Y-\%m-\%d-\%Hh\%Mm\%Ss_\%A).tar.gz

Important: file_to_back_up is the file you are actually backing up; it can be a file or directory. It can be a series of files too: file1.txt, file2.php, etc.

The 9 flag is maximum gzip compression.

The -cf - flags and parameter create a new archive and spit the data to standard output. The -Cflag tells tar to start from a different directory than the current one. file_to_back_up can be a file or a directory. This keeps a lot of extraneous relative paths out of the archive. If you want to back up something in your home directory, I guess you can omit -C /path/to/directory/to/backup/ because ssh will by default log you into your home directory.

date +\%Y-\%m-\%d-\%Hh\%Mm\%Ss_\%A will generate a timestamp like 2015-03-19-08h58m09s_Thursday

The crontab columns 00 00 * * * basically means midnight every day.

Backing up a MySQL database

Similar to the above. The caveat is you need to make sure your mysql access can be passwordless too; the safe way to do that is with .cnf files. Skip this section if you don't use MySQL, but the concept could carry over to other tools.

30 0,13 * * * /usr/bin/ssh user@remote.host "mysqldump --defaults-file=.my.database.cnf -uroot databasename | gzip -9c" > /path/to/databasebackup_$(date +\%Y-\%m-\%d-\%Hh\%Mm\%Ss_\%A).sql.gz

The .cnf file contains login credentials so you don't have to pass them by the shell so they appear in ps for other users to see. It should contain:

[client] user=mysqluser password=yourpassword host=localhost

Depending on your setup, you may want a bunch of these for different projects/databases. If you don't, .my.cnf is used by default.

Security: you probably want to do chmod 600 *.cnf so only the owner can read and write to this file.

Cleanup

I tend to automatically delete backups older than five days with the findcommand, unless they fall on Friday. I archive Friday longer. That's why I include the day of the week in my file names.

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  • Yes, its works. But if you add sudo to remote command in crontab it will be expect that you enter password and command will be not executed. If you want to use sudo you can use it with -S option. This will tell sudo to get password from stdin: 00 00 * * * /usr/bin/ssh login@host "echo password | sudo -S tar -cf - -C /path/to/directory/to/backup/ file_to_back_up | gzip -9c" > /file/on/local/machine/BackUp_$(date +\%Y-\%m-\%d-\%Hh\%Mm\%Ss_\%A).tar.gz
    – QkiZ
    Mar 20 '15 at 10:37
  • Not good security if anyone else has access to the process list. Better that you make sudo passwordless for wheel group. As root edit /etc/sudoers and uncomment the line "%wheel ALL=(ALL) NOPASSWD: ALL" and save. Also add yourself to wheel group. For general tasks, this way you can just "sudo bash" to become root instead of "su" followed by a manual password entry.
    – Bolwerk
    Mar 20 '15 at 11:57
  • Or, even better, leave sudo out if leaving it out is an option.
    – Bolwerk
    Mar 20 '15 at 12:00
  • Or add another user, only for making backups. Add him to sudoers with strict tar command with parameters to use it without password.
    – QkiZ
    Mar 20 '15 at 16:13
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yes, some examples:

tar cvjf - * | ssh user@host "(cd /desired/path; tar xjf -)"
tar cvzf - dir/ | ssh user@host "cat > /backup/dir.tar.gz"
tar cvzf - dir/ | ssh user@host "dd of=/backup/dir.tar.gz"
ssh user@host "cat /backup/dir.tar.gz" | tar xvzf -
tar cvjf - * | ssh root@host "(cd /desired/path; tar xjf - )"

To backup remote computer and save tar on local computer

ssh user@host "(cd /desired/path; tar cvzf - *)" > /path/to/backup.tar.gz

other usage examples: https://blog.bravi.org/?p=259

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  • You have misunderstood question. Your commands make backup of local computer and extract tar on remote but I want to backup remote computer and save tar on local computer.
    – QkiZ
    Mar 19 '15 at 17:45
  • Please read the question again carefully. Your answer does not answer the original question.
    – DavidPostill
    Mar 28 '15 at 5:31
  • Right what I'm looking for when searching "tar over ssh". Thanks @floc.
    – xpt
    May 3 '16 at 23:14

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