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I'm looking for a Linux command that can change ownership of all files belonging to a given user, preferably in a targeted directory, to another specified user.

My dream command would look something like this...

chuser -R --olduser tom --newuser jerry

or

chuser -R --olduser 1066 --newuser 1492

This is my scenario... I have a backup file (.tgz) with user and group information preserved in it. It was taken from a web server running Apache and MySQL. The files in the backup are from across the system and contain files from several different users and several system type accounts and it is key that when restored on the new server the settings are not lost. The problem is that the users on the machine the files are being restored to don't match the ones in the backup file. For instance both machines had a MySQL user but they have different user ids and there are several user ids that existed on both machines that belong to different users. This means there is no way to sync the users on the new machine to the ones on the old machine.

I can find all the users files with the find command like this...

find /decompressed-backup-dir -uid 1050

or

find /decompressed-backup-dir -user tom

If, as I suspect, there is no way to do what I want with a single command then perhaps there is a way to pipe the results of the find command to another command to handle the ownership change?

I could do this with a PHP script but there are 4GB and tens of thousands of files in the backup so I don't want to use PHP or Perl but I would be happy with a shell script that could handle it.

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migrated from stackoverflow.com Jul 20 '11 at 4:36

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5 Answers 5

up vote 16 down vote accepted

Something like

find /decompressed-backup-dir -uid 1050 -exec chown newuser:newgroup {} +
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I think the --from flag on chown command is probably the easiest way.

chown --from=oldguy newguy * -R
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Best solution, no need to find love it –  Tobias Hagenbeek Jul 16 at 15:29

You can use find, as some one else posted, to do the chown. However, you may not have to as tar will take care of things for you. For example, if you make a tar on machine A where user tom is uid 500 and then untar the file on machine B where user tom is uid 505, tar will do the right thing and make the files owned by uid 505.

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Interesting tidbit, I was not aware of this. So tar not only stores the uid but also the name associated with the uid. –  Nicholi Jul 20 '11 at 20:23
2  
The original tar format only stored the numeric information. The UStar format, introduced by POSIX in the late '80s, adds the names. So pretty much any tar you encounter these days does the right thing. –  Ciclamino Jul 22 '11 at 21:02

The answer sets both user and group:

find /decompressed-backup-dir -uid 1050 -exec chown newuser:newgroup {} +

but if you want to change ONLY group of files that belongs to some user you cannot use chown (as far as I know), but instead use chgrp:

find /decompressed-backup-dir -uid 1050 -exec chgrp newgroup {} +

and to change ONLY group of files that belongs to some group you have to use eg.:

find /decompressed-backup-dir -gid 400 -exec chgrp newgroup {} +

Just to add knowledge.

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Actually, you can just leave out the newuser part. Man page says: "If the colon and group are given, but the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp." –  Ben Voigt Feb 26 at 1:22

You can use chown - R /directory/file

This command will change permission for all instance of the directory chown - R /directory

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