Linux - copy file and preserve timestamp, ownership, mode:
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If you want to copy files in Linux and also want to keep or preserve the original mode or timestamp or ownership (or all) , cp command gives an option (--preserve).
From cp command man pages:
--preserve[=ATTR_LIST]
preserve the specified attributes (default: mode,ownership,timestamps) and security contexts, if possible additional attributes: links, all
Lets discuss this with some small examples.
I am logged in as user 'jk'
$ id
uid=32321(jk) gid=700(staff)
The example file tre.sh is having the following details:
$ ls -l tre.sh
-rw-r--r-- 1 jk staff 476 2009-01-13 16:20 tre.sh
Lets copy tre.sh to /tmp/tre.sh
$ cp tre.sh /tmp/tre.sh
So the timestamp is changed to the present timestamp
$ ls -l /tmp/tre.sh
-rw-r--r-- 1 jk staff 476 2009-02-05 15:10 /tmp/tre.sh
Now copy using "--preserve=timestamps" option.
$ cp --preserve=timestamps tre.sh /tmp/tre.sh.1
The original timestamp is preserved here
$ ls -l /tmp/tre.sh.1
-rw-r--r-- 1 jk staff 476 2009-01-13 16:20 /tmp/tre.sh.1
Now I just switched to root user
$ id
uid=0(root) gid=0(root) groups=0(root)
Copy tre.sh to /tmp/tre.sh.2
$ cp tre.sh /tmp/tre.sh.2
Notice the ownership and timestamp of the /tmp/tre.sh.2
$ ls -l /tmp/tre.sh.2
-rw-r--r-- 1 root root 476 2009-02-05 15:13 /tmp/tre.sh.2
You can preserve the ownership like this:
$ cp --preserve=ownership tre.sh /tmp/tre.sh.4
So /tmp/tre.sh.4 is still owned by user jk" (copied by root though)
$ ls -l /tmp/tre.sh.4
-rw-r--r-- 1 jk staff 476 2009-02-05 15:14 /tmp/tre.sh.4
Also we can specify "--preserve=ownership,timestamps" and also preserve the mode(permission) of the file with "--preserve=mode"
The cp command -p option is equivalent to --preserve=mode,ownership,timestamps
I am still 'root'; now copy using -p option
$ cp -p tre.sh /tmp/tre.sh.5
All the original attributes (mode,permission,ownership) of tre.sh is preserved.
$ ls -l /tmp/tre.sh.5
-rw-r--r-- 1 jk staff 476 2009-01-13 16:20 /tmp/tre.sh.5
