Bug 209791 - To tunefs utilities I added flag for generate new ufsid (unique filesystem id).
Summary: To tunefs utilities I added flag for generate new ufsid (unique filesystem id).
Status: New
Alias: None
Product: Base System
Classification: Unclassified
Component: bin (show other bugs)
Version: CURRENT
Hardware: Any Any
: --- Affects Some People
Assignee: freebsd-bugs (Nobody)
URL:
Keywords: patch
Depends on:
Blocks:
 
Reported: 2016-05-27 11:43 UTC by Pavel Volkov
Modified: 2017-08-18 15:50 UTC (History)
2 users (show)

See Also:

Attachments
Added G flag. (3.18 KB, patch)
2016-05-27 11:43 UTC, Pavel Volkov 		no flags Details | Diff
View All Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description Pavel Volkov 2016-05-27 11:43:35 UTC 
Created attachment 170723 [details]
Added G flag.

In the superblock of the filesystem present unique id:

/usr/include/ufs/ffs/fs.h

/*
 * Super block for an FFS filesystem.
 */
struct fs {
...
        int32_t  fs_id[2];              /* unique filesystem id */
...

It's may by used to mount filesystem (/dev/ufsid/...).

After duplicating the disc, it is necessary to change it, to restore the uniqueness drives.
Comment 1 Pavel Volkov 2016-06-02 13:10:01 UTC 
Hello.
To generate a new ufsid I used an algorithm from a file:

/usr/src/sbin/newfs/mkfs.c

    140                 time(&utime);

    465         sblock.fs_id[0] = (long)utime;
    466         sblock.fs_id[1] = newfs_random();

   1149 /*
   1150  * For the regression test, return predictable random values.
   1151  * Otherwise use a true random number generator.
   1152  */
   1153 static u_int32_t
   1154 newfs_random(void)
   1155 {
   1156         static int nextnum = 1;
   1157
   1158         if (Rflag)
   1159                 return (nextnum++);
   1160         return (arc4random());
   1161 }
Comment 2 Pavel Volkov 2016-06-04 05:30:59 UTC 
It's patch applied to FreeBSD 11, Revision: 301300.
Comment 3 Helge Oldach 2017-08-18 15:50:08 UTC 
That's indeed the missing bit when you dd an entire partition (copying ufs meta data verbatim) - but then we need to distinguish the copied partition from the original. Thanks, please commit.