Messages in this thread | | | From | "Paul Rolland" <> | Subject | Why is /dev on a different filesystem ? [Kernel 2.6.20.3] | Date | Wed, 21 Mar 2007 20:13:50 +0100 |
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Hello,
I was trying to backup a machine using tar and the --one-file-system option and I was getting an archive without /dev, but tar was spitting : /dev: file is on a different filesystem; not dumped
So, I had a look at the code in tar, and the comparison is done on the stat.st_dev field... I then wrote a simple program to stat("/", ...) and stat("/dev", ...), and got :
For / : st_dev : 769 st_ino : 2 st_mode : 16877 st_nlink : 23 st_uid : 0 st_gid : 0 st_rdev : 0 st_size : 4096
For /dev : st_dev : 15 st_ino : 1117 st_mode : 16877 st_nlink : 23 st_uid : 0 st_gid : 0 st_rdev : 0 st_size : 165580
So, obviously, tar is right... man 2 stat says : The st_dev field describes the device on which this file resides.
and df -a reports : [root@host-181 src]# df -a Filesystem 1K-blocks Used Available Use% Mounted on /dev/hda1 7936256 3105556 4421048 42% / proc 0 0 0 - /proc sysfs 0 0 0 - /sys devpts 0 0 0 - /dev/pts tmpfs 517632 0 517632 0% /dev/shm /dev/hda5 61787140 237360 58360480 1% /usr/local/witbe /dev/hda2 4956316 142292 4558192 4% /var/log none 0 0 0 - /proc/sys/fs/binfmt_misc
So, obviously, /dev is on /, but the stat(2) says no. Who is right, and where is the bug ?
Kernel 2.4 had it right : /dev was on /, no doubt.
Regards, Paul
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