Quoting Barry Jaspan ([email protected]): > On Mon, Dec 15, 2014 at 2:19 PM, Serge Hallyn <[email protected]> > wrote: > > > > Since you are using / as the container rootfs, /empty is the same > > inode in the container and on the host. > > > No, it isn't. Within the container, /empty is the inode of the host's > /other_file, because /other_file is bind-mounted over /empty: > > lxc.mount.entry=/other_file empty none rw,bind 0 0
/other_file is bind-mounted *over* /empty. So /empty is busy. > host# ls -li /empty /other_file > 57876 -rw-r--r-- 1 root root 0 Dec 15 19:26 /empty > 58108 -rw-r--r-- 1 root root 0 Dec 15 19:26 /other_file > host# lxc-execute -n test -f test.config -- ls -li /empty /other_file > 58108 -rw-r--r-- 1 root root 0 Dec 15 19:26 /empty > 58108 -rw-r--r-- 1 root root 0 Dec 15 19:26 /other_file > > I would expect the host's /other_file to be busy, but not the host's /empty. > > Barry > > > > > > > > > It is over-mounted. So it > > is busy. > > > > Quoting Barry Jaspan ([email protected]): > > > I have reduced the problem I described in my previous message to a much > > > smaller test case. Here is an LXC config file that bind-mounts a single > > > file, /other_file, from the host's root filesystem on top of another > > file, > > > /empty, also from the host's root filesystem: > > > > > > lxc.console = none > > > lxc.rootfs = / > > > lxc.mount.entry=/other_file empty none rw,bind 0 0 > > > > > > While the container is running, the host's /empty cannot be unlinked: > > > > > > host# rm /empty /other_file > > > host# touch /empty /other_file > > > host# lxc-execute -n test -f test.config -- sleep 30 & > > > [1] 2419 > > > host# strace -o rm.out rm /empty > > > rm: cannot remove `/empty': Device or resource busy > > > host# grep EBUSY rm.out > > > unlinkat(AT_FDCWD, "/empty", 0) = -1 EBUSY (Device or resource > > busy) > > > host# fg > > > lxc-execute -n test -f test.config -- sleep 30 > > > ^C > > > host# rm /empty > > > host# > > > > > > Can anyone explain why the host's /empty cannot be unlinked even though > > it > > > is bind-mounted out of the running container? Why is it "busy"? > > > > > > Thanks, > > > Barry > > > > > > > > > > > > > > > On Mon, Dec 8, 2014 at 5:53 PM, Barry Jaspan <[email protected]> > > > wrote: > > > > > > > > I'm using LXC on Ubuntu 12.04 (Precise) on EC2. I am creating a > > container > > > > that uses the host's root filesystem. In the lxc config, I am > > bind-mounting > > > > a different passwd file on top of /etc/passwd: > > > > > > > > lxc.mount.entry=/container/passwd etc/passwd none rw,bind 0 0 > > > > > > > > As expected, /etc/passwd on the host and /etc/passwd in the container > > are > > > > different inodes: > > > > > > > > host# ls -i /etc/passwd > > > > 58046 /etc/passwd > > > > host# ls -i /container/passwd > > > > 287145 /container/passwd > > > > > > > > container# ls -i /etc/passwd > > > > 287145 /etc/passwd > > > > > > > > What I did not expect is that now it is not possible to unlink > > /etc/passwd > > > > at the host level (or inside the container, although I don't care about > > > > that): > > > > > > > > host# rm /etc/passwd > > > > rm: cannot remove `/etc/passwd': Device or resource busy > > > > host# chsh -s /bin/false root > > > > chsh: failure while writing changes to /etc/passwd > > > > > > > > strace confirms that unlinkat() and rename() are returning EBUSY. (chsh > > > > creates a replacement for /etc/passwd and then rename()'s it into > > place.) > > > > > > > > So, somehow, the fact that the host's /etc/passwd is *not* present in > > the > > > > container marks its inode as busy. I do not think it is as simple as > > "an > > > > inode that has been bind-mounted out of a namespace is busy" because a > > > > simple bind-mount test case does not reproduce it: > > > > > > > > # echo foo > foo > > > > # touch bar > > > > # mount --bind ./foo ./bar > > > > # cat bar > > > > foo > > > > # touch new > > > > # mv new foo > > > > # > > > > > > > > This seems related to http://lwn.net/Articles/570338/. However, in > > that > > > > article, a file which is bind-mounted into another namespace causes > > EBUSY > > > > from unlink/rename(). In my case, a file which is *not* bind-mounted > > into > > > > another namespace is causing EBUSY. > > > > > > > > Can someone explain what is going on? > > > > > > > > Thanks, > > > > > > > > Barry > > > > > > > > -- > > > > Barry Jaspan > > > > Senior Architect | Acquia <http://acquia.com> > > > > [email protected] | (c) 617.905.2208 | (w) 781-313-8298 > > > > > > > > Acquia Dev Cloud: You build killer websites. We do the rest. > > > > <http://www.acquia.com/dev-cloud> <http://acquia.com/dev-cloud> > > > > Acquia ranked #1 Software Vendor on the 2012 Inc 500 > > > > < > > http://www.acquia.com/about-us/newsroom/press-releases/inc-magazine-unveils-31st-annual-list-america-s-fastest-growing > > > > > > > > > > > > > > > > > -- > > > Barry Jaspan > > > Senior Architect | Acquia <http://acquia.com> > > > [email protected] | (c) 617.905.2208 | (w) 781-313-8298 > > > > > > Acquia Dev Cloud: You build killer websites. We do the rest. > > > <http://www.acquia.com/dev-cloud> <http://acquia.com/dev-cloud> > > > Acquia ranked #1 Software Vendor on the 2012 Inc 500 > > > < > > http://www.acquia.com/about-us/newsroom/press-releases/inc-magazine-unveils-31st-annual-list-america-s-fastest-growing > > > > > > > > _______________________________________________ > > > lxc-users mailing list > > > [email protected] > > > http://lists.linuxcontainers.org/listinfo/lxc-users > > > > _______________________________________________ > > lxc-users mailing list > > [email protected] > > http://lists.linuxcontainers.org/listinfo/lxc-users > > > > -- > Barry Jaspan > Senior Architect | Acquia <http://acquia.com> > [email protected] | (c) 617.905.2208 | (w) 781-313-8298 > > Acquia Dev Cloud: You build killer websites. We do the rest. > <http://www.acquia.com/dev-cloud> <http://acquia.com/dev-cloud> > Acquia ranked #1 Software Vendor on the 2012 Inc 500 > <http://www.acquia.com/about-us/newsroom/press-releases/inc-magazine-unveils-31st-annual-list-america-s-fastest-growing> > _______________________________________________ > lxc-users mailing list > [email protected] > http://lists.linuxcontainers.org/listinfo/lxc-users _______________________________________________ lxc-users mailing list [email protected] http://lists.linuxcontainers.org/listinfo/lxc-users
