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  • Bug#1085646: sbuild: Assumes UNSHARE_TMPDIR_TEMPLATE is mode 4777

    From Johannes Schauer Marin Rodrigues@21:1/5 to niels@thykier.net on Thu Apr 10 14:30:01 2025
    Control: tag -1 + moreinfo

    Hi,

    On Mon, 21 Oct 2024 13:25:33 +0200 Niels Thykier <niels@thykier.net> wrote:
    The sbuild code assumes that the directory hosting the

    UNSHARE_TMPDIR_TEMPLATE is mode 4777 (--chroot-mode=unshare). When it is

    not, the following rm failure will appear under cleanup



    +------------------------------------------------------------------------------+

    | Cleanup |

    +------------------------------------------------------------------------------+



    Purging /<<BUILDDIR>>

    Not cleaning session: cloned chroot in use

    rm: cannot remove '/home/user/debian/sbuild-test/tmp.sbuild.4Gf6tS2': Permission denied

    [...]



    This happens for both successful and failed builds. The temporary

    directory is properly cleaned regardless of this error (I guess there is

    rm code both on the host and "inside" the chroot).



    In my case, I changed UNSHARE_TMPDIR_TEMPLATE into a directory under my

    user's HOME folder that I just created with mkdir -p. On my system, /tmp

    is mounted with "noexec" and therefore the default could not be used.


    yes, in the code there is this comment right after the "rm -rf" runs:

    # we ignore the exit status, because the command will fail to remove the
    # unpack directory itself because of insufficient permissions

    It would be nice if there were an easy way to instruct rm to remove a directory recursively *except* for the root directory. What do you suggest should sbuild do instead? I see several options:

    * implement our own recursive removal which ignores the parent
    * redirect the rm -rf output to /dev/null to not confuse the user
    * if rm -rf fails, print a message saying that the failure is not fatal
    because there will be a rmdir on the outside which will clean the root

    Thanks!

    cheers, josch
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  • From Johannes Schauer Marin Rodrigues@21:1/5 to All on Wed Apr 23 16:10:01 2025
    Hi Niels,

    Quoting Niels Thykier (2025-04-21 22:13:32)
    Of the options presented, I would recommend the first one.

    That option has my preference because:

    A) It does not present an error to be ignored. I do not like such
    behavior since I feel it promotes error blindness. The third
    alternative fails this one in my view.

    B) It does not hide unrelated errors (that is, if another error occurs
    that message will not be hidden from the user). The second alternative
    fails this one in my view.

    I agree with your assesment. Thank you for sharing your opinion on this. While I started implementing this using Perl's remove_tree() I remembered that I already had the same problem with mmdebstrap. I now just copied what I do with mmdebstrap and recorded the reasoning behind that in the commit message:

    https://salsa.debian.org/debian/sbuild/-/merge_requests/179

    Thanks!

    cheers, josch
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