forked from josch/mmdebstrap
Mount a new instance of /dev/pts in the chroot
Before, we bind-mounted /dev/ptmx and /dev/pts from the host into the chroot. This will make posix_openpt() fail with 'No such file or directory'. The ability to create pseudo terminals is important for apt (which will throw a warning otherwise) or running script(1) or source package testsuites like for src:util-linux. This functionality is restored by mounting a new devpts instance to /dev/pts and making /dev/ptmx a symlink to /dev/pts/ptmx. Mounting with ptmxmode=666 is required such that also non-root users in unshare mode are able to create pseudo terminals. See also: https://www.kernel.org/doc/Documentation/filesystems/devpts.txt https://salsa.debian.org/debian/schroot/-/merge_requests/2 https://bugs.debian.org/856877 https://bugs.debian.org/817236
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3 changed files with 191 additions and 5 deletions
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@ -318,3 +318,7 @@ Skip-If:
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Test: no-sbin-in-path
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Modes: fakechroot
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Test: dev-ptmx
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Modes: root unshare
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Needs-QEMU: true
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41
mmdebstrap
41
mmdebstrap
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@ -1091,6 +1091,20 @@ sub run_chroot {
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);
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next;
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}
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if ($fname eq "ptmx") {
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# We must not bind-mount ptmx from the outside or
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# otherwise posix_openpt() will fail. Instead
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# /dev/ptmx must refer to /dev/pts/ptmx either by
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# symlink or by bind-mounting. We choose a symlink.
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symlink '/dev/pts/ptmx',
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"$options->{root}/dev/ptmx"
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or error "cannot create /dev/pts/ptmx symlink";
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push @cleanup_tasks, sub {
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unlink "$options->{root}/dev/ptmx"
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or error "unlink /dev/ptmx";
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};
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next;
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}
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if (!-e "/dev/$fname") {
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warning("skipping creation of ./dev/$fname because"
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. " /dev/$fname does not exist"
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@ -1133,13 +1147,13 @@ sub run_chroot {
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. " /dev directory is missing in the target");
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next;
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}
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if (!-e "/dev/$fname") {
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if (!-e "/dev/$fname" && $fname ne "pts/") {
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warning("skipping creation of ./dev/$fname because"
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. " /dev/$fname does not exist"
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. " on the outside");
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next;
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}
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if (!-d "/dev/$fname") {
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if (!-d "/dev/$fname" && $fname ne "pts/") {
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warning("skipping creation of ./dev/$fname because"
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. " /dev/$fname on the outside is not a"
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. " directory");
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@ -1187,9 +1201,32 @@ sub run_chroot {
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"$options->{root}/dev/$fname")
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or warning("umount ./dev/$fname failed: $?");
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};
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if ($fname eq "pts/") {
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# We cannot just bind-mount /dev/pts from the host as
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# doing so will make posix_openpt() fail. Instead, we
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# need to mount a new devpts.
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# We need ptmxmode=666 because /dev/ptmx is a symlink
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# to /dev/pts/ptmx and without it posix_openpt() will
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# fail if we are not the root user.
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# See also:
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# kernel.org/doc/Documentation/filesystems/devpts.txt
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# salsa.debian.org/debian/schroot/-/merge_requests/2
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# https://bugs.debian.org/856877
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# https://bugs.debian.org/817236
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0 == system(
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'mount',
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'-t',
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'devpts',
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'none',
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"$options->{root}/dev/pts",
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'-o',
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'noexec,nosuid,uid=5,mode=620,ptmxmode=666'
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) or error "mount /dev/pts failed";
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} else {
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0 == system('mount', '-o', 'bind', "/dev/$fname",
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"$options->{root}/dev/$fname")
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or error "mount ./dev/$fname failed: $?";
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}
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} else {
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error "unsupported type: $type";
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}
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145
tests/dev-ptmx
Normal file
145
tests/dev-ptmx
Normal file
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@ -0,0 +1,145 @@
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#!/bin/sh
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set -eu
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export LC_ALL=C.UTF-8
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if [ {{ MODE }} != unshare ] && [ {{ MODE }} != root ]; then
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echo "test requires root or unshare mode" >&2
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exit 1
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fi
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if [ ! -e /mmdebstrap-testenv ]; then
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echo "this test modifies the system and should only be run inside a container" >&2
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exit 1
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fi
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if [ "$(id -u)" -eq 0 ] && ! id -u user > /dev/null 2>&1; then
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adduser --gecos user --disabled-password user
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fi
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prefix=
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[ "$(id -u)" -eq 0 ] && [ "{{ MODE }}" != "root" ] && prefix="runuser -u user --"
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# this mimics what apt does in apt-pkg/deb/dpkgpm.cc/pkgDPkgPM::StartPtyMagic()
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cat > /tmp/test.c << 'END'
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#define _GNU_SOURCE
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#include <stdlib.h>
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#include <fcntl.h>
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#include <termios.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <sys/ioctl.h>
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#include <signal.h>
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int main() {
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int ret;
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int fd = posix_openpt(O_RDWR | O_NOCTTY);
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if (fd < 0) {
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perror("posix_openpt");
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return 1;
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}
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char buf[64]; // 64 is used by apt
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ret = ptsname_r(fd, buf, sizeof(buf));
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if (ret != 0) {
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perror("ptsname_r");
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return 1;
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}
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ret = grantpt(fd);
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if (ret == -1) {
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perror("grantpt");
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return 1;
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}
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struct termios origtt;
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ret = tcgetattr(STDIN_FILENO, &origtt);
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if (ret != 0) {
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perror("tcgetattr1");
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return 1;
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}
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struct termios tt;
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ret = tcgetattr(STDOUT_FILENO, &tt);
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if (ret != 0) {
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perror("tcgetattr2");
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return 1;
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}
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struct winsize win;
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ret = ioctl(STDOUT_FILENO, TIOCGWINSZ, &win);
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if (ret < 0) {
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perror("ioctl stdout TIOCGWINSZ");
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return 1;
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}
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ret = ioctl(fd, TIOCSWINSZ, &win);
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if (ret < 0) {
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perror("ioctl fd TIOCGWINSZ");
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return 1;
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}
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ret = tcsetattr(fd, TCSANOW, &tt);
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if (ret != 0) {
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perror("tcsetattr1");
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return 1;
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}
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cfmakeraw(&tt);
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tt.c_lflag &= ~ECHO;
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tt.c_lflag |= ISIG;
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sigset_t sigmask;
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sigset_t sigmask_old;
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ret = sigemptyset(&sigmask);
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if (ret != 0) {
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perror("sigemptyset");
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return 1;
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}
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ret = sigaddset(&sigmask, SIGTTOU);
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if (ret != 0) {
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perror("sigaddset");
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return 1;
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}
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ret = sigprocmask(SIG_BLOCK,&sigmask, &sigmask_old);
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if (ret != 0) {
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perror("sigprocmask1");
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return 1;
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}
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ret = tcsetattr(STDIN_FILENO, TCSAFLUSH, &tt);
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if (ret != 0) {
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perror("tcsetattr2");
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return 1;
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}
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ret = sigprocmask(SIG_BLOCK,&sigmask_old, NULL);
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if (ret != 0) {
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perror("sigprocmask2");
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return 1;
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}
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ret = tcsetattr(STDIN_FILENO, TCSAFLUSH, &origtt);
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if (ret != 0) {
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perror("tcsetattr3");
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return 1;
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}
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return 0;
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}
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END
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# use script to create a fake tty
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# run all tests as root and as a normal user (the latter requires ptmxmode=666)
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script -qfc "$prefix {{ CMD }} --mode={{ MODE }} --variant=apt \
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--include=gcc,libc6-dev,python3 \
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--customize-hook='chroot \"\$1\" adduser --gecos user --disabled-password user' \
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--customize-hook='chroot \"\$1\" python3 -c \"import pty; print(pty.openpty())\"' \
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--customize-hook='chroot \"\$1\" runuser -u user -- python3 -c \"import pty; print(pty.openpty())\"' \
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--customize-hook='chroot \"\$1\" script -c \"echo foobar\"' \
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--customize-hook='chroot \"\$1\" runuser -u user -- env --chdir=/home/user script -c \"echo foobar\"' \
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--customize-hook='chroot \"\$1\" apt-get install --yes doc-debian 2>&1 | tee /tmp/log' \
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--customize-hook=\"copy-in /tmp/test.c /tmp\" \
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--customize-hook='chroot \"\$1\" gcc /tmp/test.c -o /tmp/test' \
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--customize-hook='chroot \"\$1\" /tmp/test' \
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--customize-hook='chroot \"\$1\" runuser -u user -- /tmp/test' \
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--customize-hook='rm \"\$1\"/tmp/test \"\$1\"/tmp/test.c' \
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{{ DIST }} /dev/null {{ MIRROR }}" /dev/null
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fail=0
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grep '^E:' /tmp/log && fail=1
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grep 'Can not write log' /tmp/log && fail=1
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grep 'posix_openpt' /tmp/log && fail=1
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grep 'No such file or directory' /tmp/log && fail=1
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if [ $fail -eq 1 ]; then
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echo "apt failed to write log:" >&2
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cat /tmp/log >&2
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exit 1
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fi
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rm /tmp/test.c /tmp/log
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