Libguestfs - Feb 2016 - Re: [PATCH] inspect: use /etc/hosts for detecting Linux root (RHBZ#1203898)

Use /etc/hosts instead of /etc/fstab to detect whether a partition
represents the root of a Linux installation; the latter might not exist
in smaller/special installations like Docker images.

Put an empty /etc/hosts in all the phony Linux guests to keep them
detected as we want.
---
 src/inspect-fs.c                             | 2 +-
 test-data/phony-guests/make-archlinux-img.sh | 1 +
 test-data/phony-guests/make-coreos-img.sh    | 1 +
 test-data/phony-guests/make-debian-img.sh    | 1 +
 test-data/phony-guests/make-fedora-img.pl    | 1 +
 test-data/phony-guests/make-ubuntu-img.sh    | 1 +
 6 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/inspect-fs.c b/src/inspect-fs.c
index 02fdb2a..82e1254 100644
--- a/src/inspect-fs.c
+++ b/src/inspect-fs.c
@@ -217,7 +217,7 @@ check_filesystem (guestfs_h *g, const char *mountable,
            (is_dir_bin ||
             (guestfs_is_symlink (g, "/bin") > 0 &&
              guestfs_is_dir (g, "/usr/bin") > 0)) &&
-           guestfs_is_file (g, "/etc/fstab") > 0) {
+           guestfs_is_file (g, "/etc/hosts") > 0) {
     fs->is_root = 1;
     fs->format = OS_FORMAT_INSTALLED;
     if (guestfs_int_check_linux_root (g, fs) == -1)
diff --git a/test-data/phony-guests/make-archlinux-img.sh
b/test-data/phony-guests/make-archlinux-img.sh
index 066df09..f748171 100755
--- a/test-data/phony-guests/make-archlinux-img.sh
+++ b/test-data/phony-guests/make-archlinux-img.sh
@@ -45,6 +45,7 @@ mkdir-p /var/lib/pacman/local/test-package-1:0.1-1
 
 write /etc/fstab "/dev/sda1 / ext4 rw,relatime,data=ordered 0 1"
 touch /etc/arch-release
+touch /etc/hosts
 write /etc/hostname "archlinux.test"
 
 upload $SRCDIR/archlinux-package
/var/lib/pacman/local/test-package-1:0.1-1/desc
diff --git a/test-data/phony-guests/make-coreos-img.sh
b/test-data/phony-guests/make-coreos-img.sh
index 1de2f25..e229926 100755
--- a/test-data/phony-guests/make-coreos-img.sh
+++ b/test-data/phony-guests/make-coreos-img.sh
@@ -76,6 +76,7 @@ write /etc/coreos/update.conf "GROUP=stable"
 upload archlinux.release /usr/share/coreos/lsb-release
 ln-s ../usr/share/coreos/lsb-release /etc/lsb-release
 write /etc/hostname "coreos.invalid"
+touch /etc/hosts
 
 EOF
 
diff --git a/test-data/phony-guests/make-debian-img.sh
b/test-data/phony-guests/make-debian-img.sh
index 637bd4b..0b4f75e 100755
--- a/test-data/phony-guests/make-debian-img.sh
+++ b/test-data/phony-guests/make-debian-img.sh
@@ -81,6 +81,7 @@ mkdir /var/log
 upload debian.fstab /etc/fstab
 write /etc/debian_version "5.0.1"
 write /etc/hostname "debian.invalid"
+touch /etc/hosts
 
 upload $SRCDIR/debian-packages /var/lib/dpkg/status
 
diff --git a/test-data/phony-guests/make-fedora-img.pl
b/test-data/phony-guests/make-fedora-img.pl
index 192f48f..b1098ba 100755
--- a/test-data/phony-guests/make-fedora-img.pl
+++ b/test-data/phony-guests/make-fedora-img.pl
@@ -211,6 +211,7 @@ $g->write ('/etc/motd', "Welcome to Fedora
release 14 (Phony)\n");
 $g->write ('/etc/redhat-release', 'Fedora release 14
(Phony)');
 $g->write ('/etc/fedora-release', 'Fedora release 14
(Phony)');
 $g->write ('/etc/sysconfig/network',
'HOSTNAME=fedora.invalid');
+$g->touch ('/etc/hosts');
 
 if (-f "fedora.mdadm") {
   $g->upload ("fedora.mdadm", '/etc/mdadm.conf');
diff --git a/test-data/phony-guests/make-ubuntu-img.sh
b/test-data/phony-guests/make-ubuntu-img.sh
index a3aa610..b49e8ff 100755
--- a/test-data/phony-guests/make-ubuntu-img.sh
+++ b/test-data/phony-guests/make-ubuntu-img.sh
@@ -72,6 +72,7 @@ upload ubuntu.fstab /etc/fstab
 write /etc/debian_version "5.0.1"
 upload ubuntu.release /etc/lsb-release
 write /etc/hostname "ubuntu.invalid"
+touch /etc/hosts
 
 upload $SRCDIR/debian-packages /var/lib/dpkg/status
 
-- 
2.5.0

On Wednesday 24 February 2016 15:43:40 Pino Toscano
wrote:
> Use /etc/hosts instead of /etc/fstab to detect whether a partition
> represents the root of a Linux installation; the latter might not exist
> in smaller/special installations like Docker images.
> 
> Put an empty /etc/hosts in all the phony Linux guests to keep them
> detected as we want.
> ---
Discard this version, I'll send a more safe version.

-- 
Pino Toscano

On Wed, Feb 24, 2016 at 03:43:40PM +0100, Pino Toscano
wrote:
> Use /etc/hosts instead of /etc/fstab to detect whether a partition
> represents the root of a Linux installation; the latter might not exist
> in smaller/special installations like Docker images.
IMHO /etc/hosts is just as unreliable as /etc/fstab.

I'd rather test for /bin/sh being present and being an ELF executable or
shared object.

Roman.

On Wednesday 24 February 2016 20:05:35 Roman Kagan
wrote:
> On Wed, Feb 24, 2016 at 03:43:40PM +0100, Pino Toscano wrote:
> > Use /etc/hosts instead of /etc/fstab to detect whether a partition
> > represents the root of a Linux installation; the latter might not
exist
> > in smaller/special installations like Docker images.
> 
> IMHO /etc/hosts is just as unreliable as /etc/fstab.
> 
> I'd rather test for /bin/sh being present and being an ELF executable
or
> shared object.
That won't work with recent Fedora/RHEL/CentOS systems due to the
UsrMerge: if /usr is in a separate partition, /bin/sh "exists" there
too, and thus that partition would be detected as root.

-- 
Pino Toscano

On Wed, Feb 24, 2016 at 05:31:06PM +0100, Pino Toscano
wrote:
> On Wednesday 24 February 2016 15:43:40 Pino Toscano wrote:
> > Use /etc/hosts instead of /etc/fstab to detect whether a partition
> > represents the root of a Linux installation; the latter might not
exist
> > in smaller/special installations like Docker images.
> > 
> > Put an empty /etc/hosts in all the phony Linux guests to keep them
> > detected as we want.
> > ---
> 
> Discard this version, I'll send a more safe version.
What about /etc/services?  That's been available on every Unix since
4.2BSD (released in 1983).  On Fedora it's part of the 'setup'
package.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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