2:13 a.m.
There are some linux systems in the wild where the /etc/hostname file
does not contain the configured hostname as sole line in that file. This
file actually allows for comments [1] starting with "#" and the original
logic would extract the comment line instead of the hostname on such
systems. This patch fixes this by filtering out the comment lines and
any empty lines.
[1] https://www.freedesktop.org/software/systemd/man/hostname.html
---
Please keep in mind that this is my first attempt at OCaml after taking
a quick crash-course to get familiar with the language to produce this
patch. Therefore, the patch may be very suboptimal and break guidelines,
so please be forgiving :-)
daemon/inspect_fs_unix.ml | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/daemon/inspect_fs_unix.ml b/daemon/inspect_fs_unix.ml
index 63cb279d0..533ef71b2 100644
--- a/daemon/inspect_fs_unix.ml
+++ b/daemon/inspect_fs_unix.ml
@@ -556,11 +556,23 @@ and check_hostname_from_file filename =
let chroot =
let name = sprintf "check_hostname_from_file: %s" filename in
Chroot.create ~name () in
-
- let hostname = Chroot.f chroot read_small_file filename in
- match hostname with
- | None | Some [] | Some [""] -> None
- | Some (hostname :: _) -> Some hostname
+ try
+ let lines = Chroot.f chroot read_small_file filename in
+ let lines = match lines with
+ | None -> raise Not_found
+ | Some lines -> List.map String.trim lines in
+ let rec loop = function
+ | [] -> raise Not_found
+ | line :: _ when String.length line > 0 &&
+ not (String.is_prefix line "#") ->
+ line
+ | _ :: lines ->
+ loop lines
+ in
+ let hostname = loop lines in
+ Some hostname
+ with
+ Not_found -> None
(* Parse the hostname from /etc/sysconfig/network. This must be
* called from the 'with_augeas' wrapper. Note that F18+ and
--
2.36.1
6:45 a.m.
How about this instead?
It actually changes the behaviour slightly. Currently a /etc/hostname
which contains the single character '\n' would return
inspect_get_hostname = "" (which seems wrong). This is the default
/etc/hostname for virt-builder images.
I think this is because in the current code, read_small_file actually
returns “Some [""; ""]”, so it takes the branch where it matches
“| Some (hostname :: _)” which returns empty string.
Anyway, after this patch it returns "unknown" which is documented as
"the hostname could not be determined", which I think is more correct
behaviour. I tested it also on files with blank lines and comments
and so on, and it seems to do what is necessary, although it could do
with a proper regression test.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html
6:59 a.m.
On 07/20/22 13:45, Richard W.M. Jones wrote:
How about this instead?
It actually changes the behaviour slightly. Currently a /etc/hostname
which contains the single character '\n' would return
inspect_get_hostname = "" (which seems wrong). This is the default
/etc/hostname for virt-builder images.
I think this is because in the current code, read_small_file actually
returns “Some [""; ""]”, so it takes the branch where it matches
“| Some (hostname :: _)” which returns empty string.
Anyway, after this patch it returns "unknown" which is documented as
"the hostname could not be determined", which I think is more correct
behaviour. I tested it also on files with blank lines and comments
and so on, and it seems to do what is necessary, although it could do
with a proper regression test.
Rich.
-- Richard Jones, Virtualization Group, Red Hat
http://people.redhat.com/~rjones Read my programming and virtualization
blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from
scratch http://libguestfs.org/virt-builder.1.html
0001-daemon-Parse-etc-hostname-files-containing-comments.patch
From 3b6897c8ba9c8d438e8599af93188e65cced6ec8 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones(a)redhat.com>
Date: Wed, 20 Jul 2022 12:33:09 +0100
Subject: [PATCH] daemon: Parse /etc/hostname files containing comments
Thanks: Dawid Zamirski
Link: https://www.freedesktop.org/software/systemd/man/hostname.html
---
daemon/inspect_fs_unix.ml | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/daemon/inspect_fs_unix.ml b/daemon/inspect_fs_unix.ml
index 63cb279d08..8045ef0d43 100644
--- a/daemon/inspect_fs_unix.ml
+++ b/daemon/inspect_fs_unix.ml
@@ -551,15 +551,28 @@ and check_hostname_linux () =
else
None
-(* Parse the hostname where it is stored directly in a file. *)
+(* Parse the hostname where it is stored directly in a file.
+ *
+ * For /etc/hostname:
+ * "The file should contain a single newline-terminated hostname
+ * string. Comments (lines starting with a "#") are ignored."
+ * [https://www.freedesktop.org/software/systemd/man/hostname.html]
+ *
+ * For other hostname files the exact format is not clear, but
+ * hostnames cannot begin with "#" and cannot be empty, so ignoring
+ * those lines seems safe.
+ *)
and check_hostname_from_file filename =
let chroot =
let name = sprintf "check_hostname_from_file: %s" filename in
Chroot.create ~name () in
let hostname = Chroot.f chroot read_small_file filename in
- match hostname with
- | None | Some [] | Some [""] -> None
+
+ let keep_line line = line <> "" && not (String.is_prefix line
"#") in
+ let lines = Option.map (List.filter keep_line) hostname in
+ match lines with
+ | None | Some [] -> None
| Some (hostname :: _) -> Some hostname
(* Parse the hostname from /etc/sysconfig/network. This must be
-- 2.37.0.rc2
Acked-by: Laszlo Ersek <lersek(a)redhat.com>
12:36 p.m.
On Wed, 2022-07-20 at 12:45 +0100, Richard W.M. Jones wrote:
How about this instead?
It actually changes the behaviour slightly. Currently a
/etc/hostname
which contains the single character '\n' would return
inspect_get_hostname = "" (which seems wrong). This is the default
/etc/hostname for virt-builder images.
I think this is because in the current code, read_small_file actually
returns “Some [""; ""]”, so it takes the branch where it matches
“| Some (hostname :: _)” which returns empty string.
Anyway, after this patch it returns "unknown" which is documented as
"the hostname could not be determined", which I think is more correct
behaviour. I tested it also on files with blank lines and comments
and so on, and it seems to do what is necessary, although it could do
with a proper regression test.
Rich.
Works great for me and looks much more elegant that what I came up
with.
Thanks,
Dawid
1:47 p.m.
On Wed, Jul 20, 2022 at 01:36:25PM -0400, dzrudy(a)gmail.com wrote:
On Wed, 2022-07-20 at 12:45 +0100, Richard W.M. Jones wrote:
> How about this instead?
>
> It actually changes the behaviour slightly. Currently a
> /etc/hostname
> which contains the single character '\n' would return
> inspect_get_hostname = "" (which seems wrong). This is the default
> /etc/hostname for virt-builder images.
>
> I think this is because in the current code, read_small_file actually
> returns “Some [""; ""]”, so it takes the branch where it
matches
> “| Some (hostname :: _)” which returns empty string.
>
> Anyway, after this patch it returns "unknown" which is documented as
> "the hostname could not be determined", which I think is more correct
> behaviour. I tested it also on files with blank lines and comments
> and so on, and it seems to do what is necessary, although it could do
> with a proper regression test.
>
> Rich.
>
Works great for me and looks much more elegant that what I came up
with.
Thanks - this is upstream commit 4a517601c752955e35b472ea127cb4b7330a6136
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v
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4 comments
4 participants
participants (4)
-
Dawid Zamirski -
dzrudy＠gmail.com
-
Laszlo Ersek -
Richard W.M. Jones