Libguestfs - Feb 2014 - Re: [PATCH 1/2] mllib: hostname: replace the hostname on Debian also in /etc/hosts (RHBZ#953907).

In Debian/Ubuntu systems, read the previous hostname from /etc/hostname
before replacing it, and try to carefully replace it in /etc/hosts with
the new hostname.

Since Perl_edit to edit /etc/hosts, it is added/changed as dependency
for Hostname.
---
 builder/Makefile.am |  2 +-
 mllib/Makefile.am   |  2 +-
 mllib/hostname.ml   | 22 ++++++++++++++++++++++
 sysprep/Makefile.am |  1 +
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/builder/Makefile.am b/builder/Makefile.am
index 9d2dbc5..0880e03 100644
--- a/builder/Makefile.am
+++ b/builder/Makefile.am
@@ -69,10 +69,10 @@ OBJECTS = \
 	$(top_builddir)/mllib/common_utils.cmx \
 	$(top_builddir)/mllib/urandom.cmx \
 	$(top_builddir)/mllib/random_seed.cmx \
+	$(top_builddir)/mllib/perl_edit.cmx \
 	$(top_builddir)/mllib/hostname.cmx \
 	$(top_builddir)/mllib/timezone.cmx \
 	$(top_builddir)/mllib/firstboot.cmx \
-	$(top_builddir)/mllib/perl_edit.cmx \
 	$(top_builddir)/mllib/crypt-c.o \
 	$(top_builddir)/mllib/crypt.cmx \
 	$(top_builddir)/mllib/fsync-c.o \
diff --git a/mllib/Makefile.am b/mllib/Makefile.am
index 67f0a0a..fc328d6 100644
--- a/mllib/Makefile.am
+++ b/mllib/Makefile.am
@@ -80,10 +80,10 @@ OBJECTS = \
 	common_utils.cmx \
 	urandom.cmx \
 	random_seed.cmx \
+	perl_edit.cmx \
 	hostname.cmx \
 	timezone.cmx \
 	firstboot.cmx \
-	perl_edit.cmx \
 	tTY.cmx \
 	fsync.cmx \
 	progress.cmx \
diff --git a/mllib/hostname.ml b/mllib/hostname.ml
index 6702f29..e1c5d4b 100644
--- a/mllib/hostname.ml
+++ b/mllib/hostname.ml
@@ -42,7 +42,12 @@ let rec set_hostname (g : Guestfs.guestfs) root hostname     
true
 
   | "linux", ("debian"|"ubuntu"), _ ->
+    let old_hostname = read_etc_hostname g in
     update_etc_hostname g hostname;
+    (match old_hostname with
+    | Some old_hostname -> replace_host_in_etc_hosts g old_hostname hostname
+    | None -> ()
+    );
     true
 
   | "linux",
("fedora"|"rhel"|"centos"|"scientificlinux"|"redhat-based"),
_ ->
@@ -78,3 +83,20 @@ and update_etc_hostname g hostname  
 and update_etc_machine_info g hostname    replace_line_in_file g
"/etc/machine-info" "PRETTY_HOSTNAME" hostname
+
+and read_etc_hostname g +  let filename = "/etc/hostname" in
+  if g#is_file filename then (
+    let lines = Array.to_list (g#read_lines filename) in
+    match lines with
+    | hd :: _ -> Some hd
+    | [] -> None
+  ) else
+    None
+
+and replace_host_in_etc_hosts g oldhost newhost +  let filename =
"/etc/hosts" in
+  if g#is_file filename then (
+    Perl_edit.edit_file ~debug:false g filename
+      ("s,(\\s)" ^ (Str.quote oldhost) ^ "(\\s|\\$),\\1" ^
(Str.quote newhost) ^ "\\2, if ($_ !~ /^#/)")
+  )
diff --git a/sysprep/Makefile.am b/sysprep/Makefile.am
index 4c03c7f..25cdaa5 100644
--- a/sysprep/Makefile.am
+++ b/sysprep/Makefile.am
@@ -95,6 +95,7 @@ OBJECTS = \
 	$(top_builddir)/mllib/urandom.cmx \
 	$(top_builddir)/mllib/password.cmx \
 	$(top_builddir)/mllib/random_seed.cmx \
+	$(top_builddir)/mllib/perl_edit.cmx \
 	$(top_builddir)/mllib/hostname.cmx \
 	$(top_builddir)/mllib/timezone.cmx \
 	$(top_builddir)/mllib/firstboot.cmx \
-- 
1.8.3.1

On Wed, Feb 12, 2014 at 03:30:52PM +0100, Pino Toscano
wrote:
> +and replace_host_in_etc_hosts g oldhost newhost > +  let filename =
"/etc/hosts" in
> +  if g#is_file filename then (
> +    Perl_edit.edit_file ~debug:false g filename
> +      ("s,(\\s)" ^ (Str.quote oldhost) ^
"(\\s|\\$),\\1" ^ (Str.quote newhost) ^ "\\2, if ($_ !~
/^#/)")
I'd be surprised if Str.quote can properly quote this, since
Perl regexps > the crappy regexps implemented in the Str module.

In any case I'm not convinced this is the right way to do this.

You should use Augeas instead.  It is already used in one virt-sysprep
module (sysprep/sysprep_operation_user_account.ml).

So, NACK.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top

In Debian/Ubuntu systems, read the previous hostname from /etc/hostname
before replacing it, and replace it in /etc/hosts with the new hostname.
---
 mllib/hostname.ml | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/mllib/hostname.ml b/mllib/hostname.ml
index fce16ff..0d5b5d4 100644
--- a/mllib/hostname.ml
+++ b/mllib/hostname.ml
@@ -42,7 +42,12 @@ let rec set_hostname (g : Guestfs.guestfs) root hostname     
true
 
   | "linux", ("debian"|"ubuntu"), _ ->
+    let old_hostname = read_etc_hostname g in
     update_etc_hostname g hostname;
+    (match old_hostname with
+    | Some old_hostname -> replace_host_in_etc_hosts g old_hostname hostname
+    | None -> ()
+    );
     true
 
   | "linux",
("fedora"|"rhel"|"centos"|"scientificlinux"|"redhat-based"),
_ ->
@@ -78,3 +83,25 @@ and update_etc_hostname g hostname  
 and update_etc_machine_info g hostname    replace_line_in_file g
"/etc/machine-info" "PRETTY_HOSTNAME" hostname
+
+and read_etc_hostname g +  let filename = "/etc/hostname" in
+  if g#is_file filename then (
+    let lines = Array.to_list (g#read_lines filename) in
+    match lines with
+    | hd :: _ -> Some hd
+    | [] -> None
+  ) else
+    None
+
+and replace_host_in_etc_hosts g oldhost newhost +  if g#is_file
"/etc/hosts" then (
+    let expr = "/files/etc/hosts/*[label() !=
'#comment']/*[label() != 'ipaddr'][. = '" ^ oldhost ^
"']" in
+    g#aug_init "/" 0;
+    let matches = Array.to_list (g#aug_match expr) in
+    List.iter (
+      fun m ->
+        g#aug_set m newhost
+    ) matches;
+    g#aug_save ()
+  )
-- 
1.8.3.1