Package: apt
Version: 1.0.5
Severity: important
(warning: attached patch is not a solution, it is just intended to show
the problem)
Setting Dir::Cache::archives and Dir::Cache to the empty string (as
instructed by man 5 apt.conf) do NOT disable cache but set it to '/'.
Consequence: apt-get clean then effectively cleans '/' and removes all
files here.
Not true anymore but even worse, on squeeze it also removes the '/lib64'
symlink, breaking the loader and preventing any new dynamically linked
binary to be launched.
- - -
all following tests done on debian testing, up to date on 2014-07-02
current result:
debdev# cat apt.conf
Dir::Cache "";
Dir::Cache::archives "";
debdev# touch /VERY_SECRET
debdev# ls /
bin boot dev etc home initrd.img initrd.img.old lib lib64 lost+found
media mnt opt proc root run sbin srv sys tmp usr var VERY_SECRET
vmlinuz vmlinuz.old
debdev# apt-get clean
debdev# ls /
bin boot dev etc home lib lib64 lock lost+found media mnt opt proc
root run sbin srv sys tmp usr var
reading source code (contrib/configuration.cc) instead of the man page of
apt.conf:
debdev# cat apt.conf
Dir::Cache "/dev/null";
Dir::Cache::archives "/dev/null";
debdev# touch /VERY_SECRET
debdev# ls /
bin boot dev etc home lib lib64 lock lost+found media mnt opt proc
root run sbin srv sys tmp usr var VERY_SECRET
debdev# apt-get clean
debdev# ls /
bin boot dev etc home lib lib64 lock lost+found media mnt opt proc
root run sbin srv sys tmp usr var VERY_SECRET
expected result, BUT BUT BUT its not a good idea at all :
debdev# cat /etc/apt/apt.conf
Dir::Cache "/dev/null";
Dir::Cache::archives "/dev/null";
debdev# ls -l /dev/null
crw-rw-rw- 1 root root 1, 3 Jul 2 20:11 /dev/null
debdev# apt-get install libcaca
Reading package lists... Error!
E: Write error - write (28: No space left on device)
E: Can't mmap an empty file
E: Failed to truncate file - ftruncate (9: Bad file descriptor)
E: The package lists or status file could not be parsed or opened.
debdev# ls -l /dev/null
-rw-r--r-- 1 root root 0 Jul 2 20:17 /dev/null
debdev# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/debdev-root 95G 5.0G 85G 6% /
udev 10M 10M 0 100% /dev
tmpfs 202M 200K 201M 1% /run
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 403M 0 403M 0% /run/shm
/dev/sda1 228M 80M 137M 37% /boot
none 4.0K 0 4.0K 0% /sys/fs/cgroup
and finally with attached patch (built without "make test" because it has other
side-effects):
debdev# cat /etc/apt/apt.conf
Dir::Cache "";
Dir::Cache::archives "";
debdev# touch /MYTRALALA
debdev# ls /
bin dev home lib64 lost+found mnt opt root sbin sys usr
boot etc lib lock media MYTRALALA proc run srv tmp var
debdev# apt-get clean
E: Ignored empty string directory configuration (would have been expanded to
'/' otherwise)
debdev# ls /
bin dev home lib64 lost+found mnt opt root sbin sys usr
boot etc lib lock media MYTRALALA proc run srv tmp var
diff --git a/apt-pkg/contrib/configuration.cc b/apt-pkg/contrib/configuration.cc
index 00f6ad0..3dd63aa 100644
--- a/apt-pkg/contrib/configuration.cc
+++ b/apt-pkg/contrib/configuration.cc
@@ -240,6 +240,11 @@ string Configuration::FindFile(const char *Name,const char *Default) const
string Configuration::FindDir(const char *Name,const char *Default) const
{
string Res = FindFile(Name,Default);
+ if (Res == "")
+ {
+ _error->Error(_("Ignored empty string directory configuration (would have been expanded to '/' otherwise)"));
+ return Res;
+ }
if (Res.end()[-1] != '/')
{
size_t const found = Res.rfind("/dev/null");
diff --git a/doc/apt.conf.5.xml b/doc/apt.conf.5.xml
index fcbf20d..e30898c 100644
--- a/doc/apt.conf.5.xml
+++ b/doc/apt.conf.5.xml
@@ -607,8 +607,8 @@ DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
<para><literal>Dir::Cache</literal> contains locations pertaining to local cache
information, such as the two package caches <literal>srcpkgcache</literal> and
<literal>pkgcache</literal> as well as the location to place downloaded archives,
- <literal>Dir::Cache::archives</literal>. Generation of caches can be turned off
- by setting their names to the empty string. This will slow down startup but
+ <literal>Dir::Cache::archives</literal>. Generation of caches CANNOT BE TURNED OFF.
+ This would slow down startup but could
save disk space. It is probably preferable to turn off the pkgcache rather
than the srcpkgcache. Like <literal>Dir::State</literal> the default
directory is contained in <literal>Dir::Cache</literal></para>
