Re: understanding --idmap for containers (v2.5.0)

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On Thursday, April 20, 2017 10:44 AM, Daniel P. Berrange <berrange@xxxxxxxxxx> wrote:

> > indeed the container is using the idmap feature because the
> > efective uid/gid map (900/900) is not allowing writes in the
> > filesystem, but it doesn't seems very usefull.
> >
> > is it possible to have read/write containers while using idmap?
>
> You need to change the UIDs in your container's filesystem to be
> offset by 900

yes, that was my first thought but I was unsure if it was the correct way.

running these commands did the trick (not all files are root:root):

# find /media/containers/lab-gentoo-01 -uid 0 -exec chown --no-dereference 900 -- {}  \;

# find /media/containers/lab-gentoo-01 -gid 0 -exec chgrp --no-dereference 900 -- {}  \;

# ls -l /media/containers/lab-gentoo-01/
total 36
-rw-r--r--  1 900 900    0 Apr 20 11:16 a
drwxr-xr-x  2 900 900 4096 Apr 13 07:33 bin
drwxr-xr-x  2 900 900   18 Apr 13 03:28 boot
drwxr-xr-x  7 900 900 4096 Apr 18 12:45 dev
drwxr-xr-x 31 900 900 4096 Apr 18 12:49 etc
drwxr-xr-x  2 900 900   18 Apr 13 03:28 home
lrwxrwxrwx  1 900 900    5 Apr 13 06:13 lib -> lib64
drwxr-xr-x  2 900 900 4096 Apr 13 06:14 lib32
drwxr-xr-x  9 900 900 4096 Apr 13 07:33 lib64
drwxr-xr-x  2 900 900   18 Apr 13 03:28 media
drwxr-xr-x  2 900 900   18 Apr 13 03:28 mnt
drwxr-xr-x  2 900 900   18 Apr 13 03:28 opt
drwxr-xr-x  2 900 900    6 Apr 13 03:18 proc
drwx------  2 900 900   18 Apr 13 03:28 root
drwxr-xr-x  2 900 900   31 Apr 13 07:32 run
drwxr-xr-x  2 900 900 4096 Apr 13 07:36 sbin
drwxr-xr-x  2 900 900   18 Apr 13 03:28 sys
drwxrwxrwt  2 900 900   18 Apr 13 07:36 tmp
drwxr-xr-x 13 900 900 4096 Apr 18 12:49 usr
drwxr-xr-x  9 900 900  102 Apr 13 03:28 var

# virsh --connect lxc:/// start --console lab-gentoo-01
Domain lab-gentoo-01 started
Connected to domain lab-gentoo-01
Escape character is ^]
sh-4.3# /usr/bin/id
uid=0(root) gid=0(root) groups=0(root)

sh-4.3# pwd
/
sh-4.3# ls -la
total 40
drwxr-xr-x  21 root   root   4096 Apr 20 10:36 .
drwxr-xr-x  21 root   root   4096 Apr 20 10:36 ..
-rw-------   1 root   root     45 Apr 20 11:15 .bash_history
drwxr-xr-x   2 root   root      6 Apr 18 13:41 .oldroot
drwxr-xr-x   2 root   root   4096 Apr 13 07:33 bin
drwxr-xr-x   2 root   root     18 Apr 13 03:28 boot
drwxr-xr-x   3 root   root    320 Apr 20 11:15 dev
drwxr-xr-x  31 root   root   4096 Apr 18 12:49 etc
drwxr-xr-x   2 root   root     18 Apr 13 03:28 home
lrwxrwxrwx   1 root   root      5 Apr 13 06:13 lib -> lib64
drwxr-xr-x   2 root   root   4096 Apr 13 06:14 lib32
drwxr-xr-x   9 root   root   4096 Apr 13 07:33 lib64
drwxr-xr-x   2 root   root     18 Apr 13 03:28 media
drwxr-xr-x   2 root   root     18 Apr 13 03:28 mnt
drwxr-xr-x   2 root   root     18 Apr 13 03:28 opt
dr-xr-xr-x 249 nobody nobody    0 Apr 20 11:15 proc
drwx------   2 root   root     18 Apr 13 03:28 root
drwxr-xr-x   2 root   root     31 Apr 13 07:32 run
drwxr-xr-x   2 root   root   4096 Apr 13 07:36 sbin
dr-xr-xr-x  12 nobody nobody    0 Mar 24 23:11 sys
drwxrwxrwt   2 root   root     18 Apr 13 07:36 tmp
drwxr-xr-x  13 root   root   4096 Apr 18 12:49 usr
drwxr-xr-x   9 root   root    102 Apr 13 03:28 var
sh-4.3# touch asdf

sh-4.3#

Thank you Daniel !!

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