Thanks Christian.
I am using in a VirtualBox inside which I am running lxcfs
Distributor ID: Ubuntu
Description: Ubuntu 18.04.4 LTS
Release: 18.04
Codename: bionic
the source code version of lxcfs that I am using is:- 4.0.0
My objective is to prevent the OS, running inside LXC (as privileged
system container), from changing the power state of the system and in
that respect, I am trying to virtualize the file /sys/power/state
Can you kindly provide the siginificance of the following:
- What is the significance of "api_extensions"? It seems it not used
any where except as console logs as part of liblxcfs.so init function.
- Can you please explain, before calling - fuse_main(nargs, newargv,
&lxcfs_ops, opts() [in src/lxcfs.c], what is happening in the
"constructor" of liblxcfs.so [src/bindings.c] library?
I am using Ubuntu
- I have made following additions in src/bindings.h and
src/sysfs_fuse.c to show /sys/power/state in the fuse FS.
In src/bindings.h:-
-------------------
Added following:-
LXC_TYPE_SYS_POWER,
LXC_TYPE_SYS_POWER_STATE,
#define LXC_TYPE_SYS_POWER_STATE_PATH "/sys/power/state"
In src/sysfs_fuse.c:-
---------------------
Added following:-
In function:
[1] __lxcfs_fuse_ops int sys_getattr(const char *path, struct stat *sb)
#if 1
if (strcmp(path, "/sys/power") == 0) {
sb->st_mode = S_IFDIR | 00555;
sb->st_nlink = 2;
return 0;
}
if (strcmp(path, "/sys/power/state") == 0) {
sb->st_size = 0;
sb->st_mode = S_IFREG | 00444;
sb->st_nlink = 1;
return 0;
}
#endif
[2] __lxcfs_fuse_ops int sys_readdir(const char *path, void *buf,
fuse_fill_dir_t filler, off_t offset, struct fuse_file_info *fi)
#if 1
if (strcmp(path, "/sys/power") == 0) {
if (filler(buf, ".", NULL, 0) != 0 ||
filler(buf, "..", NULL, 0) != 0 ||
filler(buf, "state", NULL, 0) != 0)
return -ENOENT;
return 0;
}
#endif
[3] __lxcfs_fuse_ops int sys_open(const char *path, struct fuse_file_info *fi)
#if 1
if (strcmp(path, "/sys/power") == 0)
type = LXC_TYPE_SYS_POWER;
if (strcmp(path, "/sys/power/state") == 0)
type = LXC_TYPE_SYS_POWER_STATE;
#endif
[4] __lxcfs_fuse_ops int sys_access(const char *path, int mask)
#if 1
if (strcmp(path, "/sys/power") == 0 &&
access(path, R_OK) == 0)
return 0;
#endif
[5] __lxcfs_fuse_ops int sys_releasedir(const char *path, struct
fuse_file_info *fi)
#if 1
case LXC_TYPE_SYS_POWER:
lxcfs_info("LXC_TYPE_SYS_POWER -----%s", __func__);
break;
case LXC_TYPE_SYS_POWER_STATE:
//Need to take action here
lxcfs_info("LXC_TYPE_SYS_POWER_STATE -----%s", __func__);
break;
#endif
To run my modified liblxcfs.so, I followed these steps:-
-------------------------------------------------------
1. I stopped systemd - lxcfs.service
2. From command line, I ran lxcfs binary -
$sudo /usr/bin/lxcfs -f /var/lib/lxcfs
I verified that fuse file system got mounted at "/var/lib/lxcfs" by
running "mount" command. Here is the output of "mount" command:-
lxcfs on /var/lib/lxcfs type fuse.lxcfs
(rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other)
After this when I ran "tree" command on "/var/lib/lxcfs" -I am not
able to see /sys/power/state in the fuse file system although I could
see
/sys/devices/system/cpu/online
Is there any other file/s that I would need to modify to bring in
/sys/power/state in the FUSE FS?
Thanks and Regards,
Souvik
On 6/4/20, Christian Brauner <christian.brau...@ubuntu.com> wrote:
> On Wed, Jun 03, 2020 at 11:06:23PM +0530, Souvik Datta wrote:
>> Hello,
>> I am trying to understand the source code of LXCFS. My final objective
>> is to add /sys/power/state file as an entry. I understand the changes
>> that need to be done in sysfs_fuse.c/h to support this.
>>
>> To do this, first I am first trying to understand, how the sys entry -
>> "/sys/devices/system/cpu/online" has been added in the "target
>> directory - /var/lib/lxcfs" but I am not able to figure that out.
>>
>> Can you please give me some pointers so that I can understand how this
>> is achieved?
>
> Please take a look at:
> src/sysfs_fuse.c:sys_read()
> The enum and path used to add a file type is defined in
> src/bindings.h: enum lxcfs_virt_t
>
> and then you need to implement the actual virtualization in
> sysfs_fuse.{c,h}.
>
> Christian
> _______________________________________________
> lxc-devel mailing list
> lxc-devel@lists.linuxcontainers.org
> http://lists.linuxcontainers.org/listinfo/lxc-devel
>
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