missing group names - unable to change group ownership

I have winscp 3.7.6
i connect to a linux box with scp (SSH2)
I have a problem changing group ownership. Specifically when viewing the properties of a file or directory, there are many missing group names missing. There are only admin, dialout, cdrom, floppy, audio, video and plugdev groups. All the others are missing.

If I view the properties of a file/directory that has another group, the group name is shown correctly.

When I try to change the group by typing in the missing group name, I get for example (the user I login with has full permission)
Command 'chgrp "www-data" "rss4j.jar"'
failed with return code 1 and error message
chgrp: changing group of `rss4j.jar': Operation not permitted.

When I try to change the group with a custom command, I get the same error

Although I'm interested only for froup memberships, the user names are missing too
Am I missing something?

stefanos wrote:

I have winscp 3.7.6
i connect to a linux box with scp (SSH2)
I have a problem changing group ownership. Specifically when viewing the properties of a file or directory, there are many missing group names missing. There are only admin, dialout, cdrom, floppy, audio, video and plugdev groups. All the others are missing.

Especially if you use SFTP protocol, WinSCP cannot know list of groups. So it will display only groups used in current directory (or maybe even of the selected files only).

When I try to change the group by typing in the missing group name, I get for example (the user I login with has full permission)
Command 'chgrp "www-data" "rss4j.jar"'
failed with return code 1 and error message
chgrp: changing group of `rss4j.jar': Operation not permitted.

When I try to change the group with a custom command, I get the same error

You probably do not have rights to change file group. On UNIX systems, you need to be file owner to change file group.

Thank you for the response, but

1) I use SCP protocol, and the groups that do show up have nothing to do with the groups actually used in the current directory

2) I'm connecting as a user who is owner and has rwx on the specific files

Stefanos

stefanos wrote:

1) I use SCP protocol, and the groups that do show up have nothing to do with the groups actually used in the current directory

Then there should be list of groups you belong to. I.e. the list of groups you can change ownership to.

2) I'm connecting as a user who is owner and has rwx on the specific files

Are you changing group to one you belong to? Are you able to change the group from SSH terminal?

martin wrote:

stefanos wrote:

1) I use SCP protocol, and the groups that do show up have nothing to do with the groups actually used in the current directory

Then there should be list of groups you belong to. I.e. the list of groups you can change ownership to.

2) I'm connecting as a user who is owner and has rwx on the specific files

Are you changing group to one you belong to? Are you able to change the group from SSH terminal?

aaa... no. I try to change group owner to a group I do NOT belong to. Why shouldn't this be possible?

aaa... no. I try to change group owner to a group I do NOT belong to. Why shouldn't this be possible?

It is POSIX rule. Some systems (like Solaris) allows overriding it.

martin wrote:

aaa... no. I try to change group owner to a group I do NOT belong to. Why shouldn't this be possible?

It is POSIX rule. Some systems (like Solaris) allows overriding it.

ok... well, I solved my problem by adding the user to the group I wanted to change to, but in general this is really confusing.

Thank you very much for your help

Stefanos