First off, my intention is to create a portable, bootable USB drive containing a GNU/Linux distribution. Specifically, I want to use Arch Linux with a squashfs read-only root filesystem.
The squashfs image is based on a snapshot of a working VM. The base system with it's services like ssh work out of the box as expected. But when trying to launch gnome via systemd (systemctl start gdm), all I see is a black screen (supposedly the X-Server started but gdm fails to load). I already tried to figure out whats happening, but failed to identify the exact problem.
Home directories are writeable
/tmp is writeable
/var/log is writeable
/var/run & /run are writeable anyway
/var/log/gdm gets created but stays empty.
Which modules may require write access to any other files? Is there any documentation? What would make sense to strace or similar?
My desire is to know the root of the problem and fix it, instead of using workarounds like unionfs. Thanks for any help or hints!
Although it's not relevant, for those who might wonder why I want to do this, here are some points to consider:
Stability - as you cannot modify system files, you cannot mess up the system (unless you write bogus directly to the drive of course)
Storage - as files are compressed, more data fits on the drive
Performance - as I/O on most USB drives is slow, compression gives you higher I/O speed
Portability - no special treatment for read-only storage, you might copy it on a CD or any other read-only technology and it will still work the same way as it would on a writeable disk
Update
I figured out that the problem was actually at /var/lib/gdm. GDM tried to access files in there an (silently) failed doing so giving me a black screen.
I figured out that the problem was actually at /var/lib/gdm. GDM tried to access files in there an (silently) failed doing so giving me a black screen.
journalctl was the debugging command i was missing in the first place.
Related
I'm in the process of building a small linux distro based on Debian for automated network testing. I am running into a pretty annoying problem though. A number of applications like paris-traceroute, ping, dublin-traceroute and so forth are not working correctly. They return an error of being unable to open a raw ICMP socket. I have tried using 'setcap cap_net_raw+ep ./application' and it's not working even though getcap indicates that the bits have been set.
I'm also running into the same problem if I try to use them as setuid root. They only work under sudo. So I'm wondering if I screwed up permissions on some intervening library or if there is some other issue.
Anyone run into something like this or have a solution?
Thanks!
In case anyone comes across this I'll explain why this is failing.
What I didn't mention is that the applications (like ping, etc) are actually installed in /opt. In this distro /opt actually and encfs file system that is only mounted after the livecd has been authorized against a licensing type of server (there are valid reasons for this - it automatically tests network connections and send the results to network engineer. We only want it to run within a specific time frame that would be associated with the user trouble ticket). So /opt isn't a real filesystem - it's an encrypted file mounted via fuse to looks like a file system. As such setcap and setuid don't actually work and likely cannot work.
My dedicated server uses debian 8 but he cant boot anymore, now i started the rescue system (sysresccd) and my question is, is it possible to edit some files on the debian drive to fix the boot problems without any data losts?
Please be more specific regarding booting issue as "not booting anymore" may have many causes.
Please post any error that appears on the screen during booting process.
To be generic, you can use this command to see all volumes:
fdisk -l
You need to mount volume containing /boot directory but without knowing particular issue it' impossible to advice further.
In my linux box, i can able to access one mount path, which is not present in /etc/fstab or /etc/mtab.
I want to disable that mount point. Please help me with the command to show the hidden mount.
Below is the hidden mount in some xxx machine.
/net/bnrdev/bld-views/build
Above path present in bnrdev machine:
/bld-views/build
These are not "hidden" per se, but NFS mounts found by your system.
You can get rid of this functionality by disabling NFS client services, or just the automount daemon.
WARNING - this will likely break automounted home directories, which could cause issues for other system users.
Please! for the LUV of all things cute & cuddly, make a copy of the files you modify. Justin Case could have an issue with your changes, right as you're falling asleep.
I need to remove some linux file - may this file is virus or some rootkit.
I understand linux in general.
I already tried rm -Rf and some other linux general command. - but I get 'operation not permited
I can not delete the file when I actulay login to the OS and when I use live ubuntu and mount the /etc/ folder.
Ubuntu has auto mount and I CAN edit any other files - except this one.
The linux permission is unknown for google.
Please your help.
That most likely has nothing to do with the file, but with the permissions you mounted the file system with. Typically live systems mount external file systems with read-only permissions, you have to manually re-mount it. The path suggests that this file is part of a partition used as a systems root partition (/) in another system which most likely you want to clean.
Consult the man pages for details about mounting.
BTW: such file permissions may well exist in a "normal" system setup, that depends on the security level chosen. I do not know this file mentioned here. I assume you now what it is for? At least you should be able to ask your software management system what package it belongs to? If it does not belong to any registered package, then indeed you should be concerned about it.
If really that file shall re deleted and you do have mounted the file system with correct (write) permissions, then there is always a "last resort" for such cases:
sudo chattr -i /<path>/sfewfesfs*
sudo rm -rf /<path>/sfewfesfs*
That should do the trick... However a general warning:
If you really have a file in that file system that does not belong there according to your software management, then deleting a single file might well not be sufficient to remove a potential thread. If you come to the conclusion that this system has indeed been hacked or targted by a root kit, then you cannot trust it any more, since obviously the attacker had full administrative rights over the system. You just have to wipe and completely setup the system again from scratch. There is no alternative to that if you came to that conclusion.
As part of my infrastructure I have many Virtual Machines running different Linux distros, under Proxmox using OpenVz. My problem is that I need to export into a personalized installable ISOs some of the VMs I have, (installable snapshots of the current state of the VMs), some of them are running Ubuntu, some of them CentOS, so my question is:
1- Is there a way I can do this aware of the OS the VM is running?,
2- Exporting VMs to ISOs the way I just explained is the way to go or is there any other approach?
I'm open to any advice from those how has experience with this subject even if I have to setup different Virt. Technology to host the VMs.
Your question is pretty vague on your requirements. I'll try to give you some ideas:
What do you mean by "Current state"? If you really want all the running processes, then you should something like VirtualBox and take a snapshot. You can easily boot that up on another computer and continue running where you left off, and it's independent of the OS.
If you really mean just the filesystem, then just copying the filesystem and burning it on a CD is unlikely to give you good results. For instance, there are many areas that are expected to be writable (/var, /tmp. even /etc for /etc/resolv.conf)
One simple idea is to just 'tar' up the filesystem, and untar it on another OpenVz distro. (I'm sure someone has made a bootable OpenVz distro..)
If you want a real bootable ISO, there are a LOT of different options. For example, you could have the kernel mount the ISO as root. Or you could boot to a RAMDisk as root, and unpack the filesystem you need. Or you could mount the ISO as root with an AUFS overlay filesystem. Or you could mount some directories as a SquashFS filesystem onto a RAM root.
But if you really want simplicity in "moving VMs around", look into Docker. It has a simple way to push a filesystem up to a public or private server, then download it on the other side, but save bandwidth on common elements like the OS and Apache installs. (If you do it right.)