Is there any standard way to have a GUI for an emulated system using qemu and chroot? I searched about 'curses' , 'qtemu' ,etc. but I don't know how to use former and the latter was buggy. any suggestions ?
I'm using this command and I'm happy with bash interface:
LANG=C sudo chroot mnt /usr/bin/qemu-arm-static -cpu cortex-a9 /bin/bash
You can always run guest machine(s) with a vncserver attached to the video console. To do this, run qemu/kvm with the -vnc option:
/usr/bin/qemu-arm-static -cpu cortex-a9 -vnc :1
This will start qemu in the background with a vncserver usually listening on "localhost:5901". You cand now start a vnc client to have access to the guest GUI.
Further info here:
http://doc.opensuse.org/products/draft/SLES/SLES-kvm_sd_draft/cha.qemu.running.html#cha.qemu.running.vnc
Related
Background
I have a Linux server running in text mode with no X installed. I intend to show video and image using directfb to the monitor (actually a TV). I have installed vlc-nox and it runs as expected if it is invoked in default console (physical keyboard).
Issue
When running it via SSH, no video is displayed, but audio is okay. The error is as below:
directfb vout display error: Cannot create primary surface
fb vout display error: cannot get terminal mode (Inappropriate ioctl for device)
core video output error: video output creation failed
core decoder error: failed to create video output
fbi's way
I think fbi also facing the same issue, as it would raise an error like below:
ioctl VT_GETSTATE: Inappropriate ioctl for device (not a linux console?)
But, fbi provides a solution for this case: -T -vt <arg> start on virtual console <arg>
So, sudo fbi -T 1 /path/to/image/file would display image as expected.
Question: What's the vlc's way?
I finally have a solution for this, so I post it here in case someone has the same question.
My understanding is that vlc needs to run under a real tty, not a pseudo tty. My solution is composed of two parts.
Part 1: Let vlc run as daemon mode.
Create a user for the daemon and assign audio and video privilege.
#useradd -c "VLC daemon" -d / -G audio,video -M -p \! -r -s /bin/false -u 75 -U vlcd
Run vlc at startup using tty1
I have tried this with unit under ubuntu.
[Unit]
Description=VLC server
After=network.target auditd.service
Conflicts=getty#tty1.service
[Service]
ExecStart=/usr/bin/vlc -I rc --rc-host 127.0.0.1:8080
ExecReload=/bin/kill -HUP $MAINPID
KillMode=process
Restart=on-failure
RestartPreventExitStatus=255
User=vlcd
Type=simple
#StandardError=tty
StandardOutput=tty
StandardInput=tty
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
Alias=vlc.service
Please take notic of the Conflicts, ExecStart, StandardInput, and StandardOutput parts.
In Conflicts, it will bypass the default getty service, otherwise it should be disable manually by #systemctrl disable getty#tty1.
In ExecStart, do not use the -d switch, which meaning that it would keep running and occupying VT 1, which is activated by Alt-F1. -rc enables the remote connect interface.
In StandardInput/Output, specify the tty as input and output device.
Part 2: Remote talk with the daemon, to let it play the file.
As --rc-host specify a local port, we need to ssh to the server first. Then, use telnet to interact (add, play, pause) with vlc.
telnet 127.0.0.1 8080
add /path/to/video/file
Im trying to debug the boot sequence of a linux kernel with qemu,
the command i'm running is:
qemu -serial stdio -kernel <path to kernel> -hda <path to rootfs> -append "root=/dev/sda terminal = ttyS0"
During boot all the kernel messages are printed to the QEMU window.
Only when the boot has finished i get my prompt back to the terminal i ran QEMU in.
Now i can start using the kernel terminal I'm running and seeing the output in the terminal and not in QEMU window.
How do i get all messages including the boot messages to my terminal and not to QEMU window (because i cant scroll up in that window..) ?
remove -serial stdio parameter
add -nographic parameter
and change the kernel parameter terminal = ttyS0 to console=ttyS0. This should do the trick.
qemu -nographic -kernel ./bzImage -hda ./image.hda -append root=/dev/sda console=ttyS0
You may want to check the script I use for kernel development: https://github.com/arapov/wrap-qemukvm (it's not very "production", but you can find useful qemu cli parameters there)
refer this Redirect Qemu console to a file or the host terminal?
to get the log on both qemu and your terminal .use
"console=ttyAMA0,115200 console=tty highres=off console=ttyS0"
Redirecting Qemu output to terminal might cause some problem (personally i don't like it). You can using options like -noframe (this will create new window but won't any window frame) or -curses to experience qemu output on terminal.
On a very simple PC, I want to replace Ubuntu 12.04 /sbin/init by the most simple bash script in order to have the very minimum number of running processes. Obviously, no X, no USB, no detection of new hardware, no upgrade, no apt, "nothing", I just need a working console with a DHCP-based Wi-Fi IP address (ssid, passphrase are already stored in /etc/network/interfaces). That's all. Currently, I have tried this in replacement of /sbin/init:
#!/bin/sh
mount -o rw,remount /
mount -t proc none /proc
udevd --daemon
mkdir /run/network
ifup -a &
while [ 1 ]; do
/sbin/getty -8 115200 tty1 vt100
done
It's working as I'm getting an IP address and I can login but:
A) While running shutdown, I get "shutdown: Unable to shutdown system:"
B) control-c is not working in the console
C) After a login, I get: "bash: cannot set terminal process group (-1): Inappropriate ioctl for device"
D) After a login, I get: "bash: no job control in this shell"
Also, I have noticed that all the user-space processes have a "?" in the tty column when running ps avx. How can I fix those problems? I don't want to use upstart in order to really control what is started on the PC and have the very bare minimum.
I ended up using Busybox init. Great tiny init...
You could leverage runlevels and based on your question runlevel 3 is what you want to use.
If you have some services that you do not wish to start, you could turn them off too for that runlevel.
For booting into runlevel 3, you just append the boot argument to the kernel in your boot loader:
<EXISTING_BOOT_CMD> 3
If your distro uses systemd instead of sysvinit, they are instead called as targets. The equivalent of runlevel 3 in systemd is usually named as multi-user.target
The kernel boot argument you would need to pass in this case is systemd.unit=multi-user.target
<EXISTING_BOOT_CMD> systemd.unit=multi-user.target
An alternative, if you do not want to touch the boot loader:
systemctl enable multi-user.target
Hello there Stack Exchange,
I'm trying to use a Raspberry Pi to make a sort of Kiosk display unit out of a TV screen. I figured that this would be a simple enough process, write a startup script that actives LXDE, x11vnc and chromium to the page I want and it's done. But unfortunately, I can't seem to get my rc.local script to work exactly as I want it too and I'm not sure why. This is the code I have added to rc.local
su pi -c startx&
su pi -c x11vnc -display :0 -q -usepw -rfbport 5901
su pi -c chromium --kiosk --incognito "http://www.springwater.ca/"
When the machine is booting it will run the startx command but not the x11vnc or chromium commands. Have I missed something here? Or am I going about this the completely wrong way?
Thanks,
Michael
It will take several seconds before the X server loads and is able to accept connections, but with your &, x11vnc and chromium will try and fail immediately.
After the startx line, you could add a simple sleep 30 to give it time to start, or maybe even poll it:
until xwininfo -root -display :0; do sleep 1; done
i use "nodm" (as package in Debian or from here: http://www.enricozini.org/sw/nodm/) on my Raspberry to login my user and start LXDE. Then autostart all needed applications as described here: http://wiki.lxde.org/en/Autostart.
Edit to answer the comment:
In Debian you can configure the user (and other things) in the file /etc/default/nodm.
I have set the parameter:
# User to autologin for
NODM_USER=dashboard
best wishes,
Matthias
I'm new to kernel development and I would like to know how to run/debug the linux kernel using QEMU and gdb. I'm actually reading Robert Love's book but unfortunately it doesn't help the reader on how to install proper tools to run or debug the kernel... So what I did was to follow this tutorial http://opensourceforu.efytimes.com/2011/02/kernel-development-debugging-using-eclipse/. I'm using eclipse as an IDE to develop on the kernel but I wanted first to get it work under QEMU/gdb. So what I did so far was:
1) To compile the kernel with:
make defconfig (then setting the CONFIG_DEBUG_INFO=y in the .config)
make -j4
2) Once the compilation is over I run Qemu using:
qemu-system-x86_64 -s -S /dev/zero -kernel /arch/x86/boot/bzImage
which launch the kernel in "stopped" state
3) Thus I have to use gdb, I try the following command:
gdb ./vmlinux
which run it correctly but... Now I don't know what to do... I know that I have to use remote debugging on the port 1234 (default port used by Qemu), using the vmlinux as the symbol table file for debugging.
So my question is: What should I do to run the kernel on Qemu, attach my debugger to it and thus, get them work together to make my life easier with kernel development.
I'd try:
(gdb) target remote localhost:1234
(gdb) continue
Using the '-s' option makes qemu listen on port tcp::1234, which you can connect to as localhost:1234 if you are on the same machine. Qemu's '-S' option makes Qemu stop execution until you give the continue command.
Best thing would probably be to have a look at a decent GDB tutorial to get along with what you are doing. This one looks quite nice.
Step-by-step procedure tested on Ubuntu 16.10 host
To get started from scratch quickly I've made a minimal fully automated QEMU + Buildroot example at: https://github.com/cirosantilli/linux-kernel-module-cheat/blob/c7bbc6029af7f4fab0a23a380d1607df0b2a3701/gdb-step-debugging.md Major steps are covered below.
First get a root filesystem rootfs.cpio.gz. If you need one, consider:
a minimal init-only executable image: https://unix.stackexchange.com/questions/122717/custom-linux-distro-that-runs-just-one-program-nothing-else/238579#238579
a Busybox interactive system: https://unix.stackexchange.com/questions/2692/what-is-the-smallest-possible-linux-implementation/203902#203902
Then on the Linux kernel:
git checkout v4.15
make mrproper
make x86_64_defconfig
cat <<EOF >.config-fragment
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_KERNEL=y
CONFIG_GDB_SCRIPTS=y
EOF
./scripts/kconfig/merge_config.sh .config .config-fragment
make -j"$(nproc)"
qemu-system-x86_64 -kernel arch/x86/boot/bzImage \
-initrd rootfs.cpio.gz -S -s \
-append nokaslr
On another terminal, from inside the Linux kernel tree, supposing you want to start debugging from start_kernel:
gdb \
-ex "add-auto-load-safe-path $(pwd)" \
-ex "file vmlinux" \
-ex 'set arch i386:x86-64:intel' \
-ex 'target remote localhost:1234' \
-ex 'break start_kernel' \
-ex 'continue' \
-ex 'disconnect' \
-ex 'set arch i386:x86-64' \
-ex 'target remote localhost:1234'
and we are done!!
For kernel modules see: How to debug Linux kernel modules with QEMU?
For Ubuntu 14.04, GDB 7.7.1, hbreak was needed, break software breakpoints were ignored. Not the case anymore in 16.10. See also: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944
The messy disconnect and what come after it are to work around the error:
Remote 'g' packet reply is too long: 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
Related threads:
https://sourceware.org/bugzilla/show_bug.cgi?id=13984 might be a GDB bug
Remote 'g' packet reply is too long
http://wiki.osdev.org/QEMU_and_GDB_in_long_mode osdev.org is as usual an awesome source for these problems
https://lists.nongnu.org/archive/html/qemu-discuss/2014-10/msg00069.html
nokaslr: https://unix.stackexchange.com/questions/397939/turning-off-kaslr-to-debug-linux-kernel-using-qemu-and-gdb/421287#421287
Known limitations:
the Linux kernel does not support (and does not even compile without patches) with -O0: How to de-optimize the Linux kernel to and compile it with -O0?
GDB 7.11 will blow your memory on some types of tab completion, even after the max-completions fix: Tab completion interrupt for large binaries Likely some corner case which was not covered in that patch. So an ulimit -Sv 500000 is a wise action before debugging. Blew up specifically when I tab completed file<tab> for the filename argument of sys_execve as in: https://stackoverflow.com/a/42290593/895245
See also:
https://github.com/torvalds/linux/blob/v4.9/Documentation/dev-tools/gdb-kernel-debugging.rst official Linux kernel "documentation"
Linux kernel live debugging, how it's done and what tools are used?
When you try to start vmlinux exe using gdb, then first thing on gdb is to issue cmds:
(gdb) target remote localhost:1234
(gdb) break start_kernel
(continue)
This will break the kernel at start_kernel.
BjoernID's answer did not really work for me. After the first continuation, no breakpoint is reached and on interrupt, I would see lines such as:
0x0000000000000000 in ?? ()
(gdb) break rapl_pmu_init
Breakpoint 1 at 0xffffffff816631e7
(gdb) c
Continuing.
^CRemote 'g' packet reply is too long: 08793000000000002988d582000000002019[..]
I guess this has something to do with different CPU modes (real mode in BIOS vs. long mode when Linux has booted). Anyway, the solution is to run QEMU first without waiting (i.e. without -S):
qemu-system-x86_64 -enable-kvm -kernel arch/x86/boot/bzImage -cpu SandyBridge -s
In my case, I needed to break at something during boot, so after some deciseconds, I ran the gdb command. If you have more time (e.g. you need to debug a module that is loaded manually), then the timing doesn't really matter.
gdb allows you to specify commands that should be run when started. This makes automation a bit easier. To connect to QEMU (which should now already be started), break on a function and continue execution, use:
gdb -ex 'target remote localhost:1234' -ex 'break rapl_pmu_init' -ex c ./vmlinux
As for me the best solution for debugging the kernel - is to use gdb from Eclipse environment. You should just set appropriate port for gdb (must be the same with one you specified in qemu launch string) in remote debugging section. Here is the manual:
http://www.sw-at.com/blog/2011/02/11/linux-kernel-development-and-debugging-using-eclipse-cdt/
On Linux systems, vmlinux is a statically linked executable file that contains
the Linux kernel in one of the object file formats supported by Linux, which
includes ELF, COFF and a.out. The vmlinux file might be required for kernel
debugging, symbol table generation or other operations, but must be made
bootable before being used as an operating system kernel by adding a multiboot
header, bootsector and setup routines.
An image of this initial root file system must be stored somewhere accessible
by the Linux bootloader to the boot firmware of the computer. This can be the
root file system itself, a boot image on an optical disc, a small partition on
a local disk (a boot paratition, usually using ext4 or FAT file systems), or a
TFTP server (on systems that can boot from Ethernet).
Compile linux kernel
Build the kernel with this series applied, enabling CONFIG_DEBUG_INFO (but leave CONFIG_DEBUG_INFO_REDUCED off)
https://www.kernel.org/doc/html/latest/admin-guide/README.html
https://wiki.archlinux.org/index.php/Kernel/Traditional_compilation
https://lwn.net/Articles/533552/
Install GDB and Qemu
sudo pacman -S gdb qemu
Create initramfs
#!/bin/bash
# Os : Arch Linux
# Kernel : 5.0.3
INIT_DIR=$(pwd)
BBOX_URL="https://busybox.net/downloads/busybox-1.30.1.tar.bz2"
BBOX_FILENAME=$(basename ${BBOX_URL})
BBOX_DIRNAME=$(basename ${BBOX_FILENAME} ".tar.bz2")
RAM_FILENAME="${INIT_DIR}/initramfs.cpio.gz"
function download_busybox {
wget -c ${BBOX_URL} 2>/dev/null
}
function compile_busybox {
tar xvf ${BBOX_FILENAME} && cd "${INIT_DIR}/${BBOX_DIRNAME}/"
echo "[*] Settings > Build options > Build static binary (no shared libs)"
echo "[!] Please enter to continue"
read tmpvar
make menuconfig && make -j2 && make install
}
function config_busybox {
cd "${INIT_DIR}/${BBOX_DIRNAME}/"
rm -rf initramfs/ && cp -rf _install/ initramfs/
rm -f initramfs/linuxrc
mkdir -p initramfs/{dev,proc,sys}
sudo cp -a /dev/{null,console,tty,tty1,tty2,tty3,tty4} initramfs/dev/
cat > "${INIT_DIR}/${BBOX_DIRNAME}/initramfs/init" << EOF
#!/bin/busybox sh
mount -t proc none /proc
mount -t sysfs none /sys
exec /sbin/init
EOF
chmod a+x initramfs/init
cd "${INIT_DIR}/${BBOX_DIRNAME}/initramfs/"
find . -print0 | cpio --null -ov --format=newc | gzip -9 > "${RAM_FILENAME}"
echo "[*] output: ${RAM_FILENAME}"
}
download_busybox
compile_busybox
config_busybox
Boot Linux Kernel With Qemu
#!/bin/bash
KER_FILENAME="/home/debug/Projects/kernelbuild/linux-5.0.3/arch/x86/boot/bzImage"
RAM_FILENAME="/home/debug/Projects/kerneldebug/initramfs.cpio.gz"
qemu-system-x86_64 -s -kernel "${KER_FILENAME}" -initrd "${RAM_FILENAME}" -nographic -append "console=ttyS0"
$ ./qemuboot_vmlinux.sh
SeaBIOS (version 1.12.0-20181126_142135-anatol)
iPXE (http://ipxe.org) 00:03.0 C980 PCI2.10 PnP PMM+07F92120+07EF2120 C980
Booting from ROM...
Probing EDD (edd=off to disable)... o
[ 0.019814] Spectre V2 : Spectre mitigation: LFENCE not serializing, switching to generic retpoline
can't run '/etc/init.d/rcS': No such file or directory
Please press Enter to activate this console.
/ # uname -a
Linux archlinux 5.0.3 #2 SMP PREEMPT Mon Mar 25 10:27:13 CST 2019 x86_64 GNU/Linux
/ #
Debug Linux Kernel With GDB
~/Projects/kernelbuild/linux-5.0.3 ➭ gdb vmlinux
...
(gdb) target remote localhost:1234
Remote debugging using localhost:1234
0xffffffff89a4b852 in ?? ()
(gdb) break start_kernel
Breakpoint 1 at 0xffffffff826ccc08
(gdb)
Display all 190 possibilities? (y or n)
(gdb) info functions
All defined functions:
Non-debugging symbols:
0xffffffff81000000 _stext
0xffffffff81000000 _text
0xffffffff81000000 startup_64
0xffffffff81000030 secondary_startup_64
0xffffffff810000e0 verify_cpu
0xffffffff810001e0 start_cpu0
0xffffffff810001f0 __startup_64
0xffffffff81000410 pvh_start_xen
0xffffffff81001000 hypercall_page
0xffffffff81001000 xen_hypercall_set_trap_table
0xffffffff81001020 xen_hypercall_mmu_update
0xffffffff81001040 xen_hypercall_set_gdt
0xffffffff81001060 xen_hypercall_stack_switch
0xffffffff81001080 xen_hypercall_set_callbacks
0xffffffff810010a0 xen_hypercall_fpu_taskswitch
0xffffffff810010c0 xen_hypercall_sched_op_compat
0xffffffff810010e0 xen_hypercall_platform_op