In CentOS 6.5, yum install zssh, but when I execute zssh, it gives an error showing: out of pty's.
What does this mean? How to solve this?
You can see the list of used ptys with
ls /dev/pts
The maximum number of ptys is given by
cat /proc/sys/kernel/pty/max
That value can be configured in
/etc/sysctl.conf
(see man pty)
Note that some versions of the kernel were buggy.
The ptys, or pseudo terminals are the 'channels' through which a process interacts with the user console (keyboard and screen)
There seems to be some weird library mismatch bug that cropps up in some binary distributions. See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=769366. Has not been tracked down, but a simple recompile seems to be a workaround.
Related
I'd like to run bpftrace under Ubuntu on VirtualBox.
Unfortunately, I get
$ sudo bpftrace -e 'tracepoint:syscalls:sys_enter_open { printf("%s %s\n", comm, str(args->filename)); }'
Kernel lockdown is enabled and set to 'confidentiality'. Lockdown mode blocks
parts of BPF which makes it impossible for bpftrace to function. Please see
https://github.com/iovisor/bpftrace/blob/master/INSTALL.md#disable-lockdown
for more details on lockdown and how to disable it.
Which leads me to the following instructions
1. Disable secure boot in UEFI.
As far as I can tell, there's no UEFI with VirtualBox.
2. Disable validation using mokutil, run the following command, reboot and follow the prompt.
$ sudo mokutil --disable-validation
This results in
EFI variables are not supported on this system
And
3. Use the SysRQ+x key combination to temporarily lift lockdown (until next boot)
Can't find how to do this under VirtualBox.
Any tips?
edit Apparently, #Qeole installed the same VM I did and didn't get the issue. Something must have gone wrong in my install. I tried with another VM and it now seems to work.
Leaving the issue open so that people can find this resolution.
I want to use QEMU to debug my compiled kernel linux-4.13.4 on Ubuntu 16.04.3 LTS
I follow the following steps:
1 install qemu
sudo apt-get install qemu
2 run qemu
qemu-system-x86_64 -s -S -kernel /home/wxf/kernelSources/linux-4.13.4/arch/x86_64/boot/bzImage -initrd /boot/initrd.img-4.13.4
Note:
-s shorthand for -gdb tcp::1234
-S freeze CPU at startup (use 'c' to start execution)
But I get the following warning:
warning: TCG doesn't support requested feature: CPUID.01H:ECX.vmx [bit 5]
The terminal stops there and I cannot input other commands.
The QEMU window pops up when I run it but it is stopped.
So, my question is
How to eliminate the warning and is it normal(since it is not an error information)?
Frankly speaking, I don't know how to handle that warning, can it be ignored or have you to do something with it. But I suppose the main problem is that you cannot run the VM. If so, you need to properly determine where to enter that c to start the VM. :)
QEMU has several graphical interfaces (and AFAIK can even be run in plain console). Suppose we have identical defaults for which UI to use (probably, the GTK one). When I run similar command (qemu-system-x86_64 -s -S -kernel ...), I can switch to the monitor console of QEMU by pressing Ctrl+Alt+2 (just 2, not F2). There I press c (and Enter, it seems to behave like regular terminal) and then switch to the VM display by Ctrl+Alt+1.
I had this problem, or something very similar. It gave the same warning and, while it would then boot, it was unusably slow.
I fixed it it by adding -machine ubuntu,accel=kvm to the qemu-system-x86_64 command line.
You missed out giving the RAM size to be used by the VM. The default RAM allocated by qemu is 128M, which in your case was not sufficient, I guess. Try passing
-m 512
Source
The Ubuntu 16.04 freeze by itself especially when 2-3 instance of Pycharm is actively running.I wanted to know the exact cause of the OS freeze and found linux-crashdump.
The linux-crashdump was installed using the link [kernel-crash-dump][1]
[1]: https://help.ubuntu.com/lts/serverguide/kernel-crash-dump.html "kernel-crash-dump"
It states that after installation and rebooting the system
cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-3.2.0-17-server root=/dev/mapper/PreciseS-root ro
crashkernel=384M-2G:64M,2G-:128M
But cat /proc/cmdline is not showing the parameter crashkernel added to it.
I am not able to edit the /proc/cmdline in anyway.
If I add crashkernel=384M-2G:64M,2G-:128M then the error appears.
"/proc/cmdline" E667: Fsync failed
WARNING: Original file may be lost or damaged
don't quit the editor until the file is successfully written!
I am not able to move further, as per the documentation of kernel-crash-dump after the installation, I rebooted the system, but still the crashkernel parameter in the /proc/cmdline is not appearing.
I didn't get completely what the problem was but as far as I understood you had problems with crashkernel. I think that it would help if you just remove it completely and reinstall it again, because you have lost some of the files of crashkernel and that's why it's not responding. Hope it helps :)
I am trying to install Xen on Centos6.5 based on this tutorial (http://wiki.centos.org/HowTos/Xen/Xen4QuickStart), however after installing xen and running the script to edit the grub.conf, i am not able to boot into the new kernel.
I get an error stating -
invalid magic number: 9090
Error 13: Invalid or unsupported executable format
Can someone help me please?
Current suspicion: http://wiki.centos.org/HowTos/Xen/Xen4QuickStart definitely not a 10 minute install for all platforms???
History: there is a Centos Bug on this: centos.org/print_bug_page.php?bug_id=6503
I repeated a similar process:
(1) Install Centos 6.6 (Centos kernel: 2.6.32-504.el6.x86_84) from DVD1, DVD2 with Install using only the CENTOS Repo
(2) Installed Xen (Xen4CentOS kernel:3.10.56-11.el6.centos.alt.X86_64) Issuing the following commands from the centos command line (as root, warnings from readers accepted as correct from a security standpoint) To abate the security concern, no network connection existed as an offline repo would have been used but was not actually needed for the Centos minimal install.
yum install centos-release-xen
yum install xen
/usr/bin/grub-bootxen.sh
from the Xen/Centos reference: http://wiki.centos.org/HowTos/Xen/Xen4QuickStart
I noticed that the /boot/grub/grub.conf file was non-existent and tried to reboot without it. The reference above suggests it should be there, so I am proposing that your grub.conf file was missing or incorrect because my results were similar:
'invalid magic number: 9090
Error 13: Invalid or unsupported executable format
Press any key to continue...'
So as of now I can reproduce the problem. I will be updating this as I discover what will solve it for my solution, post it with hope it fixes it for yours or others who share similar issues.
I noticed something odd, I was using a Combo USB hub and tried to reboot using the other kernel (2.6) and there were considerable failures which were squawking on the startup screen and it would not permit me to start. When I removed it I could not boot into the 3.10, but only into 2.6.
Ok, a quick find on grub.conf revealed a similar version to that shown on the reference link above in /etc. So I copied the grub.conf from /etc to /boot/grub and rebooted. But I too see similar results. The USB hub is off the system and will not be reattached, so there is something else here that needs review. I'm digging into the grub.conf file at this time...
(update) I see that there is a grub.conf file under /boot/efi/EFI/redhat. Oddly in the Centos 'bug archives' there appears to be a related resolved bug for Centos 7: bugs.centos.org/view.php?id=7242 (cannot post this as a link as my reputation is less than 10, my apologies)
Also, as this relates to magic number here are results for my type of files and magic numbers, but I have done this with vi and have some assumptions here about what I saw, so I am retrying this with the help of the other stackoverflow article which uses file-devel package LibMagic... here are the intermittent results.
File.x86_64 Magic number (if two bytes, just use first 2)
vmlinuz-2.6.32.504.el6.x86_64 /0x8c/0x8e/0x8e/0x8e
vmlinuz-3.10.56-11.el6.centos.alt.x86_64 /0x8c/0x8e/0x8e/0x8e
Note: A search of '9090' on centos.org using the provided search engine for words on the site yielded no response on 12/22/14: #wiki.centos.org/Search
There is no mention of installation problems with SELinux, even though I have set:
SELINUX=disabled
in the /etc/sysconfig/selinux file and
yum uninstall xen
yum install xen
/usr/bin/grub-bootxen.sh
No results, and no new grub file in any of the three locations listed above. /etc /boot or /boot/efi/EFI/redhat.
Comparison of the grub.conf files with other sources, show that it is reasonable. Same for the grub-bootxen.sh file based on what I could decipher from bash.
Changing the timeout in grub.conf (all I found) to 15 and removing the hiddenmenu command by #hiddenmenu, did not eliminate the '9090' error. Using: wiki.xen.org/wiki/RHEL6_Xen4_Tutorial which shows the 'kernel' modifier instead of the 'module' and changing the 'module' in front of the .img file to initrd, did not change the results.
OK. Reload.
1) reinstall minmum Centos
2) disable SE Linux
3) reboot
4) correct ifcfg-eth0 (remove NM and allow boot on startup) and service network restart
5) yum import centos-release-xen (accept import of GPG key)
6) yum install xen
7) investigate what occurs with "grub-install hd0" which produces '9090' error!
Ok, I would have to say that the question was not well defined. It is now well defined and can be posed as a question. I will convert this info and my trials to a reasonable question to see if anyone can assist with pointers...
I'm trying to install the Xeon Phi coprocessor. The specific behavior is probably related to the tools involved - my question is of a more general nature.
When I execute a command as root, I get a segmentation fault. When I execute it as root but (in my opinion unnecessarily) use sudo, it works:
i72:~ # whoami
root
i72:~ # micctrl -s
Segmentation fault
i72:~ # sudo micctrl -s
[no segfault]
What differences are there in the environments micctrl is being run in?
(Edit:) I think we ruled out environment variables as an option below.
The system is a SLES 11.2.
Thank you!
sudo removes LD_LIBRARY_PATH, LD_PRELOAD from the environment (I suspect it does it for root as well as ordinary users).
This may cause different libraries to be loaded for the program.
sudo can be configured on what variables it resets/clears - see http://brandonhutchinson.com/wiki/Sudo_and_environment_variables
Turns out that sudo just hides the "Segmentation fault" message. It still happens, but doesn't get displayed on the terminal. We found out because micctrl never gave us any output, even when it should have.
Edit: Also, if someone should run into the problem with micctrl: In our case, the Phi was not properly recognized by the system. lspci found it, but it was not listed in /sys/class/mic.