Ubuntu

Ubuntu user hits thread number limit preventing SSH login

Ubuntu user hits thread number limit preventing SSH login

Recently I was investigating quite an interesting issue - there is Ubuntu based VM our testers run some tests on. It was reported they’re unable to log into the virtual machine.

After a brief investigation it became clear the issue is not network or SSH key related.

These are records from auth log:

/var/log/auth.log

Feb 28 20:21:39 test-instance sshd[21954]: pam_unix(sshd:session): session opened for user ubuntu by (uid=0)
Feb 28 20:21:39 test-instance systemd-logind[756]: New session 75 of user ubuntu.
Feb 28 20:21:39 test-instance sshd[21954]: fatal: fork of unprivileged child failed
Feb 28 20:21:39 test-instance systemd-logind[756]: Removed session 75.

Quite an obscure error message, but smells like cgroup problem. Indeed:

Don’t Rely on Ubuntu 14.04 Service Autocomplition

Don’t Rely on Ubuntu 14.04 Service Autocomplition

It appears lot of my colleagues think they’ll get the name of any service in Ubuntu system autocompleted by typing service first_few_letters_of_service_name and pressing Tab button. When this does not work (and it does not work a lot) it creates a lot of confusion and rises lot of questions.

In Ubuntu 14.04, the script that handles completions for service command is /usr/share/bash-completion/bash_completion It looks for service names as files in /etc/rc.d/init.d, /etc/init.d, and in the output of systemctl list-units --full --all

Ubuntu 14.04 Problem With Vmbuilder

Recently hit quite an annoying bug in vmbuilder, tool that allows to build Ubuntu based virtual machines.

Was trying to build a VM using the following command:

vmbuilder kvm ubuntu --suite trusty --flavour virtual --arch amd64 --mem 8192 --rootsize 8000 --dest /var/lib/libvirt/images --libvirt qemu:///system --hostname new-host --user jenkins --name jenkins --pass <jenkins_user_password> --addpkg openssh-server --addpkg git --addpkg acpid

but kernel installation failed with the following error:

Unpacking linux-image-virtual (3.13.0.53.60) ...
, stderr: grep: /proc/cpuinfo: No such file or directory
This kernel does not support a non-PAE CPU.

Ubuntu 14.04 SSH init.d Script Broken

Wasted lot of time today trying to figure out why ssh on some server still allows to log in with password despite the fact that in /etc/ssh/sshd_config password based log in is disabled:

PasswordAuthentication no