Definite's Extractor

My findings on Life, Linux, Open Source, and so on.

Category Archives: *nix

Startup Sequences of Shells

It is quite confusing if you need to work with multiple, so I make following tables.

zsh

From section STARTUP/SHUTDOWN FILES of man page zsh

Interactive Login Non-Interactive Login Interactive Non-Login Non-Interactive Non-Login
/etc/zshenv
$ZDOTDIR/.zshenv
/etc/zprofile
$ZDOTDIR/.zprofile
/etc/zshrc
$ZDOTDIR/.zshrc
/etc/zshrc
$ZDOTDIR/.zshrc
/etc/zlogin
$ZDOTDIR/.zlogin

bash

From section INVOCATION of man page bash

default

Interactive Login Non-Interactive Login Interactive Non-Login Non-Interactive Non-Login
/etc/profile

Then the first one that is readable amongst:

~/.bash_profile
~/.bash_login
~/.profile
~/.bashrc
$BASH_ENV

bash as sh

Interactive Login Non-Interactive Login Interactive Non-Login Non-Interactive Non-Login
/etc/profile
~/.profile
$ENV
$ENV

tcsh

tcsh does not seem care the interactive mode when start up. if environment version has lf, then csh.login and ~/.login will run before csh.cshrc and ~/.tcshrc, respectively.
From section Startup and shutdown of man page tcsh

Login Non-Login
/etc/csh.cshrc
/etc/csh.login
First one that is readable amongst:

~/.tcshrc
~/.cshrc
~/.history
~/.login
~/.cshdirs

^A is shown when typing Ctrl-A zsh

zsh has a nasty/convenient behaviour: it will set vi binding for you if one of environment VISUAL or EDITOR has the command start with vi.

If you don’t like this, run bindkey -e to use the emac mode instead. Put it in your zshrc.

Install Google-Chrome in OpenStack RHEL 7 instances

We have automated tests that require runnable Google Chrome. Yet the Google Chrome kept crashing.

The first encountered is:

libGL error: failed to load driver: swrast
libGL error: Try again with LIBGL_DEBUG=verbose for more details.

This one is easy, install mesa-dri-drivers solved this.

Then cames:

ERROR:sandbox_linux.cc(338)] : InitializeSandbox() called with multiple threads in process gpu-process

My initial guess was SELinux, but journalctl returns nothing about it. After a few hours, I thought, how about firefox? Maybe it helps to set the SELinux and install the missing dependencies? And… Tada, both Firefox and Google Chrome worked. Eventually, I dug out that Google Chrome requires fonts to works. Specifically, liberation-fonts-common and liberation-sans-fonts.

To sum up, following command worked for me:

sudo yum -y install mesa-dri-drivers liberation-fonts-common liberation-sans-fonts

Update for ChromeDriver user

If you are also use ChromeDriver. Be aware that ChromeDriver 2.31 and up requires libc.so.6(GLIBC_2.18), yet RHEL 7 only provide libc.so.6(GLIBC_2.17)

Jenkins: No entry currently exists in the Known Hosts file for this host

I have encountered the following error message when I was trying to connect Jenkins slave after plugin update:

[SSH] WARNING: No entry currently exists in the Known Hosts file for this host. Connections will be denied until this new host and its associated key is added to the Known Hosts file.
 Key exchange was not finished, connection is closed.
 java.io.IOException: There was a problem while connecting to xxx.xxx.xxx.xxx:22

I have tried to connect using ssh in console, it connected successfully, but Jenkins still refuse to connect.

Then I discovered that, if I provided the RSA Host key, Jenkins can now connected to slaves.

I guess the reason is ssh just use the known host key to determine whether it is known, and be able to fallback to RSA for actual authentication. On the other hand, Jenkins does not seem to have the fallback. You given RSA identity, then Jenkins expect RSA in known_hosts.

The issue is already filed as JENKINS-42959 Failed known_hosts verification for SSH agent. In the meantime you can use following workaround:

stdbuf -o0 -e0 ssh-keyscan -H <host> &>> ~/.ssh/known_hosts

The stdbuf here is for printing the stdout and stderr as the order of time they appear, just like what you would see in console. Otherwise the stderr will go first and then stdout.

Introducing Bus Factor

bmez9ovciaa7sdh

The Bus factor measures the degree of the knowledge sharing. High number means the knowledge is well shared. For example, bus factor 10 means 10 team members need to be “neutralized” to stop the project working.

This lead to the following issue: How to introduce it to your team members.
Even it is called *bus factor* does not mean you should introduce as such.

I still remember when one of my colleague explaining the idea:

Consider when you are hitting by a bus …

My real feeling on that time was:

Are you trying to curse me?

That’s right. It triggers all negative feeling and reaction. In other words, that will not help knowledge sharing.

A good way to get around this is terming it with holiday factor instead. Ah, holiday, this associate with more pleasant mood, thus make the concept much easier to be delivered and heard. And, hey, we do need to consider the impact of long holidays like Christmas and Chinese New Year.

Using holiday factor also deliver following message:

If you do not share, we may need to call you in the most inconvenient time …

So, using holiday factor is more acceptable, realistic and passive aggressive. 🙂

Yet, everything has it own limitation, and the “bus factory” is no exception. One of my respected colleague, Seth Vidal, was indeed killed in car accident, and his project, yum, is postponed. However, dnf takes its place and has been adopted by Fedora community since Fedora 22.

systemd: remember to keep the daemons alive

My sinopia daemon refused to start. After dig out the journal, I found that ExecStop run straight after ExecStart, what the…

After some research, I found that for daemons, or any other program that put themselves at the background, systemd thought they are stopped, thus stop the service for you. To prevent this, you need following in your systemd service file:

[Service]
...
RemainAfterExit=yes

so your daemons can live happily ever after.

The END

nodejs/npm yum repo for EL7

The nodejs and npm in EL7 is too old, so I borrowed the  to latest nodejs spec from  rawhide. Long story short, the result is at:

https://copr.fedorainfracloud.org/coprs/dchen/nodejs/

Please read the disclaimer and do follow the installation instruction if you choose to proceed. I don’t usually put the disclaimer like that but you need to know that:

  1. The build dependency of nodejs include openssl-1.0.2, but EL7 only shipped with 1.0.1, yet nodejs can run with openssl-1.0.1.
  2. openssl-libs is an important package, without it,  yum, curl and rpm URL install won’t work, so restore it is a bit tricky. The instruction is, however, written in the copr page.

Longer story:

To build this copr, following dependencies need to go in as well:

  1. libuv
  2. crypto-policies
  3. openssl-1.0.2

libuv is piece of cake. But crypto-policies and openssl bring the worst packager nightmare: circular dependency. After F23, crypto-policies require openssl-devel to build, yet openssl require crypto-policies to run.

I eventually dug out crypto-policies from F21 and built it, thus broke the circular dependency and finished the build.

ibus-chewing-1.5.1 Released

ibus-chewing 1.5.1 這次的更新修正了很多操作上的問題,

諸如按Ctrl-2~4 選字的功能,數字版(NumPad)的選字,以及insert 等特殊鍵的處理。

特別感謝 hiunnhue 的貢獻。他不僅提出了更好的處理數字鍵的方法,這個 release  的所有 issue 都是他修復的。再一次感謝各位參與者的意見與 pull request ,使得 ibus-chewing 更為完善。

ibus-chewing-1.5.0釋出

除了修了一些 bug 之外,這個版本有幾個亮點:

  1. 使用者可以選擇在系統匣顯示「中/英」以及「全/半」狀態,如圖:
    systray
    Gnome 3的使用者可能沒法看到,但是其他桌面環境諸如 KDE/Plasma、XFCE、LXDE、LXQT,或是支援systray的視窗管理器如 fluxbox 可以看見。
    在「中」圖示按滑鼠左鍵切換「中/英」,右鍵切換「全/半」。也可用鍵盤 shift 鍵切換「中/英」,shift-space 切換「全/半」

    啟用/停用: 進入設定畫面後,在「鍵盤(keyboard)」分頁中,選項「在系統匣中顯示圖示 (Show systray icons)」。

  2. 更好地處理 Caps Lock 及中英切換。
    現在你可以選擇是用 Shift 來切換中英,或是 Caps Lock 切換中英。
    喜歡用 Caps Lock 切換英數大小寫的使用者可以停用「Caps Lock 切換中文模式」,這樣就不用擔心輸入英文時無法用 Caps Lock 切換大小寫。

RHEL 7 mock build with staff_selinux

By default, mock won’t work with staff_selinux mode in RHEL 7. The instruction from Fedora is mostly correct, but insufficient for staff_selinux. This is because:

  1. /usr/bin/mock is now a sym-link to /usr/bin/consolehelper, thus consolehelper permission should be also allowed.
  2. The Fedora mock policy module does not have the types like staff_consolehelper_t.

There are a lot more reasons, but long story short, I have edited a policy file (PackageMaintainers_MockTricks_mock.te) that should covered the most mock usage. My SELinux skill quickly build up by editing that file. 🙂

Time for script that setup the mock, assuming you are running as root:

# getting dependencies
yum -y install selinux-policy-devel policycoreutils-python mock

# Download policy files
wget https://fedoraproject.org/w/uploads/2/2f/PackageMaintainers_MockTricks_mock.if
wget https://fedoraproject.org/w/uploads/7/73/PackageMaintainers_MockTricks_mock.fc
wget https://dchen.fedorapeople.org/files/PackageMaintainers_MockTricks_mock.te

# Build and install
make -f /usr/share/selinux/devel/Makefile
semodule -i PackageMaintainers_MockTricks_mock.pp

That’s it.

But just in case you are still getting SELinux AVC denials, you can get around yourself by using following scripts:

grep -E -e "(mock|consolehelper)" /var/log/audit/audit.log | audit2allow -M my_mock
semodule -i my_mock.pp