IT notes

In macOS, to find a path of an application, for example Chromium: $ osascript -e 'POSIX path of (path to application "Chromium")' …

To periodically check status of the cluster, create a script (/tmp/xx): #!/bin/sh mysql -e \ "SHOW GLOBAL STATUS WHERE Variable_name IN ( 'wsrep_cert_deps_distance', 'wsrep_cluster_size', 'wsrep_cluster_status', 'wsrep_connected', 'wsrep_evs_delayed', 'wsrep_flow_control_paused', 'wsrep_flow_control_paused_ns', 'wsrep_flow_control_recv', 'wsrep_flow_control_sent', 'wsrep_local_index', 'wsrep_local_state', 'wsrep_local_state_comment', 'wsrep_ready', 'wsrep_replicated', 'wsrep_replicated_bytes');" if credentials are in a custom path: mysql --defaults-file=/path/to/.my.cnf -s -e And run it with: watch sh /tmp/xx If single node alive (ERROR 1047 WSREP has not yet prepared node for application use): …

To prevent bloking the cluster while doing ALTERS (SCHEMA UPGRADES), do this per node: SET wsrep_OSU_method='RSU'; Then Run the ALTER statement once done reset the Schema Upgrade method back to Total Order Isolation. SET wsrep_OSU_method='TOI'; http://galeracluster.com/documentation-webpages/clusterstallonalter.html http://galeracluster.com/documentation-webpages/schemaupgrades.html …

Create 12 GB tmp disk: hdiutil create -o /tmp/Mojave.cdr -size 12000m -layout SPUD -fs HFS+J Attach the disk: hdiutil attach /tmp/Mojave.cdr.dmg -noverify -mountpoint /Volumes/install_build Extract the installer: sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/install_build Create the iso mv /tmp/Mojave.cdr.dmg ~/Desktop/InstallSystem.dmg hdiutil detach /Volumes/Install\ macOS\ Mojave hdiutil convert ~/Desktop/InstallSystem.dmg -format UDTO -o ~/Desktop/Mojave.iso Rename Mojave.iso.cdr to Mojave.iso …

softwareupdate -l to see if there are macOS updates available. softwareupdate -ia to install all updates. sudo jamf policy to run all outstanding policies and updates for the apps, sudo jamf recon to update the inventory on the server. …

If reset can’t clean your terminal, give a try to: stty sane …

Set window title: <c-b>, Get pannel number: <c-b>q Show clock: <c-b>t Move pane to a new window: <c-b>! Join panes: <c-b>: join-pane -s 0 -t 3 move pane 1 to window 3 <c-b>: join-pane -t :1 move current pane to window 1 Create a new session: <c-b>: new -s <name> List sessions: <c-b>s <c-b>w expanded Move pane to a another session: <c-b>m mark the pane <c-b>w go to the destination window/session <c-b>: join-pane or go to the pane you want to move, check the session name and windows you would like to move and try: …

To block incoming ssh connections, edit the /etc/pf.conf and add the following line at the bottom: block in log quick proto tcp from any to any port 22 You can use vim or use something like this: sudo sh -c "echo 'block in log quick proto tcp from any to any port 22' >> /etc/pf.conf" Then reload the pfrules: sudo pfctl -Fa -f /etc/pf.conf For this to work the firewall must be enabled. …

Run show processlist every second: mysqladmin -uroot -p -i 1 processlist -i 1 stands for interval one second …

Beside the OSI/model, there is also the TCP/IP Model: Link Layer Internet (IP) Layer Transport Layer Application OSI Model The OSI model has a bit more granularity. Physical Layer Data Link Layer Network Layer (IP) Transport Layer (TCP) Session Layer (TLS) Presentation Layer Application Layer (HTTP) TLS establishes an encrypted session. In the OSI model this is where TLS operates. …

Change password password in irc: /msg nickserv set password <password> …

Combine in a single file 2 images: convert +append a.png b.png out.png -append will append vertically instead of horizontally (+) …

To remove the blinking of symbolic links when doing ls in Linux: LS_COLORS="ln=35" export LS_COLORS That will set the ln=35 symbolic links to color purple. Params for LS_COLORS: di Directory fi File ln Symbolic Link pi Fifo file so Socket file bd Block (buffered) special file cd Character (unbuffered) special file or Symbolic Link pointing to a non-existent file (orphan) mi Non-existent file pointed to by a symbolic link (visible when you type ls -l) ex File which is executable (ie. …

To create an htpasswd file (for htaccess “authentication”) using openssl: $ printf "foo:$(openssl passwd -apr1 PASSWORD)\n" >> .htpasswd If need to use crypt: $ printf "foo:$(openssl passwd -crypt PASSWORD)\n" >> .htpasswd …

To create a git repository and access to it via ssh: $ ssh your.host $ mkdir my-new-repo $ cd my-new-repo $ git --bare init To access your repo (clone it): $ git clone ssh://[email protected]:2222/~user/my-new-repo …

Create a self signed CA (Certificate Authority) Generate private key: $ openssl genrsa -des3 -out CA.key 4096 To create a private key without password: $ openssl genrsa -out CA.key 4096 Create a root certificate: $ openssl req -x509 -new -nodes -key CA.key -sha256 -out CA.pem -subj "/CN=example.com" -days 365 In one single command create the private key and the certificate: $ openssl req -x509 -newkey rsa:4096 -sha256 -nodes -keyout CA. …

BOSH is a project that unifies release engineering, deployment, and lifecycle management of small and large-scale cloud software. Check your environment: $ bosh env Set your deployment environment: $ export BOSH_DEPLOYMENT=foo if have multiple deployments in same dir better to use -d <deployment-name> since many commands are bound to this variable. To recreate your environment (virtualbox), remove the line that start with current_manifest from the file state. …

To add more swap on a ZFS system: # zfs create -V 64G -o org.freebsd:swap=on -o checksum=off -o compression=off -o dedup=off -o sync=disabled -o primarycache=none tank/swap2 To add it: # swapon /dev/zvol/tank/swap2 To resize you could first remove it: # swapoff /dev/zvol/tank/swap Then destroy it: # zfs destroy tank/swap …

To avoid having command in history just prefix them with an empty space: $⎵ uname If using zsh: $ echo "" > ~/.zsh_history & exec $SHELL -l …

To create an install disk using an spare disk: $ hdiutil create -size 6GB -fs JHFS+ -volname "macOS_installmedia" -type SPARSE ~/Desktop/macOS_installmedia Mount it (or double-click in Finder to mount): $ hdiutil mount ~/Desktop/macOS_installmedia.sparseimage Use the createinstallmedia: $ sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/macOS_installmedia --applicationpath /Applications/Install\ macOS\ High\ Sierra.app …