Operating Systems
Writing operating systems
POSIX
Standards
Minix
Android
Keystore
# Create a keystore
keytool -genkey -v -keystore /path/to/example-key.keystore -keyalg RSA -keysize 2048 -alias alias_name -validity 10000
# Get expiration dates in the store
keytool -list -v -keystore keystore.jks
Auto-sign release
Add to ant.properties
key.store=/path/to/example-key.keystore
key.alias=alias_name
Solaris
This includes Solaris derivatives as well, such as OpenSolaris and the Illumos project http://www.brendangregg.com/blog/2017-09-05/solaris-to-linux-2017.html
Solaris
SMF (Service Management Facility)
Clear maintenance mode and restart
svcadm clear <FMRI>
List services
svcs -a
Logs
/var/svc/log
Links
Sun OpenBoot
Boot from CDROM
boot cdrom
Test hardware
test-all
Show banner
banner
Get ethernet address
.enet-addr
Show hardware devices
show-devs
SmartOS
- vmadm - start, stop, etc virtual machines
- imgadm - find, download, install images
SmartDataCenter
Find VM by alias
| sdc-vmapi *vms | json -H -c “this.alias && this.alias.match(/riak*)” |
Output fwapi rules
sdc-fwapi /rules
Update resolvers
sdc-vmapi /vms/?action=update -d '{ "resolvers": ["8.8.8.8", "8.8.4.4"]}'
OmniOS
OpenBSD
List PCI devices
pcidump -v
Install package
pkg_add <package>
Add an IP alias to a network interface
ifconfig carp0 inet alias 192.0.1.2 netmask 255.255.255.255
Delete an IP alias
ifconfig carp0 delete 192.0.1.2
Download ports
cd /usr
cvs get ports
USB snapshots
dd if=install*.fs of=/dev/sd1c bs=1m
Updates
# See installed patches
syspatch -l
# See uninstalled patches
syspatch -c
# Install any uninstalled patches
syspatch
Securelevels
Edit /etc/rc.securelevel or sysctl kern.securelevel
| num | desc |
|---|---|
| -1 | permanently insecure |
| 0 | insecure |
| 1 | secure |
| 2 | highly secure |
Building from source
See man 8 release
OpenBSD ld.so
# get documentation
man ld.so
# get information about what is getting loaded at run-time
LD_DEBUG=1 ./a.out
trunk
Setup
ifconfig bge0 up
ifconfig bge1 up
ifconfig trunk0 trunkport <proto> bge0 trunkport bge1 \
192.168.1.1 netmask 255.255.255.0
| proto | desc |
|---|---|
| failover | Fails over to next link |
| lacp | increases link speed and redundancy, requires lacp-capable switch |
| loadbalance | load-balancing |
| roundrobin | Use round-robin scheduler to distribute traffic |
CARP
master advertises on port 112
ifconfig syntax
ifconfig carpN create
ifconfig carpN [advbase n] [advskew n] [balancing mode] \
[carpnodes vhid:advskew,vhid:advskew,...] [carpdev iface] \
[[-]carppeer peer_address] [pass passphrase] [state state] [vhid host-id]
Try to become master
# Force master to give up control
ifconfig carp0 down
# Allow preemption
sysctl net.inet.carp.preempt=1
pf
pfctl
| flag | command |
|---|---|
| -e | Enable pf |
| -d | Disable pf |
| -nf | parse file, don’t load |
| -f | load pf.conf file |
| -sr | show rulesets |
| -ss | show state table |
| -si | show filter stats+counters |
| -sl | show label counters |
| -sa | show everything |
General rule syntax
action [direction] [log] [quick] [on interface] [af] [proto protocol] \
[from src_addr [port src_port]] [to dst_addr [port dst_port]] \
[flags tcp_flags] [state]
| action | pass/block |
|---|---|
| direction | in/out |
| quick | if packet matches rule, do action and skip rest of rules |
| af (address family) | inet/inet6 |
| protocol | udp/tcp/icmp |
($ext_if) is shorthand for “use the IP address for the rule” (handy with NAT)
Default deny
block in all
block out all
Table containing all IP addresses to firewall
table <firewall> const { self }
Resources
pfsync
sysctl
net.inet.carp.preempt=1
ifconfig
ifconfig em1 10.10.10.2 netmask 255.255.255.0
ifconfig pfsync0 syncdev em1
ifconfig pfsync0 up
Conferences
- AsiaBSDCon
- BSDCan
- All Systems Go
Darwin
iOS (Apple)
Reboot phone (iPhone 8+)
- Quickly press and let go of the volume up button
- Quickly press and let go of the volume down button
- Press and hold the right side button until reboot
View lifecycle
- viewDidLoad
- viewWillAppear
- viewDidAppear
- vieWillDisappear
- viewDidDisappear
iOS web programming
Web Inspector
-
On Mac
Safari -> Preferences -> Advanced -> Show Develop in menu bar
-
On iPhone
Settings -> Safari -> Advanced -> Web Inspector
Application Name
<title>WebApp</title>
Launcher icon (iOS 1.1.3+)
Rounded corners, no added shiny (iOS 4.2):
<link rel="apple-touch-icon-precomposed" href="apple-touch-icon-precomposed.png"/>
Added shiny:
<link rel="apple-touch-icon" href="touch-icon-iphone.png" />
<link rel="apple-touch-icon" sizes="72x72" href="touch-icon-ipad.png" />
<link rel="apple-touch-icon" sizes="114x114" href="touch-icon-iphone4.png" />
With no sizes the default is 57x57 px
(Multiple sizes iOS 4.2+)
Startup Image (iOS 3.0+)
<link rel="apple-touch-startup-image" href="/startup.png">
320x460 px, portrait
Have standalone look
<meta name="apple-mobile-web-app-capable" content="yes" />
You might think it’s an innocent meta tag, but in fact it’s a powerful and dangerous meta tag if you add it irresponsibly. You must provide a single page application solution offering back buttons inside the UI -or use location.href instead of normal links if you don’t want them to be opened in the browser instead of your app’s container-. https://medium.com/@firt/dont-use-ios-web-app-meta-tag-irresponsibly-in-your-progressive-web-apps-85d70f4438cb
That will involve: a) adding back navigation everywhere, b) create a SPA experience or use location.href instead of links for internal navigation, c) if the load process is done in fullscreen mode (navigator.standalone==true), always load the home screen not matter what the stored URL says and please d) don’t suggest me to “download an app” if I’m already inside an app-like experience.
Hide top status bar
NB - must have standalone mode on.
<meta name="apple-mobile-web-app-status-bar-style" content="black" />
Prevent zooming
<meta name="viewport" content="initial-scale=1.0">
<meta name="viewport" content="maximum-scale=1.0">
<meta name="viewport" content="user-scalable=no">
<meta name="viewport" content="width=device-width">
Links
watchOS
watchOS app bundled in iOS app 
Complications
The visual element on the watchface
- useful for frequently used info
- app stays in memory
- app receives more time to execute background tasks
- Aople recommends creating a complication, even if it is only a button to launch the app
Notifications
short look - glanceable version of notification content if the wrist remains raised, goes to long look
UI
Key color
- The title string in the status bar
- App name in short-look notifications
stored in Global Tint property of an app’s storyboad
Page-based navigation
Add interface controllers
Links
tvOS
https://developer.apple.com/documentation/tvservices https://developer.apple.com/documentation/avkit https://developer.apple.com/documentation/mediaplayer https://developer.apple.com/documentation/tvmljs
osquery
Get processes where the path no longer exists
select pid,path,uid from processes where on_disk=0;
Plan 9 from Bell Labs
Fuchsia
https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main
PRIMOS OS
built in FORTRAN