# Freebsd ## Freebsd boot process ### Why compile kernel for booting /running on hardware with limited resources for testing a patch and provide feedback to devs for diabling sth when there is a conflict to support my unsupported hardware ### Smashing The Stack For Fun And Profit def:paper attempts to explain what buffer overflows are, and how their exploits work. :::info something useful but not directly related: virtual memory experience with gdb ::: On many C implementations it is possible to corrupt the execution stack by writing past the end of an array declared auto in a routine. Code that does this is said to smash the stack, and can cause return from the routine to jump to a random address. # How did unix/linux identify a file? 前言:在windows中，一個檔案後面都會附帶一串由一個點和一串文字所組成的後綴，這個機制稱為副檔名，for example：.txt、.word...等，這個機制讓作業系統能夠辨識一個檔案的特徵和做更進一步的使用，而在unix/linux並沒有附檔名的機制，那linux是使用什麼樣的方式來辨別一個檔案? ## Definition meta data embedded in the file itself that identifies the file type 被嵌入在檔案中用來偵測檔案類別的元資料。 可以使用file(1)命令來檢查一個檔案的格式。 ```terminal= man magic ``` ## what is rc file? * *def: a data placement structure that determines how to store relational tables on computer clusters* ## Nvidia drivers install nvidia-xconfig will make xorg totally render on the display card.If we got two display driver,nvidia-xconfig will make an xorg.conf and take over the control of the display. ``` nvidia-xconfig ``` ## What I have done this week I created a bugzilla account ## ports dependancy I accidentally break my dependancy on gettext ``` ``` Example 3. Failover Mode Between Ethernet and Wireless Interfaces # 顯卡安裝 先安裝intel核心顯卡驅動i915kms， ```shell= pkg install drm-kmod ``` 安裝顯卡後分為兩種情況，是否支援獨顯直連，如果不支援，需要先安裝i915kms在安裝 ```shell= $ pkg install nvidia-hybrid-graphics $ pkg install nvidia-secondary-driver $ pkg install nvidia-secondary-driver $ sysrc kld_list+=nvidia-modeset $ sysrc nvidia_xorg_enable=YES $ nvrun 程式名稱 # 無GUI執行 $ nvrun-vgl 程式名稱# 以GUI 執行 ``` 獨顯直連： ```shell pkg install nvidia-driver nvidia-settings nvidia-xconfig nvidia-drm-kmod sysrc kld_list+="nvidia-modeset nvidia-drm.ko" ``` 最後可以安裝mesa-demos作為測試 nvrun-vgl bounce # Mounting iso image ``` $ mdconfig freebsd.iso md0 $ mount_cd9660 /dev/md0 /mnt/iso $ umount /mnt/iso $ mdconfig -d /dev/md0 ``` # Generating iso image (debian) ```sh # Install required tools pkg install gcpio cdrkit-genisoimage # Download Debian iso image and untar fetch https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-12.5.0-amd64-netinst.iso tar -C isofiles -xf debian-12.5.0-amd64-netinst.iso # Feed preseed if needed chmod -R +w isofiles/install.amd/ gunzip isofiles/install.amd/initrd.gz echo preseed.cfg | gcpio -H newc -o -A -F isofiles/install.amd/initrd gzip isofiles/install.amd/initrd chmod -R -w isofiles/install.amd/ # Generate hash chmod +w isofiles/md5sum.txt find -L isofiles -type f ! -name isofiles/md5sum.txt -print0 | xargs -0 md5 | tee isofiles/md5sum.txt chmod -w isofiles/md5sum.txt # Generate image cd isofiles genisoimage -r -J -b isolinux/isolinux.bin \ -c isolinux/boot.cat \ -no-emul-boot -boot-load-size 4 -boot-info-table \ -o preseed-debian-12.5.0-netinst.iso . ``` ### network server #### Inetd * Super-Server * only needs to start inetd for many other application * when connection to a service managed by inetd, * inetd decides destination and spawns a process for that program, and delegates the program a socket. * Using inetd for services that are not heavily used can reduce system load, when compared to running each daemon individually in stand-alone mode.