1Any user that is a member of the wheel group can use "su -" to simulate 2a root login. You can add a user to the wheel group with: 3pw groupmod -n wheel -m user_name 4 -- Konstantinos Konstantinidis <kkonstan@duth.gr> 5% 6By pressing "Scroll Lock" you can use the arrow keys to scroll backward 7through the console output. Press "Scroll Lock" again to turn it off. 8Don't have a "Scroll Lock" key? The "Pause / Break" key acts alike. 9% 10Can't remember if you've installed a certain port or not? Try "pkg info 11-x port_name". 12% 13Ever wonder what those numbers after command names were, as in cat(1)? It's 14the section of the manual the man page is in. "man man" will tell you more. 15 -- David Scheidt <dscheidt@tumbolia.com> 16% 17Forget how to spell a word or a variation of a word? Use 18 19 look portion_of_word_you_know 20 -- Dru <genesis@istar.ca> 21% 22Forget what directory you are in? Type "pwd". 23 -- Dru <genesis@istar.ca> 24% 25Forget when Easter is? Try "ncal -e". If you need the date for Orthodox 26Easter, use "ncal -o" instead. 27 -- Dru <genesis@istar.ca> 28% 29FreeBSD is started up by the program 'init'. The first thing init does when 30starting multiuser mode (ie, starting the computer up for normal use) is to 31run the shell script /etc/rc. By reading /etc/rc and the /etc/rc.d/ scripts, 32you can learn a lot about how the system is put together, which again will 33make you more confident about what happens when you do something with it. 34% 35Handy bash(1) prompt: PS1="\u@\h \w \!$ " 36 -- David Scheidt <dscheidt@tumbolia.com> 37% 38Having trouble using fetch through a firewall? Try setting the environment 39variable FTP_PASSIVE_MODE to yes, and see fetch(3) for more details. 40% 41If other operating systems have damaged your Master Boot Record, you can 42reinstall it with gpart(8). See 43"man gpart" for details. 44% 45If you accidentally end up inside vi, you can quit it by pressing Escape, colon 46(:), q (q), bang (!) and pressing return. 47% 48If you do not want to get beeps in X11 (X Windows), you can turn them off with 49 50 xset b off 51% 52If you have a CD-ROM drive in your machine, you can make the CD-ROM that is 53presently inserted available by typing 'mount /cdrom' as root. The CD-ROM 54will be available under /cdrom/. Remember to do 'umount /cdrom' before 55removing the CD-ROM (it will usually not be possible to remove the CD-ROM 56without doing this.) 57 58Note: This tip may not work in all configurations. 59% 60If you need a reminder to leave your terminal, type "leave +hhmm" where 61"hhmm" represents in how many hours and minutes you need to leave. 62 -- Dru <genesis@istar.ca> 63% 64If you need to ask a question on the FreeBSD-questions mailing list then 65 66 https://docs.freebsd.org/en/articles/freebsd-questions 67 68contains lots of useful advice to help you get the best results. 69% 70If you write part of a filename in tcsh, 71pressing TAB will show you the available choices when there 72is more than one, or complete the filename if there's only one match. 73% 74If you `set watch = (0 any any)' in tcsh, you will be notified when 75someone logs in or out of your system. 76% 77If you use the C shell, add the following line to the .cshrc file in your 78home directory to prevent core files from being written to disk: 79 80 limit coredumpsize 0 81 -- Dru <genesis@istar.ca> 82% 83If you want df(1) and other commands to display disk sizes in 84kilobytes instead of 512-byte blocks, set BLOCKSIZE in your 85environment to 'K'. You can also use 'M' for Megabytes or 'G' for 86Gigabytes. If you want df(1) to automatically select the best size 87then use 'df -h'. 88% 89If you want to play CDs with FreeBSD, a utility for this is already included. 90Type 'cdcontrol' then 'help' to learn more. (You may need to set the CDROM 91environment variable in order to make cdcontrol want to start.) 92% 93If you'd like to keep track of applications in the FreeBSD ports tree, take a 94look at FreshPorts; 95 96 https://www.freshports.org/ 97% 98In order to make fetch (the FreeBSD downloading tool) ask for 99username/password when it encounters a password-protected web page, you can set 100the environment variable HTTP_AUTH to 'basic:*'. 101% 102In order to search for a string in some files, use 'grep' like this: 103 104 grep "string" filename1 [filename2 filename3 ...] 105 106This will print out the lines in the files that contain the string. grep can 107also do a lot more advanced searches - type 'man grep' for details. 108% 109In order to support national characters for European languages in tools like 110less without creating other nationalisation aspects, set the environment 111variable LC_ALL to 'en_US.UTF-8'. 112% 113"man firewall" will give advice for building a FreeBSD firewall using ipfw(8). 114 -- David Scheidt <dscheidt@tumbolia.com> 115% 116"man hier" will explain the way FreeBSD filesystems are normally laid out. 117 -- David Scheidt <dscheidt@tumbolia.com> 118% 119Man pages are divided into section depending on topic. There are 9 different 120sections numbered from 1 (General Commands) to 9 (Kernel Developer's Manual). 121You can get an introduction to each topic by typing 122 123 man <number> intro 124 125In other words, to get the intro to general commands, type 126 127 man 1 intro 128% 129"man ports" gives many useful hints about installing FreeBSD ports. 130% 131"man security" gives very good advice on how to tune the security of your 132FreeBSD system. 133% 134"man tuning" gives some tips how to tune performance of your FreeBSD system. 135 -- David Scheidt <dscheidt@tumbolia.com> 136% 137Need to do a search in a manpage or in a file you've sent to a pager? Use 138"/search_word". To repeat the same search, type "n" for next or "p" for 139previous. 140 -- Dru <genesis@istar.ca> 141% 142Need to find the location of a program? Use "locate program_name". 143 -- Dru <genesis@istar.ca> 144% 145Need to leave your terminal for a few minutes and don't want to logout? 146Use "lock -p". When you return, use your password as the key to unlock the 147terminal. 148 -- Dru <genesis@istar.ca> 149% 150Need to quickly empty a file? Use ": > filename". 151 -- Dru <genesis@istar.ca> 152% 153Need to quickly return to your home directory? Type "cd". 154 -- Dru <genesis@istar.ca> 155% 156Need to remove all those ^M characters from a DOS file? Try 157 158 tr -d \\r < dosfile > newfile 159 -- Originally by Dru <genesis@istar.ca> 160% 161Need to see the calendar for this month? Simply type "cal". To see the 162whole year, type "cal -y". 163 -- Dru <genesis@istar.ca> 164% 165Need to see which daemons are listening for connection requests? Use 166"sockstat -4l" for IPv4, and "sockstat -l" for IPv4 and IPv6. 167 -- Dru <genesis@istar.ca> 168% 169Need to see your routing table? Type "netstat -rn". The entry with the G 170flag is your gateway. 171 -- Dru <genesis@istar.ca> 172% 173Nice bash prompt: PS1='(\[$(tput md)\]\t <\w>\[$(tput me)\]) $(echo $?) \$ ' 174 -- Mathieu <mathieu@hal.interactionvirtuelle.com> 175% 176Over quota? "du -sh * | sort -h " will give you a sorted list of your 177directory sizes. 178 -- David Scheidt <dscheidt@tumbolia.com> 179% 180nc(1) (or netcat) is useful not only for redirecting input/output to 181TCP or UDP connections, but also for proxying them with inetd(8). 182% 183sh (the default Bourne shell in FreeBSD) supports command-line editing. Just 184``set -o emacs'' or ``set -o vi'' to enable it. Use "<TAB>" key to complete 185paths. 186% 187Simple tcsh prompt: set prompt = '%# ' 188% 189The default editor in FreeBSD is vi, which is efficient to use when you have 190learned it, but somewhat user-unfriendly. To use ee (an easier but less 191powerful editor) instead, set the environment variable EDITOR to /usr/bin/ee 192% 193Time to change your password? Type "passwd" and follow the prompts. 194 -- Dru <genesis@istar.ca> 195% 196To change an environment variable in /bin/sh use: 197 198 $ VARIABLE="value" 199 $ export VARIABLE 200% 201To change an environment variable in tcsh you use: setenv NAME "value" 202where NAME is the name of the variable and "value" its new value. 203% 204To clear the screen, use "clear". To re-display your screen buffer, press 205the scroll lock key and use your page up button. When you're finished, 206press the scroll lock key again to get your prompt back. 207 -- Dru <genesis@istar.ca> 208% 209You can press Ctrl-L while in the shell to clear the screen. 210% 211To determine whether a file is a text file, executable, or some other type 212of file, use 213 214 file filename 215 -- Dru <genesis@istar.ca> 216% 217To do a fast search for a file, try 218 219 locate filename 220 221locate uses a database that is updated every Saturday (assuming your computer 222is running FreeBSD at the time) to quickly find files based on name only. 223% 224To erase a line you've written at the command prompt, use "Ctrl-U". 225 -- Dru <genesis@istar.ca> 226% 227To find out the hostname associated with an IP address, use 228 229 drill -x IP_address 230 -- Dru <genesis@istar.ca> 231% 232To obtain a neat PostScript rendering of a manual page, use ``-t'' switch 233of the man(1) utility: ``man -t <topic>''. For example: 234 235 man -t grep > grep.ps # Save the PostScript version to a file 236or 237 man -t printf | lp # Send the PostScript directly to printer 238% 239To quickly create an empty file, use "touch filename". 240 -- Dru <genesis@istar.ca> 241% 242To read a compressed file without having to first uncompress it, use 243"zcat" or "zless" to view it. There is also "bzcat", "bzless", "xzcat" 244and "xzless". 245 -- Dru <genesis@istar.ca> 246% 247To save disk space in your home directory, compress files you rarely 248use with "gzip filename". 249 -- Dru <genesis@istar.ca> 250% 251To search for files that match a particular name, use find(1); for example 252 253 find / -name "*GENERIC*" -ls 254 255will search '/', and all subdirectories, for files with 'GENERIC' in the name. 256 -- Stephen Hilton <nospam@hiltonbsd.com> 257% 258To see all of the directories on your FreeBSD system, type 259 260 find / -type d | less 261 262All the files? 263 264 find / -type f | less 265% 266To see how long it takes a command to run, type the word "time" before the 267command name. 268 -- Dru <genesis@istar.ca> 269% 270To see how much disk space is left on your UFS partitions, use 271 272 df -h 273 -- Dru <genesis@istar.ca> 274% 275To see the 10 largest files in a directory or on a UFS partition, use 276 277 du -h /partition_or_directory_name | sort -rh | head 278 -- Dru <genesis@istar.ca> 279% 280To see the IP addresses currently set on your active interfaces, type 281"ifconfig -u". 282 -- Dru <genesis@istar.ca> 283% 284To see the last 10 lines of a long file, use "tail filename". To see the 285first 10 lines, use "head filename". To see new lines as they're appended 286to a file, use "tail -f filename". 287 -- Dru <genesis@istar.ca> 288% 289To see the last time that you logged in, use lastlogin(8). 290 -- Dru <genesis@istar.ca> 291% 292To see the MAC addresses of the NICs on your system, type 293 294 ifconfig -a 295 -- Dru <genesis@istar.ca> 296% 297To see the output from when your computer started, run dmesg(8). If it has 298been replaced with other messages, look at /var/run/dmesg.boot. 299 -- Francisco Reyes <lists@natserv.com> 300% 301Want colour in your directory listings? Use "ls -G". "ls -F" is also useful, 302and they can be combined as "ls -FG". 303% 304Want to find a specific port? Just type the following under /usr/ports 305or one of its subdirectories: 306 307 make search name=<port-name> 308 or 309 make search key=<keyword> 310% 311Want to know how many words, lines, or bytes are contained in a file? Type 312"wc filename". 313 -- Dru <genesis@istar.ca> 314% 315Want to see how much virtual memory you're using? Just type "swapinfo" to 316be shown information about the usage of your swap partitions. 317% 318Want to strip UTF-8 BOM(Byte Order Mark) from given files? 319 320 sed -e '1s/^\xef\xbb\xbf//' < bomfile > newfile 321% 322Want to use sed(1) to edit a file in place? Well, to replace every 'e' with 323an 'o', in a file named 'foo', you can do: 324 325 sed -i.bak s/e/o/g foo 326 327And you'll get a backup of the original in a file named 'foo.bak', but if you 328want no backup: 329 330 sed -i '' s/e/o/g foo 331% 332When you've made modifications to a file in vi(1) and then find that 333you can't write it, type ``<ESC>!rm -f %'' then ``:w!'' to force the 334write 335 336This won't work if you don't have write permissions to the directory 337and probably won't be suitable if you're editing through a symbolic link. 338 339If you have sudo(8) installed and permissions to use it, type 340``<ESC>w ! sudo tee %'' to force a write. 341% 342You can adjust the volume of various parts of the sound system in your 343computer by typing 'mixer <type>.volume=<volume>%'. To get a list of what 344you can adjust, just type 'mixer'. 345% 346You can automatically download and install binary packages by doing 347 348 pkg install <package> 349 350This will also automatically install the packages that are dependencies 351for the package you install (ie, the packages it needs in order to work.) 352% 353You can change the video mode on all consoles by adding something like 354the following to /etc/rc.conf: 355 356 allscreens="80x30" 357 358You can use "vidcontrol -i mode | grep T" for a list of supported text 359modes. 360 -- Konstantinos Konstantinidis <kkonstan@duth.gr> 361% 362You can disable tcsh's terminal beep if you `set nobeep'. 363% 364You can install extra packages for FreeBSD by using the ports system. 365If you have installed it, you can download, compile, and install software by 366just typing 367 368 # cd /usr/ports/<category>/<portname> 369 # make install && make clean 370 371as root. The ports infrastructure will download the software, change it so 372it works on FreeBSD, compile it, install it, register the installation so it 373will be possible to automatically uninstall it, and clean out the temporary 374working space it used. You can remove an installed port you decide you do not 375want after all by typing 376 377 # cd /usr/ports/<category>/<portname> 378 # make deinstall 379 380as root. 381% 382You can look through a file in a nice text-based interface by typing 383 384 less filename 385% 386You can make a log of your terminal session with script(1). 387% 388You can often get answers to your questions about FreeBSD by searching in the 389FreeBSD mailing list archives at 390 391 https://lists.freebsd.org/search 392% 393You can open up a new split-screen window in (n)vi with :N or :E and then 394use ^w to switch between the two. 395% 396You can permanently set environment variables for your shell by putting them 397in a startup file for the shell. The name of the startup file varies 398depending on the shell - csh and tcsh uses .login, bash, sh, ksh and zsh use 399.profile. When using bash, sh, ksh or zsh, don't forget to export the 400variable. 401% 402You can press Ctrl-D to quickly exit from a shell, or logout from a 403login shell. 404 -- Konstantinos Konstantinidis <kkonstan@duth.gr> 405% 406You can press up-arrow or down-arrow to walk through a list of 407previous commands in tcsh. 408% 409You can search for documentation on a keyword by typing 410 411 apropos keyword 412% 413You can `set autologout = 30' to have tcsh log you off automatically 414if you leave the shell idle for more than 30 minutes. 415% 416You can use aliases to decrease the amount of typing you need to do to get 417commands you commonly use. Examples of fairly popular aliases include (in 418Bourne shell style, as in /bin/sh, bash, ksh, and zsh): 419 420 alias lf="ls -FA" 421 alias ll="ls -lA" 422 alias su="su -m" 423 424In csh or tcsh, these would be 425 426 alias lf ls -FA 427 alias ll ls -lA 428 alias su su -m 429 430To remove an alias, you can usually use 'unalias aliasname'. To list all 431aliases, you can usually type just 'alias'. 432% 433You can use /etc/make.conf to control the options used to compile software 434on this system. Example entries are in 435/usr/share/examples/etc/make.conf and in make.conf(5). 436For options that are set for building FreeBSD's kernel and its world, see 437src.conf(5). 438% 439You can use "pkg info" to see a list of packages you have installed. 440% 441You can use the 'fetch' command to retrieve files over ftp, http or https. 442 443 fetch https://www.FreeBSD.org/images/beastie.png 444 445will download the beastie image from the FreeBSD web site. 446% 447You can use "whereis" to search standard binary, manual page and source 448directories for the specified programs. This can be particularly handy 449when you are trying to find where in the ports tree an application is. 450 451Try "whereis firefox" and "whereis whereis". 452 -- Konstantinos Konstantinidis <kkonstan@duth.gr> 453% 454Want to run the same command again? 455In many shells (e.g., tcsh, zsh, bash) you can type "!!". 456% 457Want to go the directory you were just in? 458Type "cd -" 459% 460Can't delete /usr/obj? Enter "chflags -R noschg /usr/obj" to remove the 461system immutable flag for all files in /usr/obj. 462 463 -- Lars Engels <lme@FreeBSD.org> 464% 465Want to list all files of an installed package? Enter 466"pkg info -l packagename". 467 468 -- Lars Engels <lme@FreeBSD.org> 469% 470Are you looking for a package? Search for it with 471"pkg search part_of_package_name" 472 473 -- Lars Engels <lme@FreeBSD.org> 474% 475If you want to recursively copy a directory preserving file and directory 476attributes use 477"cp -a source target" 478 479 -- Lars Engels <lme@FreeBSD.org> 480% 481Do you wonder what a terminal program is doing at the moment? dd(1) does not 482show any throughput? Hit "^T" (Control + t) to send SIGINFO to the process 483and see what it is doing. 484 485 -- Lars Engels <lme@FreeBSD.org> 486% 487Do you want to know which version of FreeBSD you are running? Enter 488"freebsd-version -ku" to display kernel and userland version. 489 490 -- Lars Engels <lme@FreeBSD.org> 491% 492If you want to end one or more processes at a time using a regular expression 493enter "pkill regex". 494 495 -- Lars Engels <lme@FreeBSD.org> 496% 497Do you want to run a program directly after some other process has ended? Use 498"pwait pid && new_program" 499 500 -- Lars Engels <lme@FreeBSD.org> 501% 502When you want your users to be able to reboot or shutdown FreeBSD, add them 503to the group "operator" and they are allowed to use shutdown(8) and poweroff(8). 504 505 -- Lars Engels <lme@FreeBSD.org> 506% 507If you need to create a FAT32 formatted USB thumb drive, find out its devicename 508running dmesg(8) after inserting it. Then create an MBR schema, a single slice and 509format it: 510 511# gpart create -s MBR ${devicename} 512# gpart add -t fat32 ${devicename} 513# newfs_msdos -F 32 -L thumbdrive ${devicename}s1 514 515 -- Lars Engels <lme@FreeBSD.org> 516% 517If you want to get a sorted list of all services that are started when FreeBSD boots, 518enter "service -e". 519 520 -- Lars Engels <lme@FreeBSD.org> 521% 522To easily configure your installed FreeBSD use bsdconfig(8). 523 524 -- Lars Engels <lme@FreeBSD.org> 525% 526After you compiled and installed a new version of FreeBSD, use etcupdate(8) to merge 527configuration updates. 528Run "etcupdate extract" once when your sources match your running system, then run 529"etcupdate" after every upgrade and "etcupdate resolve" to resolve any conflicts. 530 531 -- Lars Engels <lme@FreeBSD.org> 532% 533Do you want to do a binary upgrade of your running FreeBSD installation? Use freebsd-update(8). 534 535To install updates and patches for the running branch use 536# freebsd-update fetch 537# freebsd-update install 538 539Then, to upgrade to a newer release use 540# freebsd-update upgrade -r ${name_of_release} 541 542 -- Lars Engels <lme@FreeBSD.org> 543% 544To run rc scripts in /etc/rc.d and /usr/local/etc/rc.d use service(8). 545Run "service ${name_of_rc_script} start" to start a daemon and 546"service ${name_of_rc_script} stop" to stop it. 547 548 -- Lars Engels <lme@FreeBSD.org> 549% 550If you don't want to edit /etc/rc.conf directly, use sysrc(8) to add and remove entries. 551Use "sysrc name=value" to add an entry and "sysrc -x name" to delete an entry. 552 553 -- Lars Engels <lme@FreeBSD.org> 554% 555You can upload the dmesg of your system to help developers get an overview of commonly 556used hardware and peripherals for FreeBSD. Use the curl package to upload it like this: 557curl -v -d "nickname=$USER" -d "description=FreeBSD/$(uname -m) on \ 558$(kenv smbios.system.maker) $(kenv smbios.system.product)" -d "do=addd" \ 559--data-urlencode 'dmesg@/var/run/dmesg.boot' http://dmesgd.nycbug.org/index.cgi 560% 561Want to know how much memory (in bytes) your machine has installed? Let 562sysctl(8) tell you with the following command: 563 564sysctl hw.realmem 565 566The realmem value is memory before the kernel and modules are loaded, whereas 567hw.physmem is what is left after they were loaded. 568 569The number of active CPUs is displayed using this command: 570 571sysctl hw.ncpu 572 573 -- Benedict Reuschling <bcr@FreeBSD.org> 574% 575When using ZFS as the file system the "df" command is reporting the pool size 576and not file system sizes. It also does not know about descendent ZFS 577datasets, snapshots, quotas, and reservations with their individual space usage. 578Use the built-in "zfs list" command to get a better overview of space usage: 579 580zfs list -o space 581 582 -- Benedict Reuschling <bcr@FreeBSD.org> 583% 584To learn more about what your system is doing, take a look at systat(1). For 585example, to get various statistics related to virtual memory usage, process 586scheduling, device interrupts, system name translation caching, and disk I/O, 587enter the following: 588 589systat -vmstat 590 591Other values are icmp, icmp6, ifstat, iostat, ip, ip6, netstat, pigs, sctp, 592swap, tcp, or zarc. You can switch between displays using :<display> and exit 593back to your shell by typing 594 595:quit 596 597 -- Benedict Reuschling <bcr@FreeBSD.org> 598% 599To set a quota of 10 GB for the user named foo on a ZFS dataset, run the 600following command: 601 602# zfs set userquota@foo=10G pool/home/foo 603 604The zfs userspace command can display the quota and current space usage: 605 606# zfs userspace pool/home/foo 607 608To unset a quota, assign "none" as the value. 609 -- Benedict Reuschling <bcr@FreeBSD.org> 610% 611ZFS can display I/O statistics for a given pool using the iostat subcommand. 612By default, it will display one line of current activity. To display stats 613every 5 seconds run the following command (cancel with CTRL+C): 614 615zpool iostat 5 616 617To view individual disk activities, specify the -v parameter: 618 619zpool iostat -v 620 621Of course, both can be combined. For more options, see zpool(8). 622 -- Benedict Reuschling <bcr@FreeBSD.org> 623% 624FreeBSD's top(1) utility displays CPU statistics by default. 625To display I/O activity for each process instead, run top like this: 626 627top -m io 628 629 -- Benedict Reuschling <bcr@FreeBSD.org> 630% 631ZFS keeps a history of commands run against a specific pool using the 632history subcommand to zpool: 633 634zpool history 635 636More details are available using the -i and -l parameters. Note that ZFS 637will not keep the complete pool history forever and will remove older 638events in favor of never ones. 639 -- Benedict Reuschling <bcr@FreeBSD.org> 640% 641To display the compression ratio for the ZFS dataset /var/log on the pool 642mypool, run the following command: 643 644zfs get refcompressratio mypool/var/log 645 646The refcompressratio will only display the compression ratio for that specific 647dataset, not the descendant datasets. To include the child datasets, the 648command looks like this: 649 650zfs get compressratio mypool/var 651 652 -- Benedict Reuschling <bcr@FreeBSD.org> 653% 654You can limit the depth of the displayed datasets in the "zfs list" output 655using the -d parameter. To display only the first level of datasets below 656mypool/usr and not the ones deeper than those, run this command: 657 658zfs list -d 1 mypool/usr 659 660 -- Benedict Reuschling <bcr@FreeBSD.org> 661% 662The "zfs list" command can be filtered in multiple ways. To display just 663the dataset name, use the -o parameter: 664 665zfs list -o name mypool/usr 666 667More columns and their order can be defined by separating them with commas: 668 669zfs list -o mountpoint,name,avail 670 671 -- Benedict Reuschling <bcr@FreeBSD.org> 672% 673The output of "zfs list" can be sorted by a specific column using -s. To 674sort the datasets by the "used" column in ascending order, run this command: 675 676zfs list -s used 677 678To sort in descending order instead, use -S: 679 680zfs list -S used 681 682 -- Benedict Reuschling <bcr@FreeBSD.org> 683% 684To make the "zfs list" output more script-friendly, you can suppress the 685output of the headers for each column by passing the -H parameter: 686 687zfs list -H 688 689Another helpful option for script writers is -p, which displays the numbers 690in non-rounded, exact values: 691 692zfs list -p 693 694 -- Benedict Reuschling <bcr@FreeBSD.org> 695% 696Before deleting a dataset or snapshot, perform a dry run using the -n 697parameter. This is to make sure you really want to delete just that 698dataset/snapshot and not any dependent ones. ZFS will display the resulting 699action when -n is combined with the -v option without actually performing 700it: 701 702zfs destroy -nrv mypool@mysnap 703 704Once you are sure this is exactly what you intend to do, remove the -n 705parameter to execute the destroy operation. 706 -- Benedict Reuschling <bcr@FreeBSD.org> 707% 708You can delete a range of ZFS snapshots (a-z) in multiple ways. 709The following will delete d and all earlier snapshots: 710 711zfs destroy mypool/data@%d 712 713To delete d and all later snapshots: 714 715zfs destroy mypool/data@d% 716 717To delete all dataset snapshots: 718 719zfs destroy mypool/data@% 720 721Make sure to let ZFS perform a dry run (-n option) first and display (-v) what 722it would do to confirm that the delete operation is removing exactly what you 723intended. 724 -- Benedict Reuschling <bcr@FreeBSD.org> 725% 726To set a custom ZFS property on the mypool pool, you need to provide it 727using the "key1:key2=value" syntax, where the colon (:) is used as the 728separator and identifier from the built-in ZFS properties: 729 730# zfs set warranty:expires=2038-01-19 mypool 731 732The custom property is applied to all datasets and can be queried like any 733built-in properties using zfs get: 734 735zfs get warranty:expires mypool 736 737To reset the value of a custom property, use the inherit subcommand: 738 739# zfs inherit warranty:expires mypool 740 741Removing a custom property from a pool is done using the -r flag to the 742"zfs inherit" command: 743 744# zfs inherit -r warranty:expires mypool 745 746 -- Benedict Reuschling <bcr@FreeBSD.org> 747% 748To delete a range of ZFS snapshots, use the % (percent) character after the 749full path to the first snapshot that should be included. For example, to 750simulate deleting snapshots a through (including) d, use this command: 751 752# zfs destroy -rvn mypool/tmp@a%d 753 754Once you are sure that this is what you want, remove the -n option: 755 756# zfs destroy -rv mypool/tmp@a%d 757 758 -- Benedict Reuschling <bcr@FreeBSD.org> 759% 760You can prevent the removal of a ZFS snapshot by using the hold subcommand. 761For example, to prevent the snapshot called milestone from deletion, run the 762following command: 763 764# zfs hold milestone_hold mypool/projects@my_milestone 765 766The "zfs holds" command will list all current snapshots that are protected 767this way (-r for a recursive list): 768 769# zfs holds -r mypool 770 771The TIMESTAMP column in the output of the above command is from when the 772hold was created, not the snapshot it holds. The "zfs destroy" command will 773echo a "dataset is busy" message on the console when it encounters a hold. 774Use "zfs release" to release the hold on the snapshot: 775 776# zfs release milestone_hold mypool/projects@my_milestone 777 778 -- Benedict Reuschling <bcr@FreeBSD.org> 779% 780A user "sender" needs the following permissions set to send a ZFS dataset: 781 782# zfs allow -u sender send,snapshot txpool 783 784On the receiving side, the user "receiver" requires these permissions: 785 786# zfs allow -u receiver compression,mountpoint,mount,create,receive rxpool 787 788 -- Benedict Reuschling <bcr@FreeBSD.org> 789% 790Don't let your zpool fill up completely by creating a dataset with 791reservation. 792 793# zfs create -o refreservation=<5% of total pool space> <poolname>/reserved 794 795You can always shrink the reserve if you need the space, but your pool will 796always have space left this way. 797 798 -- Benedict Reuschling <bcr@FreeBSD.org> 799% 800Sometimes a single slow HDD can cripple the performance of your entire system. 801You can spot one like this: 802 803# gstat -I5s | sort -rn -k9 | head 804 805 -- Alan Somers <asomers@FreeBSD.org> 806% 807FreeBSD's ps(1) can create a dependency tree based on parent/child 808relationships between processes, like this: 809 810$ ps -d 811 812 -- Daniel Ebdrup Jensen <debdrup@FreeBSD.org> 813% 814It is possible to measure the resident memory set: 815 816$ vmstat -o | awk 'NR>1 { t[$7] += $1 } \ 817END { for (i in t) printf "%s %d\n",i,t[i] }' 818 819The rows have the following meaning: 820df = default (not assigned a specific pager) 821sw = swap 822df = virtual 823vn = vnode 824ph = heap 825md = memory device 826 827This will be reported in number of pages, so it needs to be multiplied by the 828page size of the architecture which can be found via: 829 830$ sysctl -n hw.pagesize 831 832 -- Daniel Ebdrup Jensen <debdrup@FreeBSD.org> 833% 834To establish a serial connection to anything including a USB device, 835nothing more than cu(1) is needed: 836 837$ cu -s 115200 -l /dev/ttyU0 838 839 -- Daniel Ebdrup Jensen <debdrup@FreeBSD.org> 840% 841You can control kernel stack(9) traces on ^T (tty info) by setting 842kern.tty_info_kstacks to 0 (off), 1 (on), or 2 (verbose), e.g.: 843 844# sysctl kern.tty_info_kstacks=2 845 846 -- Michael Gmelin <grembo@FreeBSD.org> 847% 848To determine which fonts provide a particular Unicode character, fc-list from 849the fontconfig package may be helpful. For example, if your friend complains 850that the emoji you sent won't display, run fc-list with the hex value of the 851character to determine which font your friend should install. 852 853$ fc-list ':charset=0x1F4A1' 854/usr/local/share/fonts/noto/NotoColorEmoji.ttf: Noto Color Emoji:style=Regular 855 856$ pkg which /usr/local/share/fonts/noto/NotoColorEmoji.ttf 857/usr/local/share/fonts/noto/NotoColorEmoji.ttf was installed by package noto-emoji-2.042 858% 859When netstat reports every 8 seconds, it tells traffic in bits per second: 860 861$ netstat -I bge0 8 862% 863