Use stdbuf to tee without buffering

Do you want to tee the output of a command to a file, but see it in your terminal too, without buffering? The stdbuf command can do this for you:

$ sudo stdbuf --output=L tcpdump -i any -tttt -n 'udp port 5353' | tee -a tcpdump-mdns
tcpdump: data link type LINUX_SLL2
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on any, link-type LINUX_SLL2 (Linux cooked v2), snapshot length 262144 bytes
2023-06-15 11:55:16.637670 eth0 M   IP 10.0.0.23.5353 > 224.0.0.251.5353: 0 A (QM)? winnebago.local. (28)
2023-06-15 11:55:16.744660 eth0 M   IP 10.0.0.42.5353 > 224.0.0.251.5353: 0*- [0q] 1/0/0 (Cache flush) A 10.0.0.42 (38)
...

Which uninstalled package provides a file?

$ apt-file find guestmount
guestmount: /usr/bin/guestmount
guestmount: /usr/share/bash-completion/completions/guestmount
guestmount: /usr/share/doc/guestmount/changelog.Debian.gz
guestmount: /usr/share/doc/guestmount/copyright
guestmount: /usr/share/man/ja/man1/guestmount.1.gz
guestmount: /usr/share/man/man1/guestmount.1.gz
guestmount: /usr/share/man/uk/man1/guestmount.1.gz

Scripting DNS lookups

Are you writing a script and some command doesn’t accept hostnames and you don’t want to inline the IP address? dig +short is your friend!

$ dig +short gbenson.net
69.163.152.201

Which APT repository did a package come from?

$ apt policy wget
wget:
  Installed: 1.21.2-2ubuntu1
  Candidate: 1.21.2-2ubuntu1
  Version table:
 *** 1.21.2-2ubuntu1 500
        500 http://gb.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
        100 /var/lib/dpkg/status

Container debugging minihint

What’s in my container?

$ podman ps --ns
CONTAINER ID  NAMES            PID    CGROUPNS  IPC         MNT         NET         PIDNS       USERNS      UTS
fe11359293e8  eloquent_austin  11090            4026532623  4026532621  4026532421  4026532624  4026531837  4026532622

$ sudo ls -l /proc/11090/root/
total 22628
lrwxrwxrwx.   1 root root        7 Jul 25  2019 bin -> usr/bin
dr-xr-xr-x.   2 root root        6 Jul 25  2019 boot
drwxr-xr-x.   5 root root      360 Jan 24 12:03 dev
drwxr-xr-x.   1 root root      183 Jan 23 16:43 etc
 ...

Thank you.
[28 Jan@1135UTC] UPDATE—Actually, this doesn’t seem to work with newer systems, sorry!

Building GDB on a freshly installed machine FAQ

So you just installed Fedora, RHEL or CentOS and now you want to build GDB from source.

How do you make sure everything you need to build it is installed?
```
# dnf builddep gdb
```
Did it say, No such command: builddep? Do this, then try again:
```
# dnf install dnf-plugins-core
```
Did it say, dnf: command not found…? You’re using yum, try this:
```
# yum-builddep gdb
```
Did it say, yum-builddep: command not found…? Do this, then try again:
```
# yum install yum-utils
```

Thank you, you’re welcome.