Diff of the two buildlogs:

--
--- b1/build.log	2025-03-18 18:58:37.393970873 +0000
+++ b2/build.log	2025-03-18 18:59:07.864593302 +0000
@@ -1,6 +1,6 @@
 I: pbuilder: network access will be disabled during build
-I: Current time: Tue Mar 18 06:55:45 -12 2025
-I: pbuilder-time-stamp: 1742324145
+I: Current time: Tue Apr 21 15:21:39 +14 2026
+I: pbuilder-time-stamp: 1776734499
 I: Building the build Environment
 I: extracting base tarball [/var/cache/pbuilder/unstable-reproducible-base.tgz]
 I: copying local configuration
@@ -22,52 +22,84 @@
 dpkg-source: info: unpacking c2x_2.42+ds-1.debian.tar.xz
 I: using fakeroot in build.
 I: Installing the build-deps
-I: user script /srv/workspace/pbuilder/90412/tmp/hooks/D02_print_environment starting
+I: user script /srv/workspace/pbuilder/1677931/tmp/hooks/D01_modify_environment starting
+debug: Running on ionos15-amd64.
+I: Changing host+domainname to test build reproducibility
+I: Adding a custom variable just for the fun of it...
+I: Changing /bin/sh to bash
+'/bin/sh' -> '/bin/bash'
+lrwxrwxrwx 1 root root 9 Apr 21 01:21 /bin/sh -> /bin/bash
+I: Setting pbuilder2's login shell to /bin/bash
+I: Setting pbuilder2's GECOS to second user,second room,second work-phone,second home-phone,second other
+I: user script /srv/workspace/pbuilder/1677931/tmp/hooks/D01_modify_environment finished
+I: user script /srv/workspace/pbuilder/1677931/tmp/hooks/D02_print_environment starting
 I: set
-  BUILDDIR='/build/reproducible-path'
-  BUILDUSERGECOS='first user,first room,first work-phone,first home-phone,first other'
-  BUILDUSERNAME='pbuilder1'
-  BUILD_ARCH='amd64'
-  DEBIAN_FRONTEND='noninteractive'
-  DEB_BUILD_OPTIONS='buildinfo=+all reproducible=+all parallel=20 '
-  DISTRIBUTION='unstable'
-  HOME='/root'
-  HOST_ARCH='amd64'
+  BASH=/bin/sh
+  BASHOPTS=checkwinsize:cmdhist:complete_fullquote:extquote:force_fignore:globasciiranges:globskipdots:hostcomplete:interactive_comments:patsub_replacement:progcomp:promptvars:sourcepath
+  BASH_ALIASES=()
+  BASH_ARGC=()
+  BASH_ARGV=()
+  BASH_CMDS=()
+  BASH_LINENO=([0]="12" [1]="0")
+  BASH_LOADABLES_PATH=/usr/local/lib/bash:/usr/lib/bash:/opt/local/lib/bash:/usr/pkg/lib/bash:/opt/pkg/lib/bash:.
+  BASH_SOURCE=([0]="/tmp/hooks/D02_print_environment" [1]="/tmp/hooks/D02_print_environment")
+  BASH_VERSINFO=([0]="5" [1]="2" [2]="37" [3]="1" [4]="release" [5]="x86_64-pc-linux-gnu")
+  BASH_VERSION='5.2.37(1)-release'
+  BUILDDIR=/build/reproducible-path
+  BUILDUSERGECOS='second user,second room,second work-phone,second home-phone,second other'
+  BUILDUSERNAME=pbuilder2
+  BUILD_ARCH=amd64
+  DEBIAN_FRONTEND=noninteractive
+  DEB_BUILD_OPTIONS='buildinfo=+all reproducible=+all parallel=42 '
+  DIRSTACK=()
+  DISTRIBUTION=unstable
+  EUID=0
+  FUNCNAME=([0]="Echo" [1]="main")
+  GROUPS=()
+  HOME=/root
+  HOSTNAME=i-capture-the-hostname
+  HOSTTYPE=x86_64
+  HOST_ARCH=amd64
   IFS=' 	
   '
-  INVOCATION_ID='61067967fc924cd18716e8c46638b972'
-  LANG='C'
-  LANGUAGE='en_US:en'
-  LC_ALL='C'
-  MAIL='/var/mail/root'
-  OPTIND='1'
-  PATH='/usr/sbin:/usr/bin:/sbin:/bin:/usr/games'
-  PBCURRENTCOMMANDLINEOPERATION='build'
-  PBUILDER_OPERATION='build'
-  PBUILDER_PKGDATADIR='/usr/share/pbuilder'
-  PBUILDER_PKGLIBDIR='/usr/lib/pbuilder'
-  PBUILDER_SYSCONFDIR='/etc'
-  PPID='90412'
-  PS1='# '
-  PS2='> '
+  INVOCATION_ID=3443841272de4a3a9cc441ddac58fdf7
+  LANG=C
+  LANGUAGE=et_EE:et
+  LC_ALL=C
+  MACHTYPE=x86_64-pc-linux-gnu
+  MAIL=/var/mail/root
+  OPTERR=1
+  OPTIND=1
+  OSTYPE=linux-gnu
+  PATH=/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path
+  PBCURRENTCOMMANDLINEOPERATION=build
+  PBUILDER_OPERATION=build
+  PBUILDER_PKGDATADIR=/usr/share/pbuilder
+  PBUILDER_PKGLIBDIR=/usr/lib/pbuilder
+  PBUILDER_SYSCONFDIR=/etc
+  PIPESTATUS=([0]="0")
+  POSIXLY_CORRECT=y
+  PPID=1677931
   PS4='+ '
-  PWD='/'
-  SHELL='/bin/bash'
-  SHLVL='2'
-  SUDO_COMMAND='/usr/bin/timeout -k 18.1h 18h /usr/bin/ionice -c 3 /usr/bin/nice /usr/sbin/pbuilder --build --configfile /srv/reproducible-results/rbuild-debian/r-b-build.yXZuGM7m/pbuilderrc_2OR4 --distribution unstable --hookdir /etc/pbuilder/first-build-hooks --debbuildopts -b --basetgz /var/cache/pbuilder/unstable-reproducible-base.tgz --buildresult /srv/reproducible-results/rbuild-debian/r-b-build.yXZuGM7m/b1 --logfile b1/build.log c2x_2.42+ds-1.dsc'
-  SUDO_GID='111'
-  SUDO_UID='106'
-  SUDO_USER='jenkins'
-  TERM='unknown'
-  TZ='/usr/share/zoneinfo/Etc/GMT+12'
-  USER='root'
-  _='/usr/bin/systemd-run'
-  http_proxy='http://46.16.76.132:3128'
+  PWD=/
+  SHELL=/bin/bash
+  SHELLOPTS=braceexpand:errexit:hashall:interactive-comments:posix
+  SHLVL=3
+  SUDO_COMMAND='/usr/bin/timeout -k 24.1h 24h /usr/bin/ionice -c 3 /usr/bin/nice -n 11 /usr/bin/unshare --uts -- /usr/sbin/pbuilder --build --configfile /srv/reproducible-results/rbuild-debian/r-b-build.yXZuGM7m/pbuilderrc_jf7X --distribution unstable --hookdir /etc/pbuilder/rebuild-hooks --debbuildopts -b --basetgz /var/cache/pbuilder/unstable-reproducible-base.tgz --buildresult /srv/reproducible-results/rbuild-debian/r-b-build.yXZuGM7m/b2 --logfile b2/build.log c2x_2.42+ds-1.dsc'
+  SUDO_GID=111
+  SUDO_UID=106
+  SUDO_USER=jenkins
+  TERM=unknown
+  TZ=/usr/share/zoneinfo/Etc/GMT-14
+  UID=0
+  USER=root
+  _='I: set'
+  http_proxy=http://213.165.73.152:3128
 I: uname -a
-  Linux ionos11-amd64 6.1.0-32-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.129-1 (2025-03-06) x86_64 GNU/Linux
+  Linux i-capture-the-hostname 6.12.12+bpo-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.12.12-1~bpo12+1 (2025-02-23) x86_64 GNU/Linux
 I: ls -l /bin
-  lrwxrwxrwx 1 root root 7 Mar  4 11:20 /bin -> usr/bin
-I: user script /srv/workspace/pbuilder/90412/tmp/hooks/D02_print_environment finished
+  lrwxrwxrwx 1 root root 7 Mar  4  2025 /bin -> usr/bin
+I: user script /srv/workspace/pbuilder/1677931/tmp/hooks/D02_print_environment finished
  -> Attempting to satisfy build-dependencies
  -> Creating pbuilder-satisfydepends-dummy package
 Package: pbuilder-satisfydepends-dummy
@@ -137,7 +169,7 @@
 Get: 30 http://deb.debian.org/debian unstable/main amd64 debhelper all 13.24.1 [920 kB]
 Get: 31 http://deb.debian.org/debian unstable/main amd64 libsymspg2 amd64 2.6.0-1 [194 kB]
 Get: 32 http://deb.debian.org/debian unstable/main amd64 libsymspg-dev amd64 2.6.0-1 [37.4 kB]
-Fetched 21.1 MB in 7s (3116 kB/s)
+Fetched 21.1 MB in 2s (10.4 MB/s)
 Preconfiguring packages ...
 Selecting previously unselected package sensible-utils.
 (Reading database ... 
(Reading database ... 5%
(Reading database ... 10%
(Reading database ... 15%
(Reading database ... 20%
(Reading database ... 25%
(Reading database ... 30%
(Reading database ... 35%
(Reading database ... 40%
(Reading database ... 45%
(Reading database ... 50%
(Reading database ... 55%
(Reading database ... 60%
(Reading database ... 65%
(Reading database ... 70%
(Reading database ... 75%
(Reading database ... 80%
(Reading database ... 85%
(Reading database ... 90%
(Reading database ... 95%
(Reading database ... 100%
(Reading database ... 19784 files and directories currently installed.)
@@ -285,7 +317,11 @@
 fakeroot is already the newest version (1.37.1-1).
 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
 I: Building the package
-I: Running cd /build/reproducible-path/c2x-2.42+ds/ && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" HOME="/nonexistent/first-build" dpkg-buildpackage -us -uc -b && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" HOME="/nonexistent/first-build" dpkg-genchanges -S  > ../c2x_2.42+ds-1_source.changes
+I: user script /srv/workspace/pbuilder/1677931/tmp/hooks/A99_set_merged_usr starting
+Not re-configuring usrmerge for unstable
+I: user script /srv/workspace/pbuilder/1677931/tmp/hooks/A99_set_merged_usr finished
+hostname: Name or service not known
+I: Running cd /build/reproducible-path/c2x-2.42+ds/ && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path" HOME="/nonexistent/second-build" dpkg-buildpackage -us -uc -b && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path" HOME="/nonexistent/second-build" dpkg-genchanges -S  > ../c2x_2.42+ds-1_source.changes
 dpkg-buildpackage: info: source package c2x
 dpkg-buildpackage: info: source version 2.42+ds-1
 dpkg-buildpackage: info: source distribution unstable
@@ -295,7 +331,7 @@
  debian/rules clean
 dh clean
    dh_auto_clean
-	make -j20 clean
+	make -j42 clean
 make[1]: Entering directory '/build/reproducible-path/c2x-2.42+ds'
 rm -f c2x check2xsf.o check_read.o xsf_write.o molecule_fix.o cube_write.o cell_read.o periodic_table.o basis.o super.o xplor_write.o pdb_write.o cell_write.o dx_write.o vasp_write.o pdb_read.o xyz_write.o cml_write.o fdf_write.o gpfa.o rotate.o chdiff_read.o esp_read.o interpolate.o line_write.o shelx_read.o shelx_write.o fbin_write.o ident_sym.o primitive.o ksym.o f15.o cif_write.o cube_read.o cif_read.o c2x2spg.o sort_atoms.o py_write.o xsf_read.o vasp_read.o denfmt_write.o denfmt_read.o parse.o dipole.o fort34_read.o crystal_read.o abinit_read.o abinit_write.o abinit_in_read.o fdf_read.o qe_write.o qe_read.o parity.o potential.o qe_rho_read.o qe_xml_read.o dict.o charge.o qe_psi_read.o print_cell.o bands_write.o geom_write.o xv_read.o rho_read.o tube.o ccp4_write.o xc.o band_process.o gcoeff_write.o wavecar_write.o bxsf_write.o bands_read.o xyz_read.o gcoeff_read.o elk_write.o elk_read.o geom_read.o npy_read.o npy_write.o file_read.o data_combine.o dx_read.o mol_read.o mol_write.o zones.o grad.o band_plot.o dos.o bravais_sc.o phonon_read.o
 make[1]: Leaving directory '/build/reproducible-path/c2x-2.42+ds'
@@ -306,7 +342,7 @@
    dh_autoreconf
    dh_auto_configure
    dh_auto_build
-	make -j20 "INSTALL=install --strip-program=true"
+	make -j42 "INSTALL=install --strip-program=true"
 make[1]: Entering directory '/build/reproducible-path/c2x-2.42+ds'
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o check2xsf.o check2xsf.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o check_read.o check_read.c
@@ -366,10 +402,6 @@
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o dict.o dict.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o charge.o charge.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o qe_psi_read.o qe_psi_read.c
-vasp_read.c: In function 'vasp_read':
-vasp_read.c:206:13: warning: '*<unknown>' may be used uninitialized [-Wmaybe-uninitialized]
-  206 |   if(!nionsp[nspec-1])
-      |       ~~~~~~^~~~~~~~~
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o print_cell.o print_cell.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o bands_write.o bands_write.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o geom_write.o geom_write.c
@@ -394,6 +426,10 @@
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o data_combine.o data_combine.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o dx_read.o dx_read.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o mol_read.o mol_read.c
+vasp_read.c: In function 'vasp_read':
+vasp_read.c:206:13: warning: '*<unknown>' may be used uninitialized [-Wmaybe-uninitialized]
+  206 |   if(!nionsp[nspec-1])
+      |       ~~~~~~^~~~~~~~~
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o mol_write.o mol_write.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o zones.o zones.c
 gcc -Wall -Wno-unused-result -O -g -DSPGLIB -I.  -c -o grad.o grad.c
@@ -425,8 +461,8 @@
    dh_gencontrol
    dh_md5sums
    dh_builddeb
-dpkg-deb: building package 'c2x-dbgsym' in '../c2x-dbgsym_2.42+ds-1_amd64.deb'.
 dpkg-deb: building package 'c2x' in '../c2x_2.42+ds-1_amd64.deb'.
+dpkg-deb: building package 'c2x-dbgsym' in '../c2x-dbgsym_2.42+ds-1_amd64.deb'.
  dpkg-genbuildinfo --build=binary -O../c2x_2.42+ds-1_amd64.buildinfo
  dpkg-genchanges --build=binary -O../c2x_2.42+ds-1_amd64.changes
 dpkg-genchanges: info: binary-only upload (no source code included)
@@ -434,12 +470,14 @@
 dpkg-buildpackage: info: binary-only upload (no source included)
 dpkg-genchanges: info: including full source code in upload
 I: copying local configuration
+I: user script /srv/workspace/pbuilder/1677931/tmp/hooks/B01_cleanup starting
+I: user script /srv/workspace/pbuilder/1677931/tmp/hooks/B01_cleanup finished
 I: unmounting dev/ptmx filesystem
 I: unmounting dev/pts filesystem
 I: unmounting dev/shm filesystem
 I: unmounting proc filesystem
 I: unmounting sys filesystem
 I: cleaning the build env 
-I: removing directory /srv/workspace/pbuilder/90412 and its subdirectories
-I: Current time: Tue Mar 18 06:58:36 -12 2025
-I: pbuilder-time-stamp: 1742324316
+I: removing directory /srv/workspace/pbuilder/1677931 and its subdirectories
+I: Current time: Tue Apr 21 15:22:07 +14 2026
+I: pbuilder-time-stamp: 1776734527